Schedule and Locations

Advanced LIGO has provided dramatic new insights into the relativistic objects that populate the Universe via all-sky surveys during its first three observing runs whilst radio surveys continue to discover both radio pulsars in relativistic binaries and millisecond-duration flashes known as Fast Radio Bursts. In this talk I will review some of the more interesting discoveries pertaining to relativistic gravity and Fast Radio Bursts, and where these fields are heading in the 2020s and 2030s.

Since the first discovery of gravitational waves in 2015, Australia has played an important role in the real-time detection and follow-up of gravitational wave events. During the upcoming 4th LIGO-Virgo-KAGRA observing run O4, UWA’s SPIIR pipeline is one of the five ‘online’ pipelines that will provide real-time public alerts of gravitational wave events. I will discuss the upgrades to the SPIIR pipeline that will have the potential to deliver breakthrough discoveries in O4, and the opportunities for the Australian astronomy community to exploit our unique location and facilities to follow-up real-time and pre-merger alerts of gravitational wave events.

Bars are more common than not in low-redshift disc galaxies, yet we tend to ignore their effects when modelling galaxies. This oversight neglects the very real influence of bars on the stellar populations, kinematics, and star formation location and duration in galaxies. We undertake a detailed analysis into the effect of a bar on its host galaxy by comparing 245 barred galaxies from the MaNGA galaxy survey to a mass- and morphology-matched control sample of unbarred galaxies. At fixed stellar mass and morphology, barred galaxies are optically redder than their unbarred counterparts. From stellar population analysis using the full spectral fitting code STARLIGHT, we attribute this difference to both older and more metal-rich stellar populations. The star formation histories of barred galaxies peak earlier than their non-barred counterparts, and the galaxies build up their mass at earlier times. We speculate on the mechanisms that have allowed barred galaxies to be older, more metal-rich and more gas-poor today, including the efficient redistribution of galactic fountain byproducts, and a runaway bar formation scenario in gas-poor discs. While the `chicken or the egg’ analogy is apt in describing the coincidence of large bars and gas poor discs in observations, we can conclude that regardless of which came first, barred galaxies lived fast and died young.

The Large and Small Magellanic Clouds (LMC/SMC), as two of the closest and most massive satellites of the Milky Way, have significant effects on the local Universe; including on the orbits of tidal streams, and on the distribution of ultra-faint satellites. However their masses, and interaction history beyond the most recent LMC/SMC close passage, remain poorly constrained. In this talk, I will discuss the Magellanic Edges Survey (MagES), which kinematically maps the extremely low-surface-brightness periphery of the Clouds, in order to shed light on these issues. We use a combination of Gaia astrometry and spectroscopically-derived radial velocities, obtained with 2dF+AAOmega on the Anglo-Australian Telescope, to determine the first 3D kinematics for a wealth of stellar substructure extending to distances beyond 23 degrees from the Clouds’ centres. Our initial results focus on the LMC. We reveal a large northern substructure that, due to its discrepant kinematics relative to the LMC disk, was likely formed during a recent interaction with the Milky Way; and several structures in the southwestern LMC that new dynamical models reveal were likely formed in an interaction with the SMC ~400Myr ago. This is the first kinematic constraint on the dynamical history of the Clouds prior to their most recent close passage, and represents an enormous step forward in understanding their complex interactions. These results demonstrate the efficacy of MagES as a benchmark for assessing dynamical models to shed light on both the origin of Magellanic substructures, and the evolution of the Magellanic/Milky Way system.

SN 2017jgh is a type IIb supernova discovered by Pan-STARRS during the C16/C17 campaigns of the Kepler/K2 mission. The 30-minute cadence of Kepler/K2 along with ground based observations of SN 2017jgh captured the shock cooling of the progenitor shock breakout, the first moments after explosion. This presents a unique opportunity to investigate the progenitors of stripped envelope supernovae, with only a handful being measured to-date. By fitting analytical models to the SN 2017jgh lightcurve, we find that the progenitor of SN 2017jgh was likely a yellow supergiant. We also use the lightcurve of SN 2017jgh to investigate how effective early observations of the rise of the shock cooling curve are in cons tainting the progenitor star’s properties. We find that without the rise, the explosion time is poorly constrained, leading to systematic offsets in the shock velocity, and larger uncertainties in the mass and radius of the progenitor.

Understanding the behavior of white dwarfs in interacting binary systems is critical to determining the rates of optical transients such as novae and type Ia supernovae, as well as the evolutionary pathways leading to these events. By incorporating the latest results from detailed models, we can study the impact of these works on the observable universe from a population statistics perspective, allowing us to compare our modern understanding of binary evolution against the reality of the observed rates of these transients. I will describe the overarching physical framework used in my recently published population synthesis work on novae, and present several interesting insights into the lives of these systems.

When a star passes too close to a supermassive black hole (SMBH) it can be destroyed, temporarily increasing the accretion rate onto the SMBH. Such tidal disruption events (TDEs) produce bright flares across the electromagnetic spectrum that provide a unique window into the central region of a galaxy, including the previously dormant black hole. Radio observations of TDEs are uncommon (with only 9 TDEs with published radio detections), and probe the lower-energy outflows and jets that may be produced in these energetic events. Whilst observations of TDEs at optical and X-ray wavelengths have confirmed much about the disk formation, super-Eddington accretion, and details of SMBHs that can disrupt stars, the driving force behind the differences in radio properties of TDEs is not well-known, and nor is the nature of the mechanism powering the outflows that may be produced. Some outflows appear as highly collimated relativistic jets, whilst others present slower-moving, dispersed outflows that could be explained by a sub-relativistic jet, non-relativistic wind, or unbound tidal debris streams. In this talk I will present the most detailed broadband spectral observations of a non-relativistic radio outflow from a TDE, AT2019azh, to date, with 13 epochs of observations spanning two years post optical discovery. These observations, taken with the Very Large Array, enable us to place constraints on the radius, minimum kinetic energy, velocity, magnetic field, and mass of the outflow. AT2019azh is unusual as it is continuing to brighten in the radio even 2 years post-disruption, posing questions about the central engine powering the outflow from this event and possibly enabling us to discriminate between different proposed outflow models. This work provides a significant addition to the state of radio observations of TDEs and will contribute to understanding the launching of jets and outflows from supermassive black holes.

X-ray binaries, containing a black hole or neutron star accreting from a stellar companion, are one of the few ways black holes can be studied. Globular clusters represent one of the best ways to study X-ray binaries as, due to high population densities, binaries are more likely to form through encounters between stars and compact objects. These dynamical interactions cause many unique X-ray binaries to form. There is a sizeable population of neutron stars in globular clusters, and while there should be an initial population of black holes in globular clusters due to their age, it was thought that the population would eventually be ejected from the cluster. Recent simulations have suggested that a population of black holes could survive in globular clusters, which has only recently been observationally confirmed with the detection of two black holes (and one candidate) in the cluster NGC 3201. With the release of the deepest radio and X-ray surveys to date of several dozen Galactic globular clusters (including NGC 3201), we are in a position to fully explore the population of X-ray binaries in clusters. In this talk, I will focus on the multi-wavelength observations of NGC 3201 covering from radio to X-rays and present the first radio and X-ray limits on the detached black holes in this cluster. I will discuss the implications that these limits have on the mass accretion rates of these black holes and the accretion efficiency, and how this contrasts with previous assumptions of the accretion efficiency. Finally, I will comment on the ability of current radio facilities to detect faint, accreting black holes in other Galactic globular clusters.

Neutron-star mergers have recently been confirmed as a site for rapid neutron- capture (r-) process nucleosynthesis. However, in Galactic chemical evolution models, neutron-star mergers alone fail to reproduce the element abundance patterns of extremely metal-poor stars, indicating other sites for r-process nucleosynthesis are required. Here we report the chemical abundance pattern of the highly r-process element enhanced, extremely metal-poor star SMSS J200322.54-114203.3, which has the lowest metallicity of all known r-process rich stars. The element abundance pattern in the star is well matched by the yields of a single 25 Msun magnetorotational hypernova: not only the r-process elements but also the light elements formed during massive star evolution and the iron-peak elements generated by explosive nuclear burning. Our results therefore indicate that magnetorotational hypernovae are an additional source of r-process nucleosynthesis that likely dominates r-process element production during the earliest epochs of star formation in the Galaxy.

We use comparisons between the Sydney-AAOMulti-object Integral Field Spectrograph (SAMI) Galaxy Survey and equilibrium galaxy models to infer the importance of disc fading in the transition of spirals into lenticular (S0) galaxies. The local S0 population has both higher photometric concentration and lower stellar spin than spiral galaxies of comparable mass and we test whether this separation can be accounted for by passive aging alone.We construct a suite of dynamically self-consistent galaxy models, with a bulge, disc, and halo using the GALACTICS code. The dispersion-dominated bulge is given a uniformly old stellar population, while the disc is given a current star formation rate putting it on the main sequence, followed by sudden instantaneous quenching. We then generate mock observables (r-band images, stellar velocity, and dispersion maps) as a function of time since quenching for a range of bulge/total (B/T) mass ratios. The disc fading leads to a decline in measured spin as the bulge contribution becomes more dominant, and also leads to increased concentration. However, the quantitative changes observed after 5Gyr of disc fading cannot account for all of the observed difference.We see similar results if we instead subdivide our SAMI Galaxy Survey sample by star formation (relative to the main sequence). We use EAGLE simulations to also take into account progenitor bias, using size evolution to infer quenching time. The EAGLE simulations suggest that the progenitors of current passive galaxies typically have slightly higher spin than present day star-forming disc galaxies of the same mass. As a result, progenitor bias moves the data further from the disc fading model scenario, implying that intrinsic dynamical evolution must be important in the transition from star-forming discs to passive discs.

The Deep Extragalactic VIsible Legacy Survey (DEVILS), is an ongoing spectroscopic survey on the AAT, with the aim of producing a deep, complete, galaxy redshift catalogue. With an expected sample of ~58,000 galaxies over 6 square degrees, this dataset will enable us to study the evolution of galaxies and groups at intermediate redshifts of 0.3 < z < 1.0, an epoch where spectroscopically complete samples of galaxies have not existed previously.
In this talk, I will present an overview of DEVILS, and it’s current status. Within the premier DEVILS field D10 (COSMOS), new datasets including multiwavelength photometry, SED-fitting outputs, morphological classifications, and bulge/disk decompositions have been produced. I will present the first science results using these data, following aspects of galaxy evolution, including the evolution of the star-forming main sequence and stellar mass density over 12 billion years of cosmic time, the precise derivation of the extragalactic background light from galaxy number counts, and the stellar mass growth of different morphological types since z~1. These sweeping studies of galaxy evolution with cosmic time are only now possible, because large datasets like DEVILS and GAMA have been analysed equivalently, facilitating a combined analysis of galaxy properties over broad redshift ranges.

MAGPI is the highest resolution spectroscopic survey of gas and stars beyond z=0. The goal of MAGPI, the first Australian-led ESO large program, is to determine the morphological, dynamical and chemical drivers of the evolution of galaxies by providing critical observations to connect primarily disky systems ~2 Gyr after Big Bang to well studied primarily passive local galaxies (e.g. SAMI/Hector). I will present an overview of the status of the MAGPI survey including the observations and early science results across the team with a focus on emission line science. I will detail the first results of characterising the fields including the excellent depth and resolution for identifying our primary sources and their satellites as well as numerous Lyman alpha emitters out to z~6. Our first results include a combination of gas and stellar kinematics in 5 fields of varying environmental density. We are an open survey and encourage all who are interested to get involved.

Thanks to recent advances in integral field spectroscopy (IFS), modern surveys are capable of resolving metallicity maps of nearby galaxies down to scales of∼50pc. However, statistical analysis of these metallicity maps has seldom gone beyond fitting basic linear regressions. In this talk, I will introduce several techniques from geostatistics, and apply them to a catalogue of high-resolution IFS observations of local spiral galaxies, in order to understand both the small- and large-scale structure of the interstellar medium (ISM). As a first application, we compare the results of this analysis to the predictions of a stochastic, physically motivated, analytical metal-transport model. Our results reveal that the ISMs of the observed galaxies are far less homogeneous than predicted, showing large metallicity fluctuations on ~1 kpc scales.

Mergers profoundly shape the evolution of galaxies over cosmic time. They are therefore critical events to study with large-scale spatially resolved spectroscopic surveys. The disruption caused by an interaction can be obvious, producing tidal tails, irregular morphologies, or disturbed kinematics. However this is not always the case – as these features are transient and have diverse appearances. Simulations, unlike observations, allow us to access to the time domain. We compute morphological and kinematic asymmetries at every time snapshot of a galaxy merger simulation suite run with the FIRE2 model. We find that mergers are least detectable in the pair phase, with only 40% showing kinematic asymmetry, while almost all are detected during the merger and post-coalescence. We also quantify the effects of the differing fields of view of SAMI, HECTOR, and MUSE. We find that it becomes extremely difficult to detect galaxy pairs with smaller FoVs, but that merging and post-coalescence galaxies suffer less. We show that combining morphological and kinematic measures of asymmetry improves your ability to detect mergers and mitigate the limitations of smaller fields of view.

In order to simultaneously explain the observed mass of present-day galaxies and that of those in the early Universe (i.e. 10-11 billion years ago), models of that evolution predict large mass losses during the interaction processes. Thus, a significant number of stars initially belonging to each galaxy must be ripped out with every interaction. Those stars congregate in diffuse ensembles that sprawl across the centres of galaxy clusters where galaxy interactions are more likely, forming a so-called intra-cluster light (ICL) component. As galaxies spend most of their lives in groups, the intra-group light (IGL) that forms during interactions within these environments is the predecessor of the ICL in clusters of galaxies. Unveiling the quantity and origin of both ICL and IGL, forms a fossil record of all the dynamical processes a system has undergone and provides a holistic view of a group’s interaction history. The diffuse nature of the IGL makes it to be typically detected at very low surface brightnesses, so its study is a technical challenge. In this work, we examine Galaxy And Mass Assembly (GAMA) survey groups within Hyper-Suprime Cam (HSC) Subaru Strategic Program Public Data Release 2. We will present our ongoing results on the first IGL measurements from HSC data. We compare these results with theoretical predictions to infer the dominant source in the formation of this important component so as, the mass assembly history of the host group.

Modelling of FRB measurements is commonly performed either to study the FRB population(s) – its luminosity function, cosmological evolution, broad spectral properties, and the nature of its repeating sources – or to analyse cosmological properties of our Universe, e.g. the baryonic matter fraction and its distribution in halos, and the Hubble constant. I begin by first highlighting the interconnectedness of these two measurements: both attempt to model the distribution of FRBs in redshift-dispersion measure (z-DM) space, a draw conclusions from this. I then note how observational biases need to be modelled to allow accurate parameter estimates, and present the results of a maximum likelihood analysis on the FRB population using measurements from the Parkes and ASKAP telescopes. In particular, the FRB population is found to be evolving with redshift in a manner consistent with the star-formation rate.

