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Colloquia Series

For more information on colloquia at the Centre for Astrophysics and Supercomputing please contact Dr. Simon Stevenson ()

Swinburne Virtual Reality Theatre
AR Building, Room 104
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2021 Colloquia

Tuesday Dec 14, 10:30
Mitchell Dixon ()
Student Review: MCR
Thursday Dec 9, 10:30
Deborah Lokhorst (NRC Herzberg)
Colloquium: Directly imaging the circumgalactic medium of local galaxies with the Dragonfly Telephoto Array
The circumgalactic and intergalactic media contain the majority of baryonic matter in the universe and are vital for fuelling star formation in galaxies, yet remain poorly understood due to their near invisibility. At high redshift, direct imaging of these gaseous components has been successful with recent technological upgrades, but at low redshift, where discrepancies in the mass baryon budget arise, these measurements are more difficult to accomplish. The Dragonfly Telephoto Array is a telescope specially designed to image low surface brightness structures, such as large and faint galaxies, and may be uniquely suited to imaging the low redshift circumgalactic and intergalactic media. In this talk, I will describe an upgrade to the Dragonfly Telephoto Array that implements ultra-narrow bandpass imaging capability on the telescope for carrying out this imaging. I will present the results from a pathfinder version of the upgraded Dragonfly, the Dragonfly Spectral Line Imager, and the plans for the full upgrade which will be on sky in early 2023.
Tuesday Dec 7, 14:00
Grace Lawrence (Swinburne)
Student Review: Grace Lawrence DTR
Thursday Dec 2, 10:30
Monse Martinez (Swinburne)
Student Review: Monse Martinez CoC review - Stellar populations and machine learning
Tuesday Nov 30, 10:30
Hasti Nateghi (Swinburne)
Student Review: Hasti Nateghi's MCR
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Thursday Nov 18, 10:30
Themiya Nanayakkara (Swinburne)
Colloquium: Stellar populations in the early Universe with JWST and VLT
The long awaited launch of the James Webb Space Telescope (JWST) in December will be a turning point in observational astronomy. With the space based near and mid infrared observations, we will be able to push the boundaries of extragalactic observational astronomy to the earliest of cosmic epochs. In my talk I will discuss how JWST will help us break the current limitations in galaxy observations in the re-ionisation era. I will show how JWST will provide tight constraints to the formation histories of the z~3-5 quiescent galaxies and how with the combination of VLT observations, properties of the massive stars that dominate the early Universe can be studied in great detail. I will also briefly introduce the the James Webb Australian Data Centre (JADC) and our plans to help the Australian community with JWST science.
Tuesday Nov 16, 10:30
Jonah Gannon (CAS)
Student Review: Jonah Gannon's DTR
Jonah Gannon's DTR

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Thursday Nov 11, 10:30
Karl Glazebrook (Swinburne)
Colloquium: The next generation Real Time Controller for Keck All Sky Precision Adaptive Optics
Keck observatory is going through a major upgrade of its Adaptive Optics System covering hardware, software and control systems to deliver even better performance over more of the sky. A key component of this is the Real Time Controller which computes adaptive optics wavefront corrections at khz speeds. The new RTC is a partnership of Microgate Corp., Swinburne, ANU and PSL to build a flexible system taking advantage of the speed of modern GPUs that can easily be reprogrammed to support dozens of modes. This is the first of a new design approach for RTCs and we are in the final stages of commissioning this on-sky at Keck.
Thursday Oct 28, 16:00
Pratika Dayal (The University of Groningen)
Colloquium: Early galaxy formation & its large-scale effects: challenges in the era of SKA, Euclid and LISA
Galaxy formation in the first billion years mark a time of great upheaval in the history of the Universe: as the first sources of light, these galaxies ended the 'cosmic dark ages' and produced the first photons that could break apart the hydrogen atoms suffusing all of space starting the process of cosmic reionization. As the earliest building blocks, the galaxies that formed in the first billion years also determine the physical properties of all subsequent galaxy populations. However fully coupling galaxy formation with large-scale reionization remains a massive computational challenge as a result of the range in (mass and volume) scales required. I will start by introducing the Astraeus framework that is the largest (230 Mpc box) and most highly resolved (DM resolution mass of 10^6.9 solar masses) simulation to fully couple a semi-analytic model of galaxy formation with a semi-numerical scheme for reionization (feedback) to shed light on galaxy formation at cosmic dawn. I will then show how cross-correlations of 21cm data with the underlying galaxy population, in the forthcoming era of 21cm cosmology, will yield tantalising constraints on the average intergalactic medium ionization state as well as the reionization toplogy (outside-in versus inside-out). Finally, I will try to give a flavour of how the assembly of early galaxies, accessible with the forthcoming James Webb Space Telescope, can provide a powerful testbed for Dark Matter models beyond "Cold Dark Matter".