Short gamma-ray bursts (GRBs) are widely recognised to originate from binary neutron star mergers, especially after the coincident detection of GRB 170817A and GW 170817. Theory suggests that prompt (FRB-like) signals may be associated with neutron star mergers but this is still a poorly explored regime, particularly given the expected short timescales of the emission. Using the Murchison Widefield Array (MWA) rapid-response observing mode we are able to automatically and rapidly trigger on short GRBs within 30s of receiving an alert from Swift or Fermi in order to capture this predicted FRB-like emission. In this talk, I will present our results from a low frequency search for coherent radio emission from a sample of 10 short GRBs using MWA. We use the prompt emission fluence and persistent emission flux density limits derived from the 30min triggered observation of each of these GRBs to constrain the binary neutron star merger scenarios for FRB generation. Assuming the formation of a typical magnetar remnant by the merger, our results provide new insights into the emission models, i.e. either these GRBs are at high redshifts, these mergers form atypical magnetars, the radiation beams of the magnetar remnants are pointing away from us, or such mergers don’t form magnetars but rather directly collapse into black holes. In addition, we derive the most stringent prompt emission fluence limit (80-100Jy ms) to date on FRB-like signals produced by a short GRB from our observation of GRB 190627A, which has a known redshift of z=1.9. Assuming the formation of a stable magnetar for GRB 190627A, we place constraints on the key model parameters, i.e. the radio emission efficiency of the nearly merged neutron stars and the magnetar remnant, and the fraction of magnetic energy in the GRB jet, which were only poorly constrained under a presumed redshift in previous works.

Despite the frequency and high energy output of FRBs, what causes these bursts have eluded astronomers since their discovery over a decade ago. Information on emission coherent with the radio burst in other wavelengths can help reveal the physical processes that create these bursts. I present results from an observational program that can do this called the Deeper Faster Wider (DWF) program. During the September 2020 DWF observing run, two FRBs were detected with the Murriyang Radio Telescope (formerly known as the Parkes Radio Telescope). Simultaneously observing with Murriayng (before, during and after the FRB bursts) was the Neil Gehrels Swift Observatory, the Hard X-ray Modulation Telescope, AstroSat, the Korea Microlensing Telescope Network, the Huntsman Telescope, Murriyang and the Molonglo Observatory Synthesis Telescope, amongst others.

The Intergalactic Medium (IGM) is difficult to observe in the optical and UV due to the high temperatures (T ~ 10^6K) and low densities (n ~ 10^-6 cm^-3) leading to a lack of favourable transition lines. The dispersion measure (DM) of fast radio bursts (FRBs) provides a unique new way to probe the ionized baryons in the IGM. Cosmological models with different parameters lead to different DM-redshift (DM−z) relations. Additionally, the over/under-dense regions in the IGM and intervening galaxies’ circumgalactic medium lead to scattering around the mean DM−z relations. I will present the recent work I have published using the EAGLE simulations to study the DM-z relation, the scatter around it and the feasibility of FRBs to constrain galaxy feedback models. I find that almost all of the FRBs found at low-redshifts have significantly larger observed DMs than predicted from simulations, suggesting that many FRBs intersect filaments of the IGM. Additionally, I find that of the order 9000 localised FRBs will be required between redshifts z=0.5-1, to constrain the AGN feedback of galaxies.

Neutron stars are some of the most enigmatic and energetic phenomena in our Universe. Most known neutron stars have been detected via periodic radio or X-ray signals correlated with their rotational period, which are generated either by a conversion of a fraction of their spin-down dipole radiation (pulsars) or twisting and/or reorganisation of their intense magnetic fields (magnetars). The known population typically rotates with periods of milliseconds to tens of seconds, but it is postulated that these objects are vastly outnumbered by older, much more slowly-rotating neutron stars, which are thought to no longer generate emission. These “ultra-long period” (ULP) magnetars are candidate progenitors for Fast Radio Bursts, which themselves are now being localised to positions incompatible with young magnetars (e.g. globular clusters). ULP magnetars would explain many of the emission characteristics of FRBs, such as the quasi-periodic windows of emission, but were thought to be impossible to observe directly. We have detected the first ULP magnetar, using a low-frequency sky survey performed by the Murchison Widefield Array. Its radio emission is highly polarised and periodic on a timescale of ~20 minutes. Its dynamic spectrum shows high-fluence narrow-timescale “spikes” which are unresolved by our data, with fluence on par with FRBs generated by the Galactic centre magnetar. I will highlight the object’s main observational features, including its window of appearance, dispersion measure, polarisation attributes, and changes in its pulse profile over time. Along with X-ray and optical observations, these features have allowed us to constrain its physical attributes such as location in the Galaxy, radio luminosity, and likely magnetic field strength. I will conclude with a population estimate and thoughts on how we might best detect further examples, and follow them up to determine if they generate FRBs.

Multi-TeV cosmic rays (CRs) are trapped within the Milky Way by the Galactic magnetic field (GMF), and diffuse through the interstellar medium (ISM) for up to a hundred million years. This leads to a “sea” of particles around the Galactic plane, colloquially known as the TeV CR sea, which then leads to a sea of diffuse gamma-rays around the Galactic plane. Recent results from H.E.S.S., HAWC, and the Tibet Airshower Array show that this emission extends into the TeV and PeV energies, which presents a challenge for current and future imaging atmospheric Cherenkov telescopes such as the Cherenkov Telescope Array (CTA), which must subtract this background emission carefully to reveal discrete sources. In this contribution, we will discuss how the interstellar radiation field (ISRF), the Galactic magnetic field (GMF), and the CR source distribution within the Milky Way impact the TeV gamma-ray sea by utilising the three-dimensional simulation software GALPROP. A detailed, quantitative analysis of the TeV CR sea predicted by GALPROP is performed, and these predictions will be applied to results from the HESS TeV Galactic plane survey (HGPS), providing a comparison between CR diffusion models and the results from ground-based gamma-ray telescopes in this energy range.

The spatial distribution of oxygen in the interstellar medium of galaxies is key to understanding how efficiently metals that are created in the hearts of massive stars are mixed and redistributed across the galaxy. I present a study of 6 nearby spiral galaxies using the 3D optical data obtained in the TYPHOON Program. We use HIIPhot to identify the HII regions within the galaxy based on the surface brightness of the H-alpha luminosity and measure the radial variations of the HII region oxygen abundance. We recover a flattening to the negative radial gradient in several of the galaxies at large galactocentric radius, suggesting that we have sufficient resolution and sensitivity to detect the metallicity floor, which may be set by direct accretion of gas from the cosmic web. The measured metallicity floor informs on the chemical enrichment of the galaxy and the outflow of metals to the outer regions of the disk from the enriched inner region of the galaxy disk through radial flows. I will present comparisons with hydrodynamical simulations to shed light on the dynamical local enrichment of the oxygen enrichment in these galaxies.

Outflowing gas driven by star formation plays an important part in regulating the subsequent star formation. However the details of this star formation feedback process are still unclear, particularly in starbursting environments. To better constrain feedback models, high resolution IFU observations are needed to spatially resolve star-formation driven outflow properties and link these to co-located galaxy properties. I will present results from our pilot observations for the DUVET (Deep near-UV observations of Entrained gas in Turbulent galaxies) Survey of starbursting galaxies using the IFU Keck Cosmic Web Imager (KCWI). DUVET aims to use hyper-sensitive observations of starbursting disks to probe the subgrid physics of feedback models. We have measured the spatial distribution of outflows in these galaxies at sub-kpc resolution. Our pilot observations reveal that (1) outflows are ubiquitous in these galaxies, with all lines-of-sight having gas flows. (2) We find that for our pilot galaxy, two-thirds of the outflowing ionised gas mass originates from a peak which covers 10% of the galaxy area, and this peak is not co-located with the galaxy centre. (3) Using our observed outflows, we are able to discriminate between widely used models of feedback in galaxies. DUVET’s sub-kpc resolution observations allow us to rigorously test feedback prescriptions to help reveal how feedback regulates star formation.

The rapid decline in the average star formation activity of galaxies from z~2.6 to z~0 is accompanied by an order of magnitude decrease in the typical electron densities of HII regions. However, it is unclear what connects the pc-scale properties of the line-emitting gas with the global properties of the host galaxies. I will highlight recent results from a study of 611 galaxies at 0 < z < 2.6, drawn primarily from the KMOS^3D and SAMI surveys. We measure both the local electron density of the line-emitting gas and the volume-averaged electron density across the star-forming disks at four different redshifts, yielding unique constraints on the volume filling factor of ionized gas in HII regions across 10 Gyr of cosmic history. We measure the relationships between electron density and global galaxy properties, and compare these measurements with predicted functional forms to evaluate whether the electron density evolution is most likely to be driven by changes in the strength of stellar feedback, the molecular cloud density, and/or the hydrostatic equilibrium pressure.

The characteristic mass of stars is closely linked to the thermodynamic behaviour of interstellar gas, which controls how gas fragments as it collapses under gravity. As the Universe has grown in metal abundance over cosmic time, this thermodynamic behaviour has evolved from a primordial regime dominated by competition between compressional heating and molecular hydrogen cooling to a modern regime where the dominant process in dense gas is collisional coupling between gas and dust, with the dust temperature set by a competition between stellar feedback and radiative cooling. However, the transition between these regimes — in particular the role of stellar feedback and dust-gas coupling at low- to intermediate-metallicity — has received limited exploration. In this paper we map out the primordial-to-modern transition by constructing a series of simple models for the thermodynamics of collapsing, dusty gas clouds at a range of metallicities, including a wide range of physical processes: H₂ cooling, atomic and molecular line cooling, compressional and cosmic ray heating, heating of dust by stellar feedback, radiative cooling of dust, and collisional coupling between dust and gas. We use these models to identify the dominant thermodynamic processes, and the characteristic stellar masses they impose, as a function of metallicity. We show the transition from the primordial regime to the modern regime begins at metallicity Z ~ 10^-3 Z_⊙, where Z_⊙ is Solar metallicity, passes through an intermediate stage where metal line cooling is dominant at Z ~ 10^-2.5 Z_⊙, and then transitions to the modern dust-dominated regime at Z ~ 10^-2 Z_⊙. This transition is accompanied by a dramatic change in the characteristic stellar mass, from ~ 10 M_⊙ in the low-metallicity regime to ~ 0.3 M_⊙ once dust coupling begins to dominate, which marks the appearance of the modern bottom-heavy stellar initial mass function.

The lifecycle of stars is well understood, with gas cooling, collapsing under its own weight to form stars, then these stars driving away their natal clouds through radiation and winds, till their own deaths inject energy and metals into the gas to begin the cycle again. However the timescales of cooling, collapsing and clearing are not well understood. Here I will detail multiwavelength observations of nearby galaxies from the PHANGS survey, capturing the cool gas, the birth of stars and their eventual cleared clusters, so that we can trace the timescale of star formation, and how the winds clear theirs surrounds before their eventual deaths.

Understanding the build-up of stellar mass is one of the primary goals of extra-galactic astronomy. Various theoretical and observational studies find that star formation activity for galaxies in high density region peaks between redshift z=3-5, whereas for galaxies in the low density environment it peaks between redshift z=1-2. I will present the first measurements of star formation histories of galaxies in a proto-cluster at z~2 using SED fitting code Prospector. I will demonstrate that environment affects the stellar mass build-up in massive galaxies and show early signs of star formation suppression. I will also present a comparison of star formation histories from IllustrisTNG cosmological simulations and using IllustrisTNG, show how that the nature of environment of the galaxy itself pushes the massive galaxies towards their end (quenching).

Since the first observation of gravitational waves from a binary black hole merger in September 2015, ~50 additional binary black hole mergers have been identified in data from the Advanced LIGO/Virgo interferometers. These observations give us a powerful probe of the distribution of the masses, spins, and locations of merging astrophysical black holes. In this talk, I will discuss how we are able to use these observations to learn about the formation history of these cosmic corpses and ultimately uncover the mechanisms of stellar explosion and binary formation and what we have learned so far.

Fast Radio Bursts are millisecond-duration bursts of radio waves. First detected at Parkes in 2007, they have been a source of intense speculation, scrutiny and delight for teams of astronomers around the world. Under the auspices of the CRAFT survey science project, we have used Australian Square Kilometer Array (ASKAP) to not only detect tens of new FRBs but, for the first time, obtain sub-arcsecond positions for once-off FRBs enabling their position within host galaxies to be identified. Some of the results from the project include the discovery of dispersion-measure fluence relation for FRBs, the fact that FRBs come from a wide range of galaxy types, the low unexpectedly low density and magnetisation of an intervening galaxy halo, and the discovery of 50% of the baryons in the universe. I will also describe the Upgrade we are currently building, that will increase the discovery rate by at least a factor of 5, and process data at a rate of 40 trillion pixels per second.

Astronomy offers a fresh angle to engage the public with the science of climate change. Astronomers bring an understanding of the underlying cause-and-effect physics governing planetary behaviour from the widest perspective of all: the origins, evolution and fate of the solar system itself. The energy budget of Earth, the fate of our neighbouring worlds in the solar system, and the emerging results from exoplanetary discovery can be woven into a compelling narrative. This talk asks you to join us in bringing evidence-based reason, drawn from your own field, to the forefront of public discourse.

In this session we will present a short overview of services ADACS provides to the Australian astronomy community. This is followed by a project showcase highlighting how we have supported projects over the past 4 years with examples ranging from HPC to web solutions and accommodation of large and growing projects under the ADACS merit allocation program.

The Square Kilometre Array (SKA) is poised to usher in the next era of astronomical discovery and advanced data processing. The Australian SKA Regional Centre (AusSRC) will be Australia’s part of a global computing and data delivery network that will enable ground-breaking science by providing the connection between the telescopes and the science community. Recently, the Australian Government announced $387.1 million of new funding to meet Australia’s commitments as co-host of the SKA Observatory. A portion of that investment ($63 million) will be used to establish and build up the capability of the AusSRC. I will be giving a brief overview of the goals of the AusSRC, its current effort to support SKA precursor science projects, and how we will be working with the Australian SKA community to effectively deliver SKA data products and the required analysis tools to scientific users.

In this talk I present my learnings from developing Birli, a pre-processing library for the Murchison Widefield Array’s new MWAX correlator I have been developing as part of the Australian SKA Regional Centre design study. If you have never had a painful experience developing Astronomy software, and you are happy with your code’s performance, then you are clearly doing things right and have no need to attend. However, if your experience of software development has been less than ideal, I would like to share with you a few different methodologies and tools which have personally saved me days of pain. I will explain the advantages of continuous integration, agile, test-driven development, and benchmark automation, while trying not to evangelize too much about the Rust programming language.

Post-processing of large radio astronomical data, such as ASKAP surveys, can be a complex process involving a distributed science team working across various data centres; the datasets are large, the pipelines are often requiring heterogeneous systems to run on, the codes are often unoptimized, the processing often lacking provenance, and getting through post-processing for large surveys is currently mostly manual and labour intensive. Thus, post-processing shifts the overall effort from the science itself to the logistics of post-processing. WALLABY is an ASKAP HI survey, the post-processing for which involves mosaicking of spectral-line data-cubes, source finding, cross-matching, computing moment maps for the detected galaxies, and other smaller steps in manipulations and interactions with the data. We have developed a new post-processing framework to streamline WALLABY post-processing. This system includes interactive computing notebooks, databases, web portals and container-driven computational pipeline tools that collectively abstract low-level computing details. We will report on how this new framework is helping the science team to do science with ASKAP spectral-line data.

Astronomy is being transformed by massive stellar spectroscopic surveys, such as RAVE, APOGEE and GALAH. The next generation of surveys — including WEAVE, 4MOST and SDSS V’s MWM — will expand the available spectroscopic data well into the millions of stars. How are we to efficiently sift through these huge datasets to reliably identify rare and interesting stars? Extremely Metal-Poor (EMP) stars are an example of such interesting stellar objects, as they provide a window into the history of the early Universe. EMP stars yield critical information for many disciplines within Astronomy, ranging from supernova physics to early galaxy formation and the epoch of reionisation, yet their relative rarity constrains our ability to probe those early times. As a case study, I present a methodology incorporating machine learning to target EMP stars within the GALAH survey, with exciting results: the identification of 12 candidates with Fe/H < -3.5, which is ~5% of the known population. Such techniques can be adapted to find other rare classes of objects in large spectroscopic databases.

The standard model of cosmology, ΛCDM, has established itself as a robust and accurate way of describing the universe. However, a few questions remain open, such as: what is the nature of dark matter, what are the masses of neutrinos, and what is the origin of the difference between high- and low-reshift measures of the expansion rate? In this talk, I will pursue these topics by presenting constraints on the ΛCDM model and various extensions from SPT-3G 2018 EE/TE, the latest cosmic microwave backgorund dataset by the South Pole Telescope collaboration. I test for deviations from the standard model using SPT-3G data alone and in combination with Planck and baryon acoustic oscillation measurements. Finally, I explore constraints on the expansion rate and avenues to reconcile the Hubble tension. Using the new information of the SPT-3G 2018 dataset, I present the tightest constraint on the Hubble constant from CMB power spectra to-date, and compare it to low-redshift measurements of the expansion rate.

Direct measurements of galaxy peculiar velocities (PVs) offer a unique way to probe the hidden mass and motions in our local Universe, and test different cosmological models and theories of gravity. In this talk I will introduce our new ‘SDSS Peculiar Velocity’ catalogue, ~30,000 unique peculiar velocities measured using the Fundamental Plane of galaxies. This 7,000 deg^2 homogeneous sample comprises the largest set of peculiar velocities produced to date, extends the reach of PV surveys up to a redshift limit of z=0.1, and complements the existing 6dFGSv peculiar velocity dataset. I’ll discuss some of the challenges we found in recovering accurate peculiar velocities at large cosmological distances and with larger numbers of objects than ever before, and the methodological improvements these led too. I’ll then finish with some forecasts for what can be done with the new SDSS PV catalogue on it’s own and in combination with existing data, and how we intend to push this even further with data from upcoming spectroscopic surveys such as DESI.

Searching for space-time variations of the constants of Nature is a promising way to search for new physics beyond General Relativity and the standard model motivated by unification theories and models of dark matter and dark energy. We propose a new way to search for a variation of the fine-structure constant using measurements of late-type evolved giant stars from the S-star cluster orbiting the supermassive black hole in our Galactic Centre. A measurement of the difference between distinct absorption lines (with different sensitivity to the fine structure constant) from a star leads to a direct estimate of a variation of the fine structure constant between the star’s location and Earth. Using spectroscopic measurements of 5 stars, we obtain a constraint on the relative variation of the fine structure constant below 1e-5. This is the first time a varying constant of Nature is searched for around a black hole and in a high gravitational potential. This analysis shows new ways the monitoring of stars in the Galactic Centre can be used to probe fundamental physics.

Type Ia supernovae (SNe Ia) are important cosmological probes for measuring distances in the Universe. There is a need to better understand what drives the intrinsic scatter after SN Ia light curve corrections and the impact of environmental factors. SNe Ia in high mass galaxies appear more luminous after corrections compared with SNe Ia in low mass galaxies. We utilize SNe Ia host galaxies identified by the Dark Energy Survey (DES) in the five year photometrically confirmed sample, which have been targeted by the Australian Dark Energy Survey (OzDES) to obtain a spectrum and redshift for each galaxy. We provide a spectral study by first stacking the OzDES hosts by SN Ia Hubble residual and then utilize full spectrum fitting techniques to extract galaxy parameters (stellar population age, metallicity, mass-to-light ratio and emission line fluxes) and probe any environmental dependence. We find weak correlations with Hubble residual and the stellar populations of the spectra, compared with the stellar mass trend derived from photometry. Interestingly we see a strong trend with positive (fainter) SNe after light curve corrections residing in galaxies more affected by dust compared with the negative (brighter) SNe. This suggests the significance of incorporating reddening due to dust into current and future SN Ia light curve fitting models to reduce intrinsic scatter and improve their use in cosmological analysis.

Type Ia supernovae (SNe Ia) have secured their place as important cosmological probes, with upcoming surveys (such as the Legacy Survey of Space and Time on the Vera C. Rubin Observatory) observing hundreds of thousands of SNe Ia candidates. Currently, theoretical models are unable to model SN Ia spectra with sufficient fidelity, so empirical light-curve models based on observed SN Ia data are crucial for extracting accurate distances. I present an updated version of the popular SNe Ia model, SALT2, and show how it can be used to improve supernova cosmology results. I also discuss imminent model developments, including an Australian-based observation program to provide quality model training spectra. These developments will ensure that a SN Ia model is capable of meeting the needs of large-scale photometric surveys like LSST in the future.

Ambitious Galactic spectroscopic surveys such as Gaia-ESO, APOGEE, and GALAH have obtained high-resolution, high signal-to-noise ratio spectra of hundreds of thousands of stars, spanning large swaths of the Milky Way. The high-resolution surveys provide detailed chemical fingerprints for each program star, typically measuring 15-30 elements per star. A key question to these surveys is how many of these elements actually contain independent information. It has long been recognized that the ratio of alpha-elements to iron peak elements is an important dimension of stellar abundance variation in addition to overall metallicity. However, the evidence on variations beyond the metallicity and alpha-enhancement is mixed. Some studies of stars’ multi-element abundance distributions suggest at least 5-7 significant dimensions, but others show that many elemental abundances can be predicted to high accuracy from [Fe/H] and [Mg/Fe] (or [Fe/H] and age) alone. In this talk, I will reconcile these seemingly contradictory results. I will show that both propositions can be, and are, simultaneously true. In particular, I will discuss, although one could infer elemental abundances to high accuracy with only [Fe/H] and [Alpha/Fe] elements, residual abundances can display clear correlations between other elements, which signal cannot be explained by only two elements. I will demonstrate that cross-element correlations are a much more sensitive probe of hidden structure than dispersion, and they can be measured precisely in a large sample even if star-by-star measurement noise is comparable to the intrinsic scatter. In short, many elements have an independent story to tell, even for the “mundane” disk stars and elements produced by core-collapse and Type Ia supernovae. The only way to learn these lessons is to measure the abundances directly, and not merely infer them.

Galaxies evolve due to the interplay of internal and external physical processes. Understanding their connections with global properties and gas and star kinematics can provide further insights in the complex physics of galaxy evolution. We use the EAGLE hydrodynamical simulation to study the evolution of gas kinematics for a wide range of galaxy properties and environments. We aim to connect this evolution with relevant physical processes such as stellar feedback, gravitational instabilities and mergers. In particular, we analyse the evolution of the gas velocity dispersion as a function of physical quantities that attempt to trace these processes. Our results indicate that stellar feedback has a significant impact on increasing the gas velocity dispersion and that gravitational instabilities are the most important drivers for turbulence at high redshifts.

Historical theory assumed that gas and dark matter (DM) had identical angular momentum (AM) within haloes. However, hydrodynamical simulations have challenged this assumption – they find that AM of gas is larger than that of DM. Internal factors (e.g. AM transformation) and external factors (e.g. merger) can rearrange the orbits and change the AM. This project aims to find the physical mechanims which drive the enhancement of AM of gas to DM. We select ~50000 haloes at z=0 in the non-radiative hydrodynamical simulation SURFS and analyse the AM evolution of haloes. We find that the spin parameter of gas increases through the cosmic time while the spin parameter of DM remains constant. We also analyse the self-misalignment of gas and DM within haloes and find that statistically, DM has more self-misalignment than gas, which descreases the AM amount of DM. Finally, we set up control simulations to investigate the internal factors who may drive the AM exchange between gas and DM within haloes. We find that the asymmetric shapes of haloes can form torques inside during the evolutions, thus a part of the AM of DM transfers to gas and enhance the AM of gas.

The formation of S0 galaxies is still an open question in modern astrophysics. I will present my PhD work that explores the formation of S0 galaxies in SAMI galaxy clusters. I will show a new method to study the stellar populations of bulges and disks separately, which combines 2D photometric bulge/disk decomposition with spatially-resolved spectroscopic data. Studying colours, I find that the formation of S0 galaxies is primarily driven by processes acting in the cluster core on the disks. Breaking the age-metallicity degeneracy, I conclude that the redder colour in bulges is due to their enhanced metallicity relative to the disks instead of differences in age.

Massive stars play a critical role in the evolution of galaxies and star clusters. Recent observations of the latter have highlighted the need for systematic studies dedicated to probing the impact of massive stellar evolution on the properties of stellar populations. In this talk, I will present results from a rapid single stellar evolution code which uses interpolation between sets of pre-computed stellar tracks to evolve populations of stars. Using interpolation on the data from different stellar evolution codes, I will show how different physical ingredients used in the evolution of stars, such as the treatment of radiation dominated envelopes of massive stars, can lead to significant differences in their evolutionary properties. I will discuss the implications of these differences on the evolution and interaction of stars in binaries, and how it can impact compact binary mergers and the predictions of gravitational wave events.

High precision astrometry has entered a Golden Age, ushered in by the Gaia mission and surely culminating in the clearest 3D picture of the Milky Way to-date. The Gaia satellite has been revolutionary in many ways and yet, as a relatively small telescope, it is fundamentally limited in its study of both faint and crowded sources. Adaptive optics allows ground-based telescopes to operate at or near their diffraction-limit, overcoming seeing limitations and surpassing space-based telescopes purely by virtue of their size. The Multi-conjugate Adaptive-optics Visible Imager-Spectrograph (MAVIS) is an instrument being designed for the Very Large Telescope Adaptive Optics Facility. Equipped with MAVIS, the VLT will be the only 8m-class telescope, ground-based or otherwise, to operate at its diffraction limit (0.02 arcseconds) in the optical (550 nm). Designed with astrometry in mind, MAVIS must deliver precision astrometry at the 150 micro-arcsecond level, with a goal of 50 micro-arcseconds, the same requirement as the 39m Extremely Large Telescope. To verify this requirement will be met, we have created the MAVIS Image Simulator (MAVISIM), an image simulating tool to explore MAVIS science cases ranging from stellar to extra-galactic science. MAVISIM accounts for three major errors introduced by adaptive optics, including PSF field variability, along with imager and detector characteristics. In this first test of MAVISIM, we have investigated both the astrometric capabilities of MAVIS and a key science case for the instrument, the presence of intermediate mass black holes (IMBHs) in globular clusters. In this talk I will present exciting initial results from MAVISIM showing that MAVIS will: i) meet its astrometric requirements and ii) be able to detect the kinematic signature of a central 1500 solar mass IMBH in the crowded central region of NGC 3201.

I use idealized simulations of equilibrium stellar disks embedded within spherical dark matter halos to show that spurious collisional heating leads to a systematic increase in the velocity dispersion of disk stars, and to an artificial increase in disk thickness and size. This is a result of collisional relaxation and is driven primarily by the coarse-grained nature of simulated dark matter haloes, with little impact from bulges, stellar haloes and disk stars. The effects are determined primarily by the mass of simulated dark matter particles (or equivalently by the number of particles at fixed halo mass), their local density and characteristic velocity, but are largely insensitive to the masses of stellar particles. This suggests that the effects of numerical relaxation on simulated galaxies can be reduced by increasing the mass resolution of the dark matter in cosmological simulations, with limited benefits from increasing the baryonic (or stellar) mass resolution. I provide a simple empirical model that accurately captures the effects of collisional heating on the vertical and radial velocity dispersions of disk stars, as well as on their scale heights; I use the model to assess the extent to which spurious collisional relaxation may have affected the structure of simulated galaxy disks.

MINERVA-Australis at the University of Southern Queensland’s Mount Kent Observatory is the only southern hemisphere precise radial velocity facility wholly dedicated to follow-up of TESS planets. MINERVA-Australis is a partnership between MIT, UNSW Sydney, George Mason University, University of Louisville, Nanjing University, UC-Riverside, University of Texas, and the University of Florida. Observing time is also available to the US community via NSF NOIRLab proposal calls. Being fully robotic, we have been unaffected by Covid-19 closures. We have contributed data to the validation of 23 TESS planets. I give an overview and update of operations, highlighting our recent mass measurements for TOI-778 and TOI-1842. I also describe our new photometric capabilities, aiming to validate small TESS planets and to rescue planets from ephemeris erosion.

Ultra-short-period planets might have catastrophic fates due to strong tidal interactions with their host star. To better understand when these events occur, their tidal evolution and interchange of orbital angular momentum must be modeled. However, this poses a challenge as the amount of tidal friction depends on the dissipative properties of stellar and planetary interiors which are highly unconstrained for extrasolar systems. By coupling interior structural changes in the star and the planet resulting from the energy released per tidal cycle, we aim to simulate the orbital evolution of ultra-short-period planets and the spin-up produced on their host star, exploring the importance of including the time-varying structure of the bodies into the inwards migration of orbiting planets. For the first time, we allow the strength of magnetic braking to vary within a tidal model that includes photo-evaporation, drag caused by the stellar wind, stellar mass loss, and stellar wind enhancement due to the in-falling planet. We then use this model to calculate the evolution of the orbital elements of the two exoplanets with the shortest periods known to date, NGTS-10b and WASP-19b. Contrary to previous work, with variations in transit times of ~30 – 190 seconds over 10 years, our model shows that such changes would be 90% smaller. In addition, we found a method that uses the shrinking rate of the planetary orbit to get some insight into the tidal dissipation of the system. This work suggests that ultra-short-period planets will undergo orbital decay in time-scales that depend on the evolution of the internal structure of the star, as well as the contribution of the stellar envelope to the transfer of angular momentum. Our findings imply that observational verifying of orbital decay, using present and future campaigns, will be significantly more challenging.