Tuesday Oct 26, 10:30
Liyu Ambechew ()
Student Review: DTR Liyu Ambechew
Thursday Oct 21, 16:00
Leindert Boogaard (MPIA)
Colloquium: Cold gas in distant galaxies
Cold gas is the fuel for star formation and mapping the evolution of the cosmic molecular gas content is therefore key to our understanding of the build-up of galaxies over cosmic time. The advent of large millimeter interferometers now makes it possible to map the cold gas content of the universe in unprecedented detail. In this talk, I will present the latest results from the ALMA Spectroscopic Survey of the Hubble Ultra Deep Field (ASPECS), an ALMA large program that performed the largest three dimensional spectral-scan survey for cold gas and dust through cosmic time. I will discuss the resulting physical properties and conditions inside the cold interstellar medium of star-forming galaxies at cosmic noon, and the implications of ASPECS for the cosmic molecular gas density and the baryon cycle.
Tuesday Oct 19, 10:30
Shingo Tanigawa (CAS)
Student Review: Shingo Mid Candidtature Review
Tuesday Oct 19, 15:00
Burak Dogruel ()
Student Review: MCR: Fundamental Scaling Relations among Galaxies in the Local Universe
Thursday Oct 14, 10:30
Laura Driessen (CSIRO)
Colloquium: Commensal searches for variable radio sources with MeerKAT
New wide-field, sensitive radio instruments are enabling us to search and investigate the dynamic radio sky like never before. Previous untargeted radio searches in the image plane have been limited by small fields of view, combining observations from mismatched surveys and instruments, and large gaps between epochs. Now instruments such the MeerKAT, ASKAP, the Karl G. Janksy VLA, LOFAR, and the MWA are uncovering large samples of dynamic radio sources without performing targeted searches. ThunderKAT is the MeerKAT large science project for searching for and investigating variable and transient radio sources in the image plane, and has already revealed exciting results on relativistic binaries, cataclysmic variables and more. A key part of ThunderKAT's goals is to perform untargeted, image-plane searches for variable and transient sources. I will present MKT J170456.2-482100, the first transient discovered with MeerKAT, and 25 new variable radio sources discovered with MeerKAT in the image-plane.
Thursday Oct 7, 10:30
Evegni Grishin (Monash)
Colloquium: Gravitational Wave Mergers from Extreme Orbital Evolution of Few-Body Systems
Triple and multiple systems are ubiquitous in nature and arise in many different scales and configurations. In hierarchical triple systems, the inner binary is perturbed by a distant companion. For large mutual inclinations, the Lidov–Kozai (LK) mechanism secularly excites the eccentricity of the inner binary to large values. We analytically study the breakdown of the secular approximation and find that the maximal eccentricity is generally enhanced, allowing closer encounters between the inner binary components, leading to a plethora of possible outcomes. For compact objects, we include general relativistic corrections and find a lower bound for the maximal eccentricity in 2.5 Post-Newtonian evolution. We use direct integrations to show that the merger rate of binary Black Holes and Neutron Stars in individual galactic nuclei is greater than previously considered by an order of magnitude, but the final rate is uncertain due to uncertainties in star formation history and supply rate. In addition, we briefly present a new type of GW signal from the inspiraling binary during the common envelope phase, where the energy loss is due to dynamical friction rather than GW dissipation.