After almost three decades of exoplanet discoveries, the way short-orbit (less than a few weeks) gas giants (a.k.a. Hot Jupiters, or HJs) come to exist is still puzzling the community. Orbit obliquity, i.e. the angle between the stellar rotation axis and the orbital normal of the planet, can reveal misaligned orbits, imprints of potentially violent dynamic interaction in a HJ early life. However, the orbital obliquity angle of planets can change over billions of years of tidal evolution, muddying the population and preventing us from disentangling the true primordial orbits from which hot Jupiter originated. HIP 67522 is a 17 Million year old Solar analog that hosts two transiting planets. In particular, HIP 67522b is a close-in hot Jupiter with an orbital period of 6.95 days and a radius of 10.02 R⊕. In this talk, we present our exciting results on the obliquity of HIP 67522b, the last piece of the puzzle for this orbiting planet that will deliver crucial insights on the formation history of the commonly found yet mysterious HJs. We will discuss our obliquity measurement from a series of spectroscopic transits gathered over the last year, and our modelling of the stellar activities that dominate the signals from this young star.

We still do not understand how planets form, or why extra-solar planetary systems are so different from our own solar system. Recent observations of protoplanetary discs have revealed rings and gaps, spirals and asymmetries. These features have been interpreted as signatures of newborn protoplanets, but the exact origin is unknown, and remained until recently poorly constrained by direct observation. In this talk, I will show how high spatial and spectral resolution ALMA observations can be used to detect the kinematic signatures of embedded planet in their discs, and discuss the implications on our understanding of planet formation.

The early evolution of a star is intertwined with that of its planets and protoplanetary disk. Recent results reveal that some stellar chemical peculiarities arise from separation of dust from gas in planet-forming disks. Thus stellar composition build-up is linked to planet formation and disk evolution, but many aspects of this remain unclear. Disk evolution is thought to be rapid (3—5 Myr timescales), but age estimates have previously relied upon the ages of stellar associations, which can be unreliable because of age dispersion within associations and episodic accretion. Hence, the ages and intrinsic metallicities of protoplanetary disks are rarely known precisely. I will discuss recent results for the pre-main-sequence star HD139614, where we use stellar pulsations to determine an age to better than 10% precision. I will describe the evolution of pulsation frequencies in pre-main-sequence stars and how this allows masses and metallicities to be determined in a degeneracy-free way, permitting stellar associations to be dated with much better precision. Finally, I will explain how a planet-forming disk has resulted in this star being chemically peculiar.

Radio emission from M-dwarfs is an important probe into their stellar atmospheres and magnetic fields, and gives insights into the potential habitability of exoplanets found orbiting them. To date however, most of our understanding of radio emission from these systems have been from targeted observations of M-dwarfs with known magnetic activity, leaving it unclear if these are representative of the population as a whole. In this talk I will present results from our volume-limited survey of M-dwarfs as part of the Rapid ASKAP Continuum Survey (RACS), which covers the Southern sky below a declination of +41 deg at a frequency of 888~MHz. We crossmatched the RACS catalogue with stars in the Gaia DR2 catalogue within 200~pc. We identified 21 radio-loud M-dwarfs, with 12 having no previously reported radio emission. Four of the radio-loud M-dwarfs had no circularly polarised counterpart in RACS, with the remaining 17 demonstrating highly circularly polarised emission. We investigate the nature of the detected radio emission including using follow-up observations from phase one of the Variable and Slow Transients Pilot survey (VAST) and the Australia Telescope Compact Array (ATCA). We discuss the implications of our findings for future radio surveys, in particular the full VAST survey.

The Galactic ASKAP (GASKAP) HI survey is now underway and producing stunning, new observations of HI in our Galaxy and the Magellanic System. Studying the most local neutral atomic gas allows us to understand the details of the processes that drive galaxy evolution and provide critical tests of existing theoretical models and simulations. I will present a status update on behalf of the GASKAP-HI team and highlight the active science areas we are investigating with our Pilot data, including: filaments, turbulence, line decomposition and kinematic structure, absorption measurements, and comparisons with other phases of the ISM and magnetic fields.

The Galactic ASKAP (GASKAP) project is opening a new window on cold (40 – 200K) neutral hydrogen in the local universe. We are, for the first time, taking an unbiased sample of absorption by this cold gas across large fields of view. This allows us to map out the cold gas across both our nearest neighbours as well as our own Galaxy. I will present this new view we are seeing of cold HI in both the Small Magellanic Cloud and the Galactic Plane towards the bar.

The inflow of cosmological gas onto haloes and galaxies, while challenging to directly observe and quantify, plays a fundamental role in the setting their observable properties over cosmic time. I will present several new results from my current work, which explores net gas accretion rates to central and satellite galaxies in the EAGLE hydrodynamical simulations. At z=0, we find that at least half of all central galaxies are net accreting gas, compared to only 20-30% of satellite galaxies below 10^11 Msun – dropping close to 0% for satellites in massive (>10^14Msun) haloes. If we control for the mass of a galaxy relative to its halo, we find that centrals and satellites actually exhibit similar inflow rates for the small overlap in their stellar-halo mass ratio. Our work, which accounts for the combined effect of gas accretion and outflows, quantifies how environment influences the baryon cycle of galaxies in a cosmological context.

In this talk, I will discuss two interesting results from our searches for GRB radio afterglows using unbiased wide-field ASKAP surveys. (1) We detected the radio afterglow of low-luminosity GRB 171205A approximately 511 days post-burst in a targeted search through the Rapid ASKAP Continuum Survey (RACS) and the ASKAP Survey for Variables and Slow Transients (VAST). This was the first confirmed detection of a GRB afterglow in an unbiased wide-field radio survey (Leung et al. 2021; MNRAS, 503, 2). Follow-up radio observations with the Australia Telescope Compact Array along with archival radio data revealed clear signatures of a wind-like circumburst medium and typical microphysical burst parameters consistent with the wider population of GRBs. (2) We identified a candidate dark burst radio afterglow associated with GRB 150428A in a subsequent commensal search in ASKAP archives and conducted further radio observations to characterise this candidate. As telescope time allocation is limited, dark bursts (GRBs with dust-suppressed optical counterparts) are often not prioritised in traditional radio follow-up campaigns, making it difficult for the microphysical parameters and energetics of these bursts to be constrained – our work demonstrates that wide-field surveys could be a useful, complementary alternative for bursts where traditional follow-up is unlikely or difficult. Lastly, we will also discuss our techniques for ongoing searches in VAST data for off-axis GRB afterglows without a high-energy counterpart, or “orphan afterglows”, which will allow us to constrain the true GRB population rate and their jet geometry.

The Epoch of Reionisation (EoR) is the period within which the neutral universe transitioned to an ionised one. This period remains unobserved using low-frequency radio interferometers which target the 21 cm signal of neutral hydrogen emitted in this era. The Murchison Widefield Array (MWA) radio telescope was built with the detection of this signal as one of its major science goals. One of the most significant challenges towards a successful detection is that of calibration, especially in the presence of the Earth’s ionosphere. By introducing refractive source shifts, distorting source shapes and scintillating flux densities, the ionosphere is a major nuisance in low-frequency radio astronomy. We introduce SIVIO, a software tool developed for simulating observations of the MWA through different ionospheric conditions estimated using thin screen approximation models and propagated into the visibilities. This enables us to directly assess the impact of the ionosphere on observed EoR data and the resulting power spectra. We show that the simulated data captures the dispersive behaviour of ionospheric effects. We then investigate the effects of different ionospheric turbulence levels and spatial structure on the 21 cm power spectrum both in simulations and observed MWA data, as well as, improved methods in MWA ionospheric calibration. In turn, this will inform on the best strategies of identifying and efficiently eliminating ionospheric contamination in EoR data moving into the Square Kilometre Array era.

Clusters of galaxies provide ideal physical laboratories for studying a wide range of physical processes associated with hot gas (thermal components) and magnetic fields (non-thermal components). However, studying cluster magnetic fields in detail is difficult, due to the wide variety of physical processes undergone by clusters during their lifetime. Diffuse radio sources (such as the canonical relics and haloes) and tailed radio galaxies (which are frequently found in clusters) can provide key signposts to these physical processes, and thus help us understand the magnetic field topography. Abell 3266 is a rich, Southern cluster undergoing a particularly complex merger event, and as such provides a golden opportunity to study the thermal and non-thermal properties of the intracluster medium (ICM) on a broad variety of scales. In this talk, I will present the results of new, deep radio observations performed with the Australia Telescope Compact Array (ATCA) and Australian Square Kilometre Array Pathfinder (ASKAP). These observations reveal a plethora of previously-unseen diffuse, steep-spectrum radio sources associated with the ICM; additionally, we detect a multitude of active and remnant radio galaxies that are now resolved in unprecedented detail. Using our exquisite new radio data in conjunction with X-ray observations from XMM-Newton and eROSITA, I will discuss the properties of these newly-discovered sources, and what we can learn from them — both about their nature and the dynamical history of Abell 3266 — as well as what this means for upcoming cluster surveys with ASKAP.

The Advanced LIGO and Virgo detectors have now reported dozens of detections of gravitational waves from compact binary systems. As we observe more of the gravitational-wave universe, we may detect signals from novel sources, for example core-collapse supernovae or the remnant of a binary neutron star merger. Some of these sources are not well modeled, and therefore it is important to be able to confidently detect and characterize gravitational waves with minimal assumptions about the signal morphology. One method to recover generic signals is the BayesWave algorithm which uses a reversible-jump Markov chain Monte Carlo to reconstruct transient events in detector data as a sum of sine-Gaussian wavelets or chirplets. In this talk, we will give an overview of BayesWave, then introduce improvements made to the algorithm and its applications in the era of gravitational-wave detection.

Gravitational Waves (GW) are ripples in space-time created by the collision and merger of heavy, compact objects like black holes and neutron stars. The co-incident detection of GWs and a short gamma-ray burst in 2017 has started a new era in multi-messenger astronomy and has provided us deep insight into the abundances and rates of mergers of GW sources in the universe. In order to have more co-incident detections, these sources need to be localized with very high accuracy and with much greater speed than what currently used Bayesian inference techniques afford. In this talk, I am going to describe how deep learning models can be used to localize GW sources orders of magnitude faster, with comparable accuracy to optimal Bayesian algorithms. In particular, I am going to describe two deep learning models, optimized for two specific tasks: a denoising autoencoder for extracting pure GW waveforms from noise and an encoder-decoder network that uses the pure waveforms for accurate localization of the GW sources.

Since their first detection in 2015, LIGO and Virgo have reported more than 50 gravitational-wave signals. These space-time ripples come from coalescing compact binaries, which spiral around each other before they plunge together and merge. The paths that these objects trace around each other in the fragments of seconds before they merge can contain a wealth of information about the previous lives of these objects. Binary compact objects have two overarching formation channels: isolated, in which the pair live from birth to death as a binary without any external influence, and dynamical, in which two compact objects become bound in a populous environment like a star cluster. Isolated binaries are expected to trace circular paths around each other close to merger. However, when binaries form dynamically, their paths can be elliptical. This orbital eccentricity can be inferred from the gravitational-wave signal of the binary. In this talk, I present constraints on eccentricity obtained for binary black hole and neutron star coalescences detected by Advanced LIGO and Virgo, including ‘monster’ binary black hole GW190521. I showcase related work that uses binary properties like eccentricity to distinguish first-generation from multi-generational mergers. I show how future detectors will be able to use similar methods to trace the evolution of globular clusters in the Universe. Finally, I show how the orbital eccentricity of a single binary can have implications for every binary so far detected by LIGO and Virgo.

A number of high energy satellites have been proposed to coincide with the A+ gravitational wave (GW) observation run with the key goal of probing gamma-ray bursts (GRBs) through joint GW-GRB observations. Calculating the expected joint gravitational wave – gamma ray burst detection rates is an important part of the design studies for these instruments. I will present two complementary NASA GRB missions, StarBurst and MoonBeam, set for operation during the A+ era. I will discuss the framework used to calculate joint rates in the design studies for these instruments over a range of GW networks and gamma-ray sensitivities. I will present joint inference of the gamma-ray burst jet structure, rate evolution and luminosity function of the sources and show how this is an important component in predicting joint event rates.

Pulsar glitches are sudden increases in spin frequency that occur against a background of steady spin down. Recent observations from the NICER instrument on the International Space Station have detected several ‘anti-glitches’, sudden decreases in spin frequency, in the accreting pulsar NGC 300 ULX-1. While several anti-glitches have been observed in magnetars, this is the first case where the pulsar is spinning up, suggesting a direct analogue of glitches in decelerating pulsars. I present the results of simulations that demonstrate that glitches and anti-glitches can be caused by superfluid vortex avalanches, and compare the properties of glitch and anti-glitch size and waiting time probability distributions.

I will present a world-first simulation of the tidal disruption of a 1Msun star on a parabolic orbit by a million solar mass black hole, following the disruption and subsequent long-timescale fallback of material for up to one year post-disruption, performed in full General Relativity in the Kerr metric. I will demonstrate the formation of an eccentric accretion disc from stream-stream collisions and the powering of an optically thick, super-Eddington outflow. I will show several decades-old mysteries regarding tidal disruption events (TDEs) can be understood in the light of our simulation results, including why observed TDE seem to emit in the optical/UV rather than X-ray band.

In this workshop we will provide a broad view on commercialisation across Australian astronomy, before introducing some examples of commercialisation in action and then opening the session for Q and A. This workshop is to be the first step in the development of an astronomy commercialisation community aimed at reducing the barriers to astronomers and departments wanting to follow this route.

We study the assembly history of a sample of nine selected lenticular (S0) galaxies from their large radii kinematics that extend out to ~6 effective radii (Re) by combining the kinematics of the stars, globular cluster (GC) and planetary nebulae (PNe) tracers. We find that six galaxies show good kinematic alignment of the GC and PNe tracers with respect to the underlying stars in the overlapping radii (i.e. within ~2-3 Re), therefore suggesting that both GCs and PNe are good tracers of the underlying stellar population beyond that traced by the stars. On the other hand, the remaining three galaxies show kinematic twists and misalignment of both the GC and PNe tracers with respect to the underlying stars, therefore suggesting recent galaxy interactions and mergers. From the comparison with simulations, extending out to similar galactocentric radii (i.e. ~5 Re), we suggest that all six aligned galaxies that show similar dispersion-dominated kinematics at large radii (i.e. >2-3 Re) had similar late (z<1) assembly histories characterised by mini mergers (mass-ratio<1:10). The different Vrot/σ profiles of the inner regions are then the result of an early (z>1) gas-rich minor merger (1:101:4) merger that spun-up the rotation of both the red and blue GC sub-populations at large radii. Overall, we find that the formation histories of S0 galaxies in low-density environments can be quite complex with merger events playing a crucial role in shaping the observed distinct Vrot/σ profiles of the different kinematic tracers (i.e. stars, GCs and PNe) in our galaxies out to large radii, depending mainly on their time of occurrence, specific orbital configuration and mass-ratio.

Simulations of early-type galaxies through cosmic time indicate the average density slope of early-type galaxies was as steep as -3 at redshifts of ~2, and approaches the `isothermal’ slope of -2 in the local Universe via dry mergers, which agrees with local Universe dynamical modelling results. However, at intermediate redshifts (0.3 < z < 1), gravitational lensing measurements of density profiles show the opposite evolution. In this talk I will present the results of flexible Jeans Anisotropic MGE (JAM) modelling of 90 early-type galaxies in the HST Frontier Fields sample in the redshift range 0.3 < z < 0.54. Dynamical models were built using MUSE 2D stellar kinematics combined with HST photometry, with the same methods as local Universe studies. The results indicate no evolution in the density slope in the past 4-6 Gyrs of cosmic time, which supports a dry merger model and is at tension with lensing results. These results will be tested with high-quality data from the new MAGPI survey, which will allow us to examine potential environmental effects in the near future.

We use the SAMI galaxy survey to study the relationship between stellar metallicity and gravitational potential in 1902 nearby galaxies. We build on previous work to show that all galaxies, regardless of star-formation rate, lie on a single relation between their central metallicity( [Z/H]) and their gravitational potential (~M/r). We then build a toy model to explain our results, finding that the mass-metallicity, potential-metallicity and mass-size plans can be recovered in a model where galaxies quench nearly instantaneously. This is in contrast to previous work which showed that the quenching of galaxies must be slow to recover the mass-metallicity relation, and highlights the importance of measuring the size of galaxies (as well as their stellar mass) when studying their evolutionary paths.

The “HI KOALA IFS Dwarf galaxy Survey” (Hi-KIDS) uses KOALA+AAOmega at the Anglo-Australian Telescope (AAT) to get good-quality IFS data of a sample of nearby dwarf and irregular galaxies for which we already have 21cm HI interferometric data, exploring a parameter space which is not studied by current IFS galaxy surveys. Hi-KIDS studies the global and local properties of the ionized gas (metallicity, SFR, kinematics) and the stellar component (star-formation history, kinematics) of these dwarf galaxies. It also compares the combined IFS+radio data with theoretical predictions of chemical evolution models to investigate the efficiency of the conversion of gas into stars. Hi-KIDS will provide a comprehensive picture of the physical processes ruling dwarf galaxies, the data will be released publicly in AAO’s Data Central as legacy. In this talk I will provide an update of the survey, including discussing the effort made in the developing of the PyKOALA code to process the KOALA data. I will also emphasise how Hi-KIDS is a nice example of a science case for exploring the resolved properties of nearby galaxies using BlueMUSE at the VLT in the near future.

Galaxy mergers play an important role in how galaxies evolve over time, however, extragalactic astronomers do not yet completely understand the process by which those mergers happen. The merger history of a galaxy is thought to be one of the major factors that determines the internal kinematic structures of galaxies, with galaxies having undergone more mergers predicted to show different properties. Therefore, we expect that the internal kinematic structures of passive galaxies could show different characteristics depending on their merging history. We apply Schwarzschild orbit-superposition models to passive galaxies in the SAMI Galaxy Survey in order to reconstruct their internal kinematic structure and mass distribution. We find that changes in the internal structures are mostly driven by stellar mass and we see intriguing signs of different orbital structures in galaxies with different kinematic signatures.

The growing number of Low Earth Orbit (LEO) objects has been an increasing concern for the Space Domain Awareness (SDA) community and the astronomy community. While the rapidly increasing number of satellites demands the development of a wide field-of-view SDA sensors that is capable of performing simultaneous detections, many recent studies have also highlighted the importance of understanding the near-earth environment for astronomy in optical, infrared, and radio wavelengths. Hence, we address these issues by using a low-frequency radio-interferometer, the Murchison Widefield Array (MWA), to perform space surveillance using passive radar techniques, whilst understanding its impact on FM band observations performed from the Murchison Radio-Observatory (home to the MWA and the future low-frequency Square Kilometer Array). In this talk, I will summarise the non-coherent passive radar capability developed using the MWA. We have developed and tested a LEO blind detection pipeline on archived MWA data, and we detect over 70 unique objects over multiple passes, demonstrating the MWA to be a valuable addition to the global SDA network. We detect LEO objects as small as 0.03 m2 radar cross-section and as far as ~1000 km. Additionally, we also detect FM reflections from Geminid meteors and aircrafts flying over the MWA. For many of the nearby detected objects, we split the MWA into two sub-arrays and perform line-of-sight range measurements using the parallax method. As part of this analysis, we show that the standard MWA RFI flagging strategy misses most of this RFI and that this should be a careful consideration for the SKA. We also demonstrate orbit determination and LEO catalog maintenance capability using the MWA, and the obtained orbital elements are in good agreement with the publicly released orbital elements by the Space Surveillance Network (SSN). Based on our understanding of the MWA SDA system, I conclude the talk by briefly describing the methods to mitigate the impact of FM reflecting LEO satellites on radio-astronomy observations, and how maintaining a catalog of FM reflecting LEO objects is in the best interest of both SDA and radio-astronomy.

The latest observing runs of Advanced LIGO/Virgo have brought dozens of new detections, ushering in the era of gravitational-wave catalogues. By studying populations of binary black hole (BBH) we are learning about the mass and spin distributions of black holes, allowing us to probe stellar evolution and binary formation mechanisms. In this talk, I describe the emerging picture of black hole mass and spin distributions from the population analysis of second LIGO-Virgo Gravitational-Wave Transient Catalogue (GWTC-2). First, we find that the primary mass spectrum contains structure beyond a power-law with a sharp high-mass cut-off. Second, we find that a fraction of BBH systems have component spins misaligned with the orbital angular momentum, giving rise to precession of the orbital plane. Moreover, 12% to 44% of BBH systems have spins tilted by more than 90 degrees, giving rise to a negative effective inspiral spin parameter. Third, we have updated merger rates for binary black holes and binary neutron stars. Additionally, we examine recent exceptional events in the context of our population models, finding that the asymmetric masses of GW190412 and the high component masses of GW190521 are consistent with our models, but the low secondary mass of GW190814 makes it an outlier.

In my talk, I will present the latest observed black hole-galaxy correlations, which have been found to have divisions depending on the host galaxy morphology. This work is based on the largest sample of local galaxies with dynamically measured central supermassive black hole (SMBH) masses. We measured the host galaxy properties using state-of-art two-dimensional isophotal modeling and the multi-component photometric-decomposition, incorporating the kinematic evidences for the presence of stellar disks. These decompositions allowed us to accurately estimate the galactic bulge/spheroid properties and reliably identify the galaxy morphologies. We investigated the black hole mass scaling relations for various sub-morphological classes of the galaxies, i.e., galaxies with and without a rotating stellar disk, early-type (E, ES, S0) versus late-type galaxies (all spirals), barred versus non-barred galaxies, and Sersic (gas-abundant accretion/wet merger) versus core-Sersic (depleted-core, dry merger) galaxies. Consequently, we have discovered significantly modified correlations of black hole mass with galaxy properties, e.g., the spheroid stellar mass, total galaxy stellar mass, central stellar velocity dispersion, bulge central light concentration (Sersic index), bulge size, and the projected and internal stellar mass density of the bulge. The final scaling relations are dependent on galaxy morphology, which is fundamentally linked with galaxy formation and evolutionary paths. These relations provide consistent predictions for the very recent directly-measured super massive and ultra massive black holes. The morphological dependence of black hole scaling relations poses ramifications for the virial factor and offers tests for simulations and theories for black hole-galaxy co-evolution. These scaling relations provide an easier way to estimate tidal disruption event rates, black hole merger time scales, morphology-aware black hole mass function, and improved characteristic strain model for the ground-based and space-based detection of long-wavelength gravitational waves generated by merging SMBHs.

The gravitational wave event GW190521 involves the merger of two black holes of ~ 85 M_⊙ and ~ 66 M_⊙ forming an intermediate-mass black hole (IMBH) of mass ~ 142 M_⊙. Both progenitors are challenging to explain within standard stellar evolution as they may belong to the upper black-hole mass gap. In this talk we propose a dynamical formation pathway for this IMBH based on multiple dynamical black hole mergers in the core of a dense star cluster. We investigate the simulated evolution of a specific merger chain involving seven individual mergers, attaining a final mass of ~ 97.8 M_⊙. We discuss the dynamical interactions that lead to the final IMBH product, and the evolution of the whole simulated black hole population. We also explore the effects of gravitational recoil on the viability of such a merger scenario. From the analysis, we estimate an event rate broadly consistent with the mean rate implied by GW19052, assuming that gravitational recoil ejection of progenitors has a low probability. We discuss implications for future gravitational wave detections of IMBHs, emphasising the importance of studying pathways for formation of BHs within the upper mass gap as a means to constrain such modelling.

Core-collapse supernovae (CCSNe) are a promising future multi-messenger source for gravitational wave detectors. In recent years, significant progress has been made in the modeling of regular neutrino-driven CCSN explosions. However, the gravitational wave emission from stronger hypernova explosions, powered by magnetic fields and rotation, have not been extensively modeled in three dimensions beyond the core bounce phase. Therefore, we investigate the impacts of rotation and magnetic fields on the explosion dynamics and gravitational wave emission of CCSNe in three dimensions. We simulate a 39 solar mass progenitor star with two different initial magnetic fields strengths up to 0.68s after the core bounce. We find our magnetorotational explosion models show differences in the time-frequency morphology of the post bounce gravitational wave emission in comparison to the neutrino-driven case. Our models have strong gravitational wave amplitudes that may be detectable out to ~4Mpc in a single Cosmic Explorer detector, and out to ~2Mpc by the Einstein Telescope.

Post-merger remnants from binary neutron star mergers are some of the most extreme forms of matter in the universe. With densities close to the limit where matter collapses into a black hole and temperatures exceeding 100GK. In coming years, gravitational waves offer the best method for directly observing these remnants. However, numerical-relativity simulations show that the structure of the gravitational waveform is complex. Here I show how we can model post-merger waveforms to allow the future detection of these remnants. We further show how well we can measure the time when a merger remnant collapses to a black hole for near-future gravitational-wave detectors.

We have performed 10 epochs of observations covering 90% of the localisation of GW190814, a possible NS-BH merger, with the Australian Square Kilometre Array Pathfinder spanning 2 to 655 days post-merger. While no radio counterpart has been detected to-date, this non-detection allows us to place tight constraints on the properties of GW190814. In this talk I will present the results of our observations as well as prospects for follow-up during future observing runs.

Globular cluster (GC) formation is one of the most intriguing puzzles in Galactic Archaeology. These relics from the high-redshift Universe are unique low-metalicity laboratories composed of two or more distinct stellar populations. Proposed explanations for the formation of multiple populations generally focus on processes independent of the GC’s environment. However, using original, self-consistent hydrodynamical simulations, I will discuss GC formation in the context of their parent galaxies. Our simulations produce a diverse range of clusters with characteristics consistent with observed GCs. We achieve this by altering the initial conditions of not only the GC progenitor but also its host dwarf galaxy. I will address the physical implications of our simulations, present scaling relations that align with current observations and relate these results back to our understanding of high-redshift dwarf galaxies.

It is known that the Galactic stellar halo holds crucial information for disentangling the mass assembly history of the Galaxy. The chemo-dynamical information encoded in halo stars enables the reconstruction of the Milky Way. Of particular importance are the halo populations of the inner Galaxy, as they likely retain pivotal information that may help decode early stages of the formation and mass assembly of the Milky Way, but however has so far been concealed due to the limitations in observing such regions due to high stellar density and dust extinction. In this talk, I will provide evidence for the discovery of a metal-poor structure located within the heart of the Galaxy that displays chemo-dynamic signatures of accreted populations. Characterised by a chemical composition resembling those of low mass satellite galaxies of the Milky Way, this structure appears to be chemically and dynamically detached from its more metal-rich counterparts in the inner Galaxy. We speculate this newly identified inner Galaxy structure (dubbed “Heracles”) is associated with an accretion event that occurred in the early life of the Milky Way, which constituted a major building block of the Milky Way halo, and played a major role in the formation of the Milky Way.

The luminous, massive Wolf-Rayet (WR) stars are thought to be immediate precursors to core-collapse supernovae. Despite the intrinsic rarity of stars in this ephemeral phase, understanding the physics of WR mass loss and evolution has broad ramifications for Galactic astronomy due to their intense winds and mass loss. WR stars can be found in binary systems where dust formation is wrapped into a spiral by the orbital motion of the system. In this talk I will present the discovery of a new binary WR system which displays a host of extraordinary features, from exceptionally strong radio, infrared, and X-ray emission to a spectroscopic windspeed of ~3500 km/s. However, proper motion studies of the 12″ spiral dust plume reveal an expansion of only ~500 km/s. I will show the solution to this severe contradiction in system velocities lies in a unique double WR binary composition and a new wind-launch mechanism capable of producing an extreme latitude-dependent wind asymmetry, implying this system could be a local long-duration gamma-ray burst progenitor.

The Milky Way is host to a few hundred billion stars. Of them, about 10 million, less than 0.01%, have so far been mapped by large-scale spectroscopic surveys, such as SDSS, Gaia-ESO, GALAH, and LAMOST. I will show how we can use the detailed chemical composition of stars – a key product of these observational programs – to constrain the history of chemical enrichment in the Galaxy. I will focus on the elements of the iron group and heavier. The synthesis of these elements requires extreme conditions and is associated with a diversity of astrophysical events, including core collapse and thermonuclear supernovae, collapsars, and compact binary mergers. Studying detailed abundance ratios and their trends in stellar populations gives us a unique opportunity to constrain the physics of these events and their stellar progenitor sources. I will describe recent advances in the field and outline the perspectives opening with large facilities of the next decade, such as 4MOST, WEAVE, and SDSS-V.