Tuesday Oct 5, 10:30
Student Review: Hao Ding DTR
Thursday Sep 30, 14:00
Pravir Kumar ()
Student Review: Pravir Kumar Draft Thesis Review
Thursday Sep 30, 10:30
Anais Moller (Swinburne)
Colloquium: Fink broker enabling time-domain science with Rubin Observatory
During the next decade, the Vera C. Rubin Observatory (VRO) will obtain high-resolution optical images of the Southern Sky at unprecedented depths. VRO public alert stream will communicate the detection of up to 10 million of potential transient objects every night. The key to exploit this stream is to be able to select promising transients and automatically connect them with follow-up facilities and science teams. I will introduce Fink broker, designed for real-time analysis of this stream using state-of-the-art big-data and machine learning technologies. Fink will be one of the only brokers around the world receiving the full VRO data stream. In this talk, I will highlight the potential of Fink in multi-wavelength/messenger astronomy and supernova cosmology. I will also discuss the potential of connecting VRO time-domain data with Australian science teams and follow-up facilities with Fink.
Thursday Sep 16, 10:30
Johannes Lange (UCSC)
Colloquium: Probing Cosmic Structure Growth with Large-Scale Structure Surveys
Our canonical picture of cosmology, the Lambda Cold Dark Matter (LCDM) model, has been remarkably successful in explaining a large variety of different observations. However, in recent years, apparent tensions in this standard model have started to appear, sparking interest in alternative cosmological models. Cosmic structure growth as probed by large-scale structure (LSS) galaxy surveys is one of the most sensitive probes of dark energy and physics beyond LCDM. I will summarize recent results from LSS surveys focussing on weak gravitational lensing and will discuss the possibility of a cosmological S_8-tension. Afterwards, I will present recent efforts to maximize the information content we can extract from LSS surveys through simulation-based full-scale cosmological studies. I will discuss how the "lensing is low" problem can illuminate our understanding of cosmic structure growth as well as galaxy formation physics. Afterwards, I will present a full-scale study of the redshift-space galaxy correlation function. I show that such an analysis yields some of the tightest constraints on the cosmic growth-rate of the Universe to date.
Tuesday Sep 14, 10:30
Ayushi Mandlik ()
Student Review: Ayushi Mandlik MCR
Thursday Sep 9, 10:30
Emma Ryan-Weber (Swinburne)
Colloquium: How to pitch a Nature or Science paper
During this colloquium time slot we will holding a discussion featuring CAS staff panel members: Ivo Labbe, Matthew Bailes, Karl Glazebrook.

Publications in the journals Science and Nature are highly valued by the University and contribute to researcher's esteem in applications for research prizes, grants, jobs and promotions. The upcoming Keck (29 Sept) and ESO (23 Sept) telescope proposal deadlines has prompted the question of what type of observation and/or theory makes a Nature-worthy result. The panel members have been invited to share their 1) knowledge on what makes a good pitch to Science/Nature; 2) the difference between submitting to these and 'standard' journals; 3) lessons learned from rejected manuscripts.
Thursday Sep 2, 10:30
Timothy Carleton (Arizona State University)
Colloquium: Formation and Evolution of Ultra Diffuse Galaxies
Ever since the identification of a large population of Ultra-Diffuse Galaxies (UDGs) in the Coma Cluster, there has been renewed interest in the properties of low-surface brightness galaxies. Evidence from the abundance and morphologies of UDGs suggest that cluster environments play an important role in the evolution of these unique systems. Motivated by this evidence, I will present a model for the formation of UDGs through tidal heating of dwarf-elliptical galaxies in clusters. While this model is able to reproduce many aspects of the observed UDG population, including the size distribution and the dependence of UDG abundance with cluster mass, this picture becomes more complicated when considering low-surface brightness galaxies in the field and high-surface brightness galaxies in clusters. To further investigate these systems, I will discuss how the archival HST project SKYSURF will improve our understanding of UDGs and the low-surface-brightness Universe in general.