We are here today because of choices and history that were made yesterday. The covid-19 global pandemichas shifted our normal and given us pause to reconsider this history, our part in the present, and ourresponsibility in shaping the future. How does this apply to astronomers? Our astronomy community sharesa passion for the sky attempting to unlock the mysteries of light, gravity, matter, and the creation of theUniverse. What about other peoples that have kinship with the sky? The night sky is alive with spirit andcountless relationships. The land holds living memory and sacred celestial architecture. Shouldn’t there be a way for both to move forward respectfully and with dignity? Shouldn’t there be a wayfor Indigenous students to participate in STEM without having to sacrifice their cultural identity in order tofully participate? These are hard challenges, but as leaders we rise to the challenge and bring to the table ourability to listen and widen our understanding. The path forward can only be forged by recognizing the pastand acting for our future. Einstein himself said “we cannot solve our problems with the same thinking weused when we created them”.

The Cherenkov Telescope Array is the next-generation observatory for ground-based gamma-rayastronomy. With more than 100 telescopes equipped with state-of-the-art technologies, it will provide anew view of the sky at energies from 20 GeV to more than 300 TeV at unprecedented sensitivity andangular resolution. CTA will be a key instrument in multi-wavelength and multi-messenger astronomy,and its unique capabilities will allow us to explore the most extreme phenomena in the Universe. Forexample, CTA’s very large collection area and rapid slewing are crucial to capture and probe transientphenomena, such as gamma-ray bursts and fast radio bursts. In this contribution, I will present the status of the observatory, introduce its key science projects, andhighlight synergies between CTA and Australian facilities and research interests.

The gravitational wave observatories LIGO, Virgo, and KAGRA have so far shown us a Universe of transient signals from merging black holes and neutron stars. The search is also on for several other classes of signals. In this talk we will first present an overview of recent transient events detected during the first half of the third observing run. In the second half of their third observing runs, the LIGO and Virgo observatories twice detected gravitational waves from the inspiral and merger of neutron stars with black holes. This is the first observation of neutron star-black hole binaries. We will describe the detection and characterisation of this new source of gravitational waves.

The Galactic Centre gamma-ray excess (GCE) has spurred much excitement since its discovery, more than a decade ago, in data from the Fermi space telescope covering the inner Milky Way. The signal is plausibly interpreted as the signature of WIMP dark matter self-annihilation in the Galactic centre. We will show, instead, that it is compellingly explained by gamma-ray emission from the population of old millisecond pulsars (MSPs) belonging to the stellar population of the Galactic bulge. Gamma-ray emission from MSPs belonging to other old stellar populations – for instance in dwarf spheroidal satellites of the Milky Way – can also imitate dark matter signals. It may also contribute non-negligibly to the cosmological, isotropic gamma-ray flux measured at Earth.

Observing the magnetic fields of dwarf interacting galaxies, like the Small Magellanic Cloud (SMC), give us a glimpse into one of the important dynamical drivers in the sorts of galaxies that made up the bulk of galaxies in the early universe as well as today. We have used the Australia Telescope Compact Array (ATCA) to measure Faraday rotation, which indicates the presence of a magnetic field towards 80 sight-lines of the SMC; increasing the number of sight-lines by factor of eight over the previous sample. We find that the SMC has an ordered magnetic field strength (-0.55 microG) on the same order as the Milky Way, with a maximum strength of -6 microG. We also detect Faraday rotation in the surroundings of the SMC, indicating that the magnetic field of the SMC has a large impact on its surroundings. The magnetic field of the SMC shows rough alignment with the magnetic field of the Magellanic Bridge, which hints towards the presence of a magnetic field that extends between the Large Magellanic Cloud (LMC) and SMC; a pan-Magellanic magnetic field. By looking at the magnetic field of the SMC using the ATCA we have paved the way forward for new telescopes like the Australia Square Kilometre Array Pathfinder (ASKAP) and projects like “Polarisation Sky Survey of the Universe’s Magnetism” (POSSUM), which will give high source density of Faraday rotation measurements.

The interpretation of the Faraday Rotation Measure (RM) should be made with caution since that there could be multiple magneto-ionised mediums that contribute to the net Faraday rotation along sight-lines. We introduce a simple test using Galactic diffuse polarised emission that evaluates whether structures emerging in the RM grid are associated with the distant circumgalactic medium (CGM) or the foreground interstellar medium (ISM). We focus on the Magellanic Leading Arm region where a clear excess of RM was reported by McClure-Griffiths et al. (2010). There are two gaseous objects standing out in this direction: the Magellanic Leading Arm and the Antlia supernova remnant (SNR). We recognized narrow depolarised filaments in the 2.3 GHz S-band Polarisation All Sky Survey (S-PASS) image that overlaps with the reported RM excess. This suggests that there is a steep gradient in Faraday rotation in a foreground screen arising from the Antlia SNR. The estimated strength of the line-of-sight component of the magnetic field is B|| ~ 5 μG, assuming that the excess of RM is entirely an outcome of the magnetised supernova shell. Our analysis indicates that the overlap between the RM excess and the Magellanic Leading Arm is only a remarkable coincidence. We suggest for future RM grid studies that checking Galactic diffuse polarisation maps is a convenient way to identify local Faraday screens.

Despite the fundamental nature of cosmic magnetic fields, many questions remain regarding their origin, evolution, and structure. We are able to illuminate these otherwise invisible fields through observations of background polarized radio sources. By measuring the Faraday rotation this polarized emission experiences along the line of sight, we are able to reconstruct the magneto-ionic structure of foreground features, such as the Milky Way Galaxy. This technique would also be applicable to smaller foreground objects, such as galaxies and clusters, however, we are typically limited by the on-sky density of background sources detected by a given radio survey. On behalf of the RACS team, I will provide an overview of observations from the Rapid ASKAP Continuum Survey (RACS); the first all-sky survey undertaken by the Australian SKA Pathfinder (ASKAP). RACS is now the state-of-the-art radio-frequency survey of the Southern sky, with a noise-level of ~300µJy/beam, a resolution of ~15”, and 2.1 million sources detected in total intensity at 888 MHz. Through a collaboration between the observatory and the Polarization Sky Survey of the Universe’s Magnetism (POSSUM) survey teams, SPICE-RACS will catalogue linearly polarized sources from RACS and deliver a background polarized source density 3-5x higher than the current state of the art. I will present linearly polarized observations from a subset of RACS towards the nearby Spica HII region. I will share both our preliminary polarisation catalogue and highlight a number of early science outcomes that will be yielded from these new observations.

We present the first study on the amplification of magnetic fields by the turbulent dynamo in the highly subsonic regime, with Mach numbers ranging from 0.001 to 0.4. We find that for the lower Mach numbers the saturation efficiency of the dynamo increases as the Mach number decreases. Even in the case when injection of energy is purely through longitudinal forcing modes, the saturation efficiency > 0.01 at a Mach number of 0.001. We apply our results to magnetic field amplification in the early Universe and predict that a turbulent dynamo can amplify primordial magnetic fields to ≳10-16 Gauss on scales up to 0.1 parsec and ≳10-13 G on scales up to 100 parsec. This produces fields compatible with lower limits of the intergalactic magnetic field inferred from Fermi gamma-ray blazar observations.

Magnetic fields in the interstellar medium (ISM) of galaxies is amplified and maintained by a dynamo action, whereby a part of kinetic energy gets converted to magnetic energy. A dynamo that produces magnetic structures at scales smaller than the driving scale of turbulence is known as the small-scale dynamo. We explore magnetic structures in the amplifying and statistically steady state of the small-scale dynamo in driven turbulence simulations. Using the Minkowski functionals, we quantify the shape of the magnetic structures produced by the dynamo as magnetic filaments and derive the scalings of the typical length, width, and thickness of these filaments with the magnetic dissipation. We show that all three of these magnetic length scales increases as the magnetic field amplifies. The study would help compare the theory of small-scale dynamo and magnetic filaments seen in various ISM simulations with direct and indirect observations of magnetic filaments in the ISM.

Neutral hydrogen (HI) in the interstellar medium often exhibits as a vast network of filamentary structures. The anisotropy of these HI filaments can be induced by supernova explosions, tidal forces, or magnetic fields. In the Milky Way, nearby HI filaments have been found to be oriented along the ambient magnetic fields traced by polarised starlight, suggesting an important role of magnetic fields in the formation of these neutral structures. We investigate if the same relation holds in the Small Magellanic Cloud (SMC), which harbours vastly different astrophysical conditions compared to the Milky Way. This study has been made possible by the new data from the Galactic ASKAP (GASKAP) survey, which provides an unprecedented combination of angular resolution, velocity resolution, and sensitivity of HI in the SMC. We identified ~100 pc scale HI filaments automatically using the Rolling Hough Transform machine vision algorithm, and carefully compared their orientations with the polarisation angles from a recent starlight polarisation catalogue of the SMC. In this talk, I will present the preliminary results from this work.

The Neutron star Extreme Matter Observatory NEMO is a proposed 2.5-generation kHz gravitational-wave detector designed to study the most extreme matter in the Universe, while also acting as a technology driver for full third-generation instruments. I will give an update of the NEMO project, including predictions for astrophysical and physical discoveries, instrumentation design, and site selection studies.

We motivate and introduce the Low-frequency Australian Megametre Baseline Demonstrator Array (LAMBDA), a concept for a <350-MHz counterpart to the Australian Long Baseline Array (LBA). SKA1-LOW will provide unmatched raw sensitivity at metre wavelengths, but without immediate prospects for delivering sub-arcsecond angular resolution. Australia is well placed to fill this gap by building on our existing VLBI network and expertise in low-frequency instrumentation, establishing an initial long-baseline array operating in the SKA1-LOW spectrum during the years before SKA operations begin. In this presentation we will provide an overview of the science case for such an array, as well as a summary of the resources, challenges and opportunities involved in establishing the LAMBDA project. We will discuss the capabilities that could be enabled by LAMBDA, and the opportunities for linking with additional low-frequency telescopes.

The Australian-led Keck Wide-Field Imager (KWFI) is a proposed 1-degree diameter field of view UV-sensitive optical camera for Keck prime focus. KWFI will be the most powerful wide-field camera in the world and the only such 8m-class camera sensitive down to ∼3000A for the foreseeable future. Australians will have access to KWFI to perform world-leading science that cannot be done on any other telescope or instrument in the world, even in the era of 30-metre telescopes. As a result of the 10m aperture, 4100m elevation, throughput and other aspects, KWFI can reach game-changing m ~ 28 in 2 hrs and m ~ 30 over the wide fields in a dedicated program in the optical including u-band. In addition, a fast deployable secondary mirror in the design will enable a quick switch from KWFI to Keck spectroscopic instruments for multiplexing and new science. Examples of science possible with KWFI wide-field extremely deep u-band and optical depths include: the detection and mapping of the elusive faint Lyman continuum flux from high redshift galaxies responsible for cosmic reionisation, detection and selection of metal-poor stars and other Milky Way populations, accurately measuring the cosmic UV background, enabling deep photometric redshifts, efficient globular cluster and compact galaxy selection, fast radio burst counterpart and fast transient detection to depths where models predict, faint Milky Way satellites and diffuse galaxies, and gravitational wave (GW) counterpart detection, as the next generation of GW detectors will detect most events at distances further than, and fainter than, what can be detected by current telescopes. KWFI will the only instrument that can do this for 2/3rds of the Southern Hemisphere, as well as the only instrument for the full Northern Hemisphere, enabling Australians to lead the world in all these areas of science and more.

Twinkle is a 45cm space telescope launching in 2024 with a spectrograph that in a single image, can take a precise measurement of the brightness of an object with almost continuous coverage from 400nm through to around 4500nm (4.5microns). Once launched Twinkle will live in a roughly polar, eternal-twilight low-earth orbit. Twinkle will be the first dedicated exoplanet atmosphere characterisation survey and will act as a precursor for larger upcoming surveys like ARIEL. The survey will be separated into two main groups of science: studying exoplanetary atmospheres, and characterising Near-Earth Objects in a Solar System with a primary focus on asteroids, comets and moons. In this talk I will present an update regarding the progress of the satellite development, launch readiness, and outline the planned ground-based preparation observations. I am keen to speak to anyone who is interested in working with the data or being part of the science team. I would like to arrange an Australian partnership (funded) buy-in to the Twinkle mission, at no cost to Universities, and so will organise a lunchtime meeting for anyone interested during this meeting.

The Vera C. Rubin Observatory’s Legacy Survey of Space and Time will conduct a ten-year dynamic survey of the Southern hemisphere from 2023-2033. The survey will be undertaken by an 8.4m optical telescope under construction in Chile. LSST will deliver an unprecedented set of images and data products that will address some of the most pressing questions about the structure and evolution of the universe and the objects in it. I will give an update on the status of LSST and Australia’s access to that survey.

On June 1st this year, an Australian-led consortium secured an agreement with the European Southern Observatory (ESO) to build “MAVIS” – a revolutionary new $57M instrument for the Very Large Telescope (VLT) in Chile, and the first ESO facility instrument to be led by Australia. MAVIS will make use of the Adaptive Optics Facility on the 8-meter “Yepun” telescope, exploiting its four laser guide stars and adaptive secondary mirror to deliver near diffraction-limited capabilities at optical wavelengths over a large field of view, and over the majority of the sky – a unique capability of any telescope of this size. MAVIS will facilitate a broad range of science, with both imaging and integral-field spectroscopic capabilities. I will present an overview of the MAVIS instrument, an update on the project status, and highlights from the MAVIS science case, including outcomes from our very recent community science workshop (held one week before the ASA AMS).

Observational studies of star clusters are important to constrain stellar evolution theory and the star formation histories of their host galaxies. Traditionally, star clusters were believed to represent “simple” stellar populations (SSPs), with all member stars reflecting a similar age and a unimodal chemical composition. However, detection of star-to-star abundance spreads in light elements (C, N, O, Na, Mg, Al) in young (~ 1–3 Gyr-old) clusters has revolutionized this field. In the last decade, many young and intermediate-age (~ 3–6 Gyr-old) clusters have been found to display deviations from the SSP concept, particularly in terms of their ages, chemical compositions and rotation rates. I will discuss the simple and complex stellar populations in star clusters in the Magellanic Clouds. We have used Hubble Space Telescope imaging data to investigate the stellar evolutionary stages of young and intermediate-age Magellanic Cloud clusters to understand properties such as their helium and nitrogen abundance variations. Studies of young star clusters in nearby galaxies can provide clues to the star formation history of our own galaxy, the Milky Way.

The transient universe continues to surprise us on the shortest timescales across multiple wavelengths with various new classes of events being discovered over the last ~20 years. Here we will explore the fastest class of stellar flares as discovered by the Deeper, Wider, Faster program, using 20 second continuous DECam imaging as well as the machine learning methods used in our process of flare retrieval.

Measuring ages for individual stars is the holy grail for Galactic Archaeology. Using GALAH DR3, we demonstrate for the first time that is possible to estimate ages for large numbers of stars through Galactic chemical evolution alone. We explore how elemental abundances vary with age and overall metallicity using main sequence turn off stars from GALAH DR3. We find that the abundance of most elements can be predicted from age and[Fe/H] with an intrinsic scatter of about 0.03 dex. Inverting this idea, we also find that age can be directly estimated for all stars in the GALAH survey from stellar chemical abundances. This is the first demonstration that Galactic chemical evolution and chemical tagging can be used to estimate ages for large datasets. We find that the stellar ages for the bulk of the GALAH DR3 sample are accurate to 1-2 Gyr using this method. With these ages, we replicate many recent results on the age-kinematic trends of the nearby disk, including the age-velocity dispersion relationship of the solar neighborhood and the larger global velocity dispersion relations of the disk found using Gaia and GALAH.

The strength of the Solar wind in the deep past is poorly characterised. Tomographic surface magnetic field observations of young, Sun-like stars at different ages can however be used to drive magnetohydrodynamic simulations of stellar wind using models originally developed to study the Solar wind, permitting the calculation of quantities such as the instantaneous total mass- and angular momentum loss. We model the winds of 30 young, Sun-like stars aged between 24 Myr and 0.6 Gyr by driving an extended MHD model with the stellar surface magnetic fields. The resulting three-dimensional wind models enable us to find the stellar angular momentum loss and the expected range of stellar wind pressures in the circumstellar habitable zone. By having a large number of wind models we are able to study the effects of magnetic field strength and complexity while controlling for variations in stellar mass and radius. We find clear trends with stellar age and rotation rate, but also a spread of an order of magnitude at a given age. We tentatively attribute this spread to stellar variability and magnetic cycles. The interplay between magnetic field strength, angular momentum loss, and the stellar rotation rate suggests multiple possible histories for the Solar wind and its effect on Venus, Mars, and the Earth. However, the converging rates of rotation for older Sun-like stars suggest that these histories largely converge around a stellar age of 1 Gyr, that very long-timescale magnetic cycles are uncommon, and that variations in the stellar dynamo do not persist over very long timescales. In this way some bounds on the early history of the Solar wind are found.

Common-envelope evolution has been extensively studied as it constitutes a key step in the classical scenario for forming a range of astrophysical systems: gravitational-wave sources, X-ray binaries, and progenitors of type Ia supernovae. Yet common-envelopes are also one of the least understood phases in binary evolution. I will discuss our recent work on producing some of the first 3D global common-envelope simulations involving massive donor stars, which are qualitatively different from low-mass stars as their envelopes have significant support from radiation pressure, and recombination energy may play a more significant role in envelope ejection. I will discuss how the amount of unbound gas mass, the final separation, and inspiral dynamics are affected by the addition of radiation pressure and ionisation/recombination.

It has been long known that the Milky Way disc has significant vertical and radial age gradients. Using white-light flare emission as a proxy for magnetic activity, we investigate the spatial distribution of M dwarf activity as a function of Galactic position to assess the link between the observed activity trend and age distribution. With the benefit of near-simultaneous multi-colour observations of the SkyMapper DR3, the number of M dwarf flares is increased by factor of 5 compared to the previous work. Based on improved distance measurements from Gaia EDR3, we find a kink in the slope of the flare fraction near 100pc from the Galactic plane (Z) where a steep decline sets in. We also see a weak hint of flattening at larger vertical distances around 400-500pc. In addition to this, we find higher flaring fraction for M dwarfs between 10 < Z < 100 pc than those for negative distance bins (i.e., -10 < Z <-100 pc). In this talk, we will discuss possible explanation of this spatial dependence in the context of the structure and dynamical evolution of the local Milky Way disc.

Active Galactic Nuclei (AGN) feedback is a key ingredient in galaxy formation and evolution. A large portion of this feedback is done by radio jets in the form of shock-heating and uplifting gas. Both theory and observations show that jets are affected by their environment; therefore, to understand jet feedback, a detailed understanding of jet-environment interaction is required. I use numerical hydrodynamic simulations to explore these interactions by simulating both FR I and FR II jets in a range of complex environments. I quantify how the jet dynamics are impacted by the environment and calculate lossy spatially resolved synchrotron emissivities in post-processing to demonstrate the impact of environment on the spectral properties of a radio source.

Studies of young radio galaxies have revealed a correlation between 21cm HI absorption and soft X-ray absorption, two processes which have historically been used independently to probe the dense and dusty central regions surrounding AGN. This correlation has so far been seen most often in CSS/GPS sources, suggesting that the presence of circumnuclear hydrogen is influenced by both age and evolutionary state. I will discuss this in relation to a sample of historic sources, before presenting an analysis of new data collected through the SEAFOG project (Studies of eROSITA And FLASH Obscured Galaxies) which will provide an unbiased sample of hundreds of galaxies observed in the radio and X-ray. I will report on the progress of SEAFOG and discuss some of the early science being done with the eROSITA performance verification field (eFEDS) alongside both FLASH Pilot Survey data and ASKAP data observed as part of the SWAG-X Observatory Project. Finally, I will discuss some of the challenges posed by studying historic samples of radio and X-ray selected galaxies, how these challenges might affect the correlation we observe between HI and X-ray absorption, and how multiwavelength projects like SEAFOG provide a unique opportunity to explore the properties of galaxies in unbiased samples, and on an unprecedented scale.

Using SkyMapper, Gaia, and various IR surveys, we have discovered over 100 new ultra-luminous, high-redshift quasars in the Southern sky, with redshifts confirmed using the ANU 2.3m. This sample is essentially complete at the bright end, and the space density is 3 times higher than comparable searches in the North. In conjunction with known quasars, we have constructed the most precise bright-end z~5 quasar luminosity function so far.

With the very recent discovery of radio luminous AGN at z>6, a new window of opportunity is finally opening in the study of the galaxy evolution at the end of the Epoch of Reionization. Our pilot programme in the 60 deg^2 GAMA-09 field uses a new selection technique taking advantage of the large frequency coverage of GLEAM by selecting compact, steep and curved sources at low-frequency (70-230MHz). Out of four candidates, one new powerful radio galaxy, 0856+0224, is confirmed at z=5.55, finally overtaking the z=5.2 20 year-old record for distant radio galaxies (albeit just falling short of the new recent z=5.7 record). Interestingly, 0856+0224 presents similarities with existing z<5 redshift samples, giving confidence in the success of our selection technique. Our recent progress on a second source, 0917-0012, thanks to the extensive multi-wavelength coverage from follow-up observations with ALMA and JVLA, supplemented with publicly available data, place this source at a promising z>7. I will also discuss the refinement of our selection technique over the full 1200 deg^2 sky area covered by the ESO VIKING near-infrared survey, leading to 55 new high-redshift candidates. This sample aims to provide us with the first statistically significant radio luminous active galactic nuclei sample at z > 6.5 during the Epoch of Reionization. The nature of radio selection presents the advantage of being insensitive to orientation-dependent obscuration, it allows us (i) to study simultaneously the co-evolution of the supermassive black hole and host galaxy and (ii) to enable the study of the IGM through the HI absorption line.

The globular cluster Omega Centauri is the most massive and luminous cluster in the Galaxy. The Gamma-ray source FL8Y J1326.7-4729 is coincident with the core of the cluster, leading to speculation that hitherto unknown radio pulsars or annihilating dark matter may be present in the cluster core. Here we report on the discovery of five millisecond pulsars (MSPs) in Omega Centauri following observations with the Parkes radio telescope. Four of these pulsars are isolated with spin periods of 4.1, 4.2, 4.6, and 6.8 ms. The fifth has a spin period of 4.8 ms and is in an eclipsing binary system with an orbital period of 2.1 hr. Deep radio continuum images of the cluster centre with the Australian Telescope Compact Array reveal a small population of compact radio sources, making it likely that other pulsars await discovery. We consider it highly likely that the MSPs are the source of the Gamma-ray emission. The long-term timing of these pulsars opens up opportunities to explore the dynamics and interstellar medium of the cluster.

Making high-precision measurements of pulsar dispersion measures (DMs), and applying suitable corrections for them in timing data, continue to be one of the major challenges in Pulsar Timing Array (PTA) experiments aimed at the detection of nanohertz-frequency gravitational-wave background produced by supermassive black-hole mergers. While the advent of wide-band receivers and pulsar instrumentation can potentially yield improved (and more precise) DM measurements for timing array analysis, it also necessitate careful assessments of any frequency dependence (chromaticity) in the measured DMs that was predicted by theoretical models of propagation effects due to the interstellar medium. Here we report the detection of such an effect in our observations of PSR J2241-5236, a high-priority target for current and future PTA experiments. The observations were made using the Murchison Widefield Array, the upgraded Giant Metrewave Radio Telescope and Parkes 64-metre telescopes, thus providing a large frequency coverage from 80 MHz to 4 GHz contemporaneously. Our analysis reveals an excess in DM (~ (1-3) × 10^-4 pc cm^-3), that scales with the observing frequency (ν) as ∆ DM ~ ν^{-3.8 ± 0.5}. We will discuss the potential implications of such frequency-dependence for pulsar timing-array experiments and the likely impact on the timing noise budget, and the usefulness of low-frequency observations for progressing toward the ultimate goal of PTAs.

In July 2011, the first results from SAMI – The Sydney-AAO Multi-object IFS – were presented at the ASA-ASM. At the time, the instrument was a prototype wide-field system at the Anglo-Australian Telescope, but would soon become the inspiration for a new generation of spatially resolved galaxy surveys that have changed our way we view galaxies. Now, a decade later, all SAMI Galaxy Survey data have been made public. But what made SAMI a success story? Did we answers all science questions raised in the initial proposal? Is there really a need for another IFS survey such as Hector? Did a Huntsman spider nearly ruin the entire survey? In this talk I will highlight some of the SAMI Team’s most recent results, whilst also reflecting on our achievements in the past ten years.

By and large, flows of gas are what govern the formation and evolution of galaxies. Without inflow channels like cosmological accretion, radiative cooling, and mergers, we’d be without stars and metals. The balance of this with outflows driven by stellar winds, supernovae, active galactic nuclei, and environmental stripping processes like ram pressure is what gives galaxies their properties that we observe. To capture all these effects simultaneously in a theoretical framework requires detailed simulations.
In this talk, I will provide an overview of modern cosmological simulations. I will discuss how we test the outcome of the galaxies that form in these simulations against observational data, with a focus on their gas content at low redshift. Key to this is mock-observing those galaxies to ensure our comparison with the real Universe is fair.

On the largest scales there is the cosmic web; voids, clusters and filaments in a weblike pattern. Synchrotron emission from the magnetic fields pervading the cosmic web is a fundamental feature of the Universe required by theories of large-scale structure formation. Matter falling into and along filaments of the cosmic web creates shocks, accelerating electrons amplifying magnetic fields and producing synchrotron emission. Detecting this emission and measuring its properties tells us about large-scale structure formation and evolution and the role of cosmic magnetism. However, this synchrotron emission is expected to be faint and diffuse, spread over Mpc scales. Thus direct imaging is challenging, as even with the most sensitive telescopes source confusion will dominate.This talk will thus discuss new working using a stacking technique to make a statistical detection of cosmic filaments, what we have learned, and where we go from here.

We present new pilot survey results from the First Large Absorption Survey in HI (FLASH). The FLASH is a blind neutral atomic hydrogen (HI) absorption line survey, searching for both associated and intervening absorbers using the Australian Square Kilometre Array Pathfinder (ASKAP). 21-cm absorption-line spectroscopy is a unique tool to trace the cold neutral gas in galaxies out to high redshift. The FLASH survey is designed to obtain continuous spectral line data in the redshift range from z = 0.4 to 1.0 along the line of sight to background radio sources. Our ultimate goal is to detect more than 1,000 HI absorbers from a 34,000 square degree area of the southern sky. Using the HI absorbers, we aim to determine the evolution of the cold HI in galaxies as a function of cosmic time, as well as probing the physical conditions and kinematics of gas in the central region of radio-loud AGNs. We have recently completed our first 100-hr observations, covering 1,000 square degrees of the selected fields with the full 36-antenna telescope. Our first pilot survey data is ideal for validating observation and data processing. In this talk, we will report on the current status of the FLASH pilot survey, and present the first detections of HI absorption. We will highlight several new detections from associated and intervening absorbers with their line properties, and discuss the origin of the individual absorptions. In addition to the spectra, our high-quality wide field continuum images obtained at the same time from the lowest frequency ASKAP band (700 to 1000 MHz) will also be presented.

Neutral hydrogen (HI) gas is often easily detected beyond the optical disc of a galaxy and is a sensitive probe of the impact of the environment on galaxy evolution. WALLABY is the all-sky HI survey on the Australian SKA Pathfinder (ASKAP), which will be transformational in our understanding of the HI content of galaxies through detecting around half a million galaxies in HI and spatially resolving HI in several thousand of galaxies over ~75% of the sky. Currently underway is the WALLABY pilot survey which has so far observed three 60 square degree fields. This includes the first cluster observed with WALLABY: Hydra I. These observations probe Hydra I out to ~2 virial radii and HI in field galaxies out to ~5 degrees to the West of the cluster with uniform sensitivity and spatial resolution. I will present a HI view of the Hydra I cluster provided by the ~150 HI sources detected by WALLABY in and around Hydra I and the impact of the cluster environment of on the galaxies’ HI properties.

The atomic hydrogen disk of the Milky Way extends far beyond the disk of young stars, molecular clouds, and cosmic rays that are driven by star formation. The outer regions of the Galactic disk are important as an example of the dynamics and thermodynamics of a gas-only environment. In particular, the abundance and distribution in space and velocity of the cool neutral medium, CNM, with kinetic temperature typically 50 to 100 K can be studied by absorption in the 21-cm line. Until now, our knowledge of the CNM in the outer Milky Way has been limited to a few lines of sight toward bright background continuum sources. But now the situation is changing rapidly: the outer disk of the Galaxy will be much better understood as the Australian Square Kilometre Array Pathfinder (ASKAP) telescope begins to survey the Milky Way for project GASKAP. The first observation of a Galactic plane field was centred at longitude 340, latitude 0. There are some 347 continuum sources in this 6×6 degree field that are bright enough to provide useful 21-cm absorption spectra. Roughly half of these continuum sources are Galactic, half extragalactic. The extragalactic sample provides a shadow-map of the CNM disk; the thickness of the disk, its offset from the midplane, and its cloudy structure can be traced as far as 30 to 40 kpc from the Galactic Centre. Results from this pilot field already show the abundance and motion of the CNM in the outer disk much better than anything available from other telescopes. Based on these results we can predict how much we will learn in the next year or two as the main Galactic Plane ASKAP survey progresses.

Detecting large-scale structures in the intergalactic medium (IGM) during cosmic reionisation via absorption of 21 cm spectral line of neutral Hydrogen against a background radiation is a powerful and independent technique complementary to the three-dimensional tomography and power spectrum techniques. The direct detection of this absorption is very challenging because it requires very bright (> 10–100 mJy) background sources at high redshifts (z > 8), which are evidently rare; very long times of integration; or instruments of very high sensitivity. Instead, a statistical approach is found to be significantly more viable using one-dimensional (1D) power spectrum along narrow sightlines but with fainter background objects (<1–10 mJy), which are likely to be more abundant and significant contributors at high redshifts. This approach reduces cosmic variance and improves sensitivity especially on small spatial scales. The prospects of detecting the 1D power spectrum along selected narrow directions are investigated against uncertainties from thermal noise and the chromatic synthesised point spread function (PSF) response. Minimum requirements on the number of high-redshift background sources, the telescope sensitivity, and the PSF quality are estimated for a range of instrumental, background source, and reionisation model parameters. A 1000 hr observing campaign with modern radio telescopes, especially the Square Kilometre Array, can detect the 1D power spectrum on a range of spatial scales and redshifts, and potentially discriminate between models of cosmic reionisation.

The transmission of Lyman-α (Lyα) in the spectra of distant quasars depends on the density, temperature, and ionization state of the intergalactic medium (IGM). Therefore, high-redshift (z > 5) Lyα forests could be invaluable in studying the late stages of the epoch of reionization (EoR), as well as properties of the sources that drive it. Indeed, high-quality quasar spectra have now firmly established the existence of large-scale opacity fluctuations at z > 5, whose physical origins are still debated. In this talk, I will present a 4D Bayesian forward-modelling framework capable of constraining IGM and galaxy properties from forest observations. Using priors from galaxy and CMB observations, I will show that the final overlap stages of the EoR (when > 95% of the volume was ionized) should occur at z < 5.6, in order to reproduce the large-scale opacity fluctuations seen in forest spectra. However, it is the combination of patchy reionization and the inhomogeneous UV background that produces the longest Gunn-Peterson troughs. Lyα forest observations tighten existing constraints on the characteristic ionizing escape fraction of galaxies, with the combined observations suggesting fesc~7%, and disfavoring a strong evolution with the galaxy’s halo (or stellar) mass.

In this talk, I will introduce recent results from the MOSEL survey which is an ongoing spectroscopic survey of emission-line galaxies at z=3-4. MOSEL sample includes about 20 metal-poor (Z<0.1 Zsun), low stellar mass (10^9 Msun) galaxies with high star formation rate (5-10 times the typical star-forming galaxy) and [OIII] equivalent widths (>600 A), making them analogous to EoR galaxies. We have obtained deep KMOS/MOSFIRE spectroscopic and nearly 40-band photometric data for these targets. I will present a preliminary analysis comparing the [OIII] EWs, the production efficiency of the ionizing photons and ionization parameter of EoR analogs and typical star-forming galaxies at z~3. Our data will be an excellent comparison for the future observations of z=6-9 galaxies with JWST.

The development of efficient near-infrared (NIR) spectroscopic facilities for SSO would unlock an entire class of transient events–including dust-obscured and high-redshift supernovae as well as GW counterparts–for study by the Australian community. I will discuss two instrument concepts, WISP and ASPECT, that would enable rapid classification and analysis of transient sources. Combined with DREAMS, WISP and ASPECT would provide a complete facility for NIR transient discovery, classification, and follow-up capitalising on Australia’s unique longitude and expertise in near-infrared instrumentation.

HRMOS is a high-resolution spectrograph for the VLT to carry out breakthrough science across Galactic and Local Group archaeology to Stellar astrophysics and Exoplanet studies. HRMOS fills a gap in capabilities amongst the landscape of future instrumentation planned for the next decade. The key capability of HRMOS is high spectral resolution (60 – 80,000) with multi-object (~100) capabilities and stability that provides detailed spectral information and radial velocity precision (~10m/s), which are otherwise missing and unattainable with the currently planned large surveys such as 4MOST, WEAVE and MOONS. We will describe the initial science drivers and requirements, along with some of the technical options currently considered. We encourage the Australian community to get involved in this exciting project, which builds on to push the boundaries of our knowledge on Australian-led fields of research in Galactic archeology and Stellar astrophysics.

The past 25 years of exoplanet research have shown that exoplanets are abundant, yet many questions of planet formation remain unanswered, with competing and complex theories. There is a lot of evidence pointing to the median planetary system being smaller than our own solar system, which is a key reason why 8-10m class telescopes have struggled to find giant planets in the process of formation. Recent publications have shown that only long baseline interferometry or the best ELT instruments will be able to detect thermal emission from young giant planets in typical solar systems. I will describe the Asgard visitor instrument suite for the VLTI, including the funded European led BIFROST and VIKiNG instruments, as well as the Australian components Heimdallr and Baldr which are in the planning stages, enabling the highest contrast nulling interferometry. In particular, I will demonstrate through simulated performance that the complete instrument suite will be unique for the next 20 years for imaging and answering key questions of planet formation.

The ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) is a $40M Centre of Excellence, which is producing a comprehensive picture of the build up of mass, angular momentum, and the chemical elements from the first stars, to (and including) the Milky Way. Our surveys include the measurement of the power spectrum at the Epoch of Reionization with the Murchison Widefield Array, large HI surveys with the Square Kilometre Array Pathfinder, the ongoing Australian optical integral field surveys of 10^5 galaxies, a large galaxy evolution program combining HST, Keck, and ESO spectroscopy of galaxies across 12 billion years of cosmic time and the major Australian Galactic Archaeology program to track the chemical history and accretion history of our Milky Way. ASTRO 3D has ambitious diversity and inclusion programs, and has recently achieved 46% women across the Centre. I will describe the recent scientific discoveries made in ASTRO 3D, as well as providing an update on our equity and diversity programs, and my recent research into diversity in the broader Australian astronomy community.

High mass X-ray binaries are systems where a compact object accretes matter captured from the stellar wind of a massive companion star. The wind is usually driven by radiative forces from the donor star. In close binary systems, the donor star can be distorted from spherical symmetry due to rotation and tides. In addition, it is known that stars can suffer gravity darkening due to the reduction in effective gravity because of the centrifugal and tidal forces. Since the wind is driven by radiation, the wind morphology could be greatly impacted by these effects. In this talk I will discuss the possible effects of the asphericity of stars in close binaries on the wind morphology and accretion onto the compact object in high-mass X-ray binaries.

In the era of time-domain astrophysics, observations of stellar mergers are multiplying rapidly, but the theoretical interpretation is lagging. We have developed a new 3D hydrodynamics code that specialises on stellar mergers. The innovation derives from a close collaboration between computer science and astrophysics that resulted in a highly scalable 3D hydro code with superior conservation properties and that can run on hybrid architectures (CPU-GPU and ARM-based). I will present a suite of early results that demonstrate the power of this new tool and its possible role in solving some of the most complex stellar binary problems approachable by 3D hydrodynamics. Finally, I will recount the role that Astrophysics has plaid in developing a technology useful in other arenas.

Obtaining a detailed census of galaxy properties through cosmic time is crucial to our understanding of galaxy evolution, but depends critically on our ability to correct for the effects of dust attenuation. Dust attenuation curves appear to evolve significantly between z=0 and z=2, however, the underlying cause of this evolution remains unclear. Constraints on attenuation curves at z~1 can provide clear progress on this issue. We present a characterization of dust attenuation curves at z~1 based on combining rest-frame UV-to-NIR photometry with HST grism surveys (WISP and 3D-HST), which provide dust-sensitive emission line diagnostics, for ~1500 galaxies at 0.7 < z < 1.5. We find that the average z~1 dust curve lies in-between previous z=0 and z=2 curves. We explore the dependency of the curve shape on galaxy properties by subdividing the sample to provide insight into the redshift evolution.

After the scientific success of the wide field gamma ray observatories in the Northern Hemisphere, such as HAWC in Mexico and LHAASO in China. The SWGO collaboration is planning the construction of the next generation wide field gamma ray observatory somewhere in the Southern Hemisphere. The SWGO observatory will monitor the gamma ray activity from the Galactic Centre region and from galactic and extra-galactic sources that are only visible from the Southern Hemisphere. Its energy range sensitive will expand from 100s Gev to PeV energies. It will be based on ground-level particle detection, with close to 100% duty cycle and order steradian field of view. With an area considerably larger than HAWC (comparable with LHAASO) and significantly better sensitivity, and a low density outer array. The SWGO observatory will be complementary to CTA, it will assist to identify in real time transit events. Furthermore, it will contribute to cosmic ray mass composition studies and also to studies of high energy hadronic interaction properties. Such observations will be analysed together with observations from the Pierre Auger Observatory in order to cover a very wide energy range up to 100 EeV.

I will provide a status update on the Parkes Pulsar Timing Array project and related international timing arrays. The timing arrays are detecting signals that may be the first evidence of ultra-low-frequency gravitational waves. I will show the current results and discuss their implications. Even though new, highly sensitive telescopes are now observing millisecond pulsars (such as MeerKAT and FAST), I will argue that the Parkes telescope (and its unique instrumentation suite) has an important role to play into the foreseeable future.

The ESA Gaia astrometric mission has enabled the remarkable discovery that a large fraction of the stars near the Solar neighbourhood appear to be debris from a single in-falling system, the so-called Gaia-Enceladus. One exciting feature of this result is that it gives astronomers for the first time a large sample of easily observable, unevolved stars that formed in an extra-Galactic environment, which can be compared to stars that formed within our Milky Way. In this talk I will discuss using these stars to investigate the “Spite Plateau” – the near-constant lithium abundance observed in metal-poor dwarf stars across a wide range of metallicities (-3 < [Fe/H] < -1). In particular our aim was to test whether the stars that formed in Gaia-Enceladus show a different Spite Plateau to Milky Way stars that inhabit the disk and halo. Individual galaxies could have different Spite Plateaus – e.g., the interstellar medium could be more depleted in lithium in a lower galactic mass system due to it having a smaller reservoir of gas. We find that the Gaia-Enceladus stars show the same lithium abundance as other likely accreted stars and in situ Milky Way stars, strongly suggesting that the “lithium problem” is not a consequence of the formation environment. This result fits within the growing consensus that the Spite Plateau, and more generally the “cosmological lithium problem” – the observed discrepancy between the amount of lithium in warm, metal-poor dwarf stars in our Galaxy, and the amount of lithium predicted to have been produced by Big Bang Nucleosynthesis – is the result of lithium depletion processes within stars.

One of the key open questions in extragalactic astronomy is what stops star formation in galaxies. While it is clear that the cold gas reservoir, which fuels the formation of new stars, must be affected first, how this happens and what are the dominant physical mechanisms involved is still a matter of debate. In this talk, I will review the current status of environmental studies of cold gas in star-forming satellites in the local Universe from an observational perspective, focusing on the evidence for a physical link between cold gas stripping and quenching of the star formation. I will show that stripping of cold gas is ubiquitous in satellite galaxies in both group and cluster environments. While hydrodynamical mechanisms such as ram pressure are important, the emerging picture across the full range of dark matter halos and stellar masses is a complex one, where different physical mechanisms may act simultaneously and cannot always be easily separated. Most importantly, we show that stripping does not always lead to full quenching, as only a fraction of the cold gas reservoir might be affected at the first pericentre passage. We argue that this is a key point to reconcile apparent tensions between statistical and detailed analyses of satellite galaxies, as well as disagreements between various estimate of quenching timescales.

How did accreted stars and mergers in the Milky Way influence the formation of the Galaxy? In order to answer this question, we first have to identify such accreted stars by means of chemical and dynamical information. How (dis-)similar are selections of accreted stars when performed in dynamical and chemical space? I will present which elements and nucleosynthesis channels show the most significant separation for accreted stars within GALAH DR3 (a large data set of stellar spectroscopic measurements). I will assess how the chrono-chemodynamic properties of these chemically tagged stars compares to common dynamical selection (based on orbit information like orbit energies and actions). The overlap of these selection, but especially the stars that do not overlap are most interesting as they could hold key information for the beginning, duration, and end of the merger of accreted structures.

The stellar halos surrounding large galaxies like the Milky Way and Andromeda (M31) are made up of the remnants of smaller satellites that have been accreted and destroyed over cosmic time. They constitute a fossil record of this process, and can, in principle, be used to reconstruct the formation history of the host. I will report our ongoing efforts to use globular clusters — luminous halo tracers — to piece together the formation history of M31, the nearest giant galaxy to our own. M31 possesses a much more luminous stellar halo than the Milky Way, criss-crossed with stellar streams and over-densities from accreted satellites. Many remote globular clusters in this system closely trace the streams, while others appear associated with a smoothly distributed halo component. These two distinct populations exhibit strong perpendicular rotation, and likely reflect two major accretion epochs separated by billions of years. High precision measurements of globular clusters from the Hubble Telescope are allowing us to trace the sub-structured halo in three dimensions for the first time and will facilitate future modelling of recent accretion events.

I will present the discovery of a rare close binary system, SMSS J160639.78-100010.7, comprised of a magnetic white dwarf with a field of about 30 MG and a brown dwarf. We measured an orbital period of 92 minutes which is consistent with the photometric period. Minimum and maximum light occur at the orbital quadratures and cannot be caused by reflection on the brown dwarf, but, instead, by a spot on the synchronously rotating magnetic white dwarf. The brown dwarf does not fill its Roche lobe and the system may be in a low-accretion state or due to its old kinematical age it is now in a detached state following episodes of mass transfer. SMSS J160639.78-100010.7 is the nearest known magnetic white dwarf plus brown dwarf system.

The results from ESA’s Gaia astrometric mission and deep photometric surveys have revolutionised our knowledge of the Milky Way. There are many ongoing efforts to search these data for stellar substructures to find evidence of the individual accretion events that built up the Milky Way and its halo. One of these newly identified features, called Nyx, was announced as an accreted stellar stream traveling in the plane of the disk. Using a combination of elemental abundances and stellar parameters from the GALAH and APOGEE surveys, we find that the abundances of the highest likelihood Nyx members are entirely consistent with membership of the thick disk, and inconsistent with a dwarf galaxy origin. We conclude that the postulated Nyx stream is likely simply a high-velocity component of the Milky Way’s thick disk. With the growing availability of large data sets including kinematics, stellar parameters, and detailed abundances, the probability of detecting chance associations increases, and hence new searches for substructure require confirmation across as many data dimensions as possible.