Thursday Aug 26, 10:30
Tania Barone (Swinburne)
Colloquium: PhD thesis: The link between a galaxy’s structure and its stellar population
In this thesis we analyse the observational relations between galaxy structure and global stellar population properties to determine the dependencies between a galaxy's star formation and mass assembly histories. Stellar population parameters correlate with a range of galaxy properties, but it is unclear which relations are causal and which are the result of another underlying trend. The well-established correlations between mass and other galaxy properties are often considered evidence for mass driving a galaxy's evolution. However, we find that, at fixed mass, stellar population properties show significant dependence on size, indicating that the size of a galaxy is also an important property tracing, and possibly influencing, its evolution. The focus of the thesis is to quantitatively compare trends between various stellar population properties and key galaxy structural parameters --- in particular the galaxy's mass, gravitational potential, and surface density --- in order to determine which relations are intrinsically tighter and are therefore more likely to reflect a causal relation. We divide our work into three parts focusing on early-type galaxies, star-forming galaxies and micro high-redshift galaxies, respectively. This division reflects both the physical differences between these samples, as well as technical differences in measuring their stellar population properties.
Thursday Aug 19, 10:30
Benjamin Pope (University of Queensland)
Colloquium: All Downhill from Here: What Automatic Differentiation can Do for Optics
In order to directly image exoplanets, it is necessary to have both very well calibrated optical systems to suppress starlight (for example interferometers or coronagraphs), and equally sophisticated data analysis software to tease tiny planetary signals out of noise. The main limitation is optical aberrations, whether the distortion of telescope optics or the turbulence of the atmosphere, which produce speckles that can be difficult to distinguish from real planets. The technology underlying deep learning - automatic differentiation or 'autodiff' - offers a solution to both hardware and software design. Autodiff allows us to take derivatives by the chain rule of arbitrary numerical simulations, for example taking the gradient of any figure of merit with respect to the phase of incoming light. This can be used for phase retrieval in highly nonlinear regimes. We can optimize phase masks and other optical designs directly with respect to objective functions like astrometric precision or light suppression. By doing perturbation theory we can also see how noise propagates and construct linear self-calibrations like generalized closure phases. By rewriting the popular optical simulation package 'poppy' to do derivatives, we present 'morphine', a powerful new open source tool for optics and data analysis. While we have developed this for astronomy, the same ideas are applicable to many technologies involving spatial light modulators, phase masks, and related devices.
Thursday Aug 12, 10:00
Thilina Heenatigala (ELSI & NAOJ)
Colloquium: Perspectives on Decolonising Astronomy
A form of colonisation exists in scientific academia, education and outreach. It is identified through the imbalance of power and wealth between academia in developed and developing countries, Global North and Global South, and Western to East. Also recognised as 'parachute science' wherein experts from former mention regions would go into under-developed or Global Southern regions for one-off activities without collaboration with local expertise or long-term plans. The issue of 'colonial science' is reflected in astronomy research, development, education and outreach. These colonial structures continue to shape astronomy efforts, which could work against the development of under-developed communities. As a community of astronomy experts, it is essential to consider how resources such as expertise, guidance, and materials are shared among the communities. And collaborations that go hand-in-hand with local experts and address local needs. This talk will address the growing concern of 'parachute science' or 'colonial science' in the astronomy field.
Thursday Aug 5, 16:00
Alexandra Amon (Stanford)
Colloquium: The Dark Energy Survey Year 3 Results from Weak Lensing and Clustering
I will present the cosmological weak lensing and clustering results from the Dark Energy Survey (DES) using its first three years of data taken using the Dark Energy Camera on the 4m Blanco telescope at CTIO. This analysis spans the full DES footprint, more than 4000 sq. deg. of sky, with the final shear catalogue containing more than 100 million galaxies, constituting the most powerful weak lensing dataset to date. The comparison of DES cosmological constraints from these probes in the low-redshift Universe to CMB constraints provides an unprecedented test of the standard cosmological model, across cosmic time. We find these DES results are consistent with those from the cosmic microwave background (CMB) and support the standard cosmological model, LCDM. I will mention the main challenges that our analysis is susceptible to, and then summarise the DES-Year 3 approach to account for these and deliver robust cosmological constraints.
Tuesday Aug 3, 10:30
Suei Hei (Dexter) Hon (CAS / Swinburne)
Student Review: Suei Hei (Dexter) Hon Draft Thesis Review (DTR)
Progress report on the search for compact massive spheroids at z=0.
Thursday Jul 29, 10:30
Romy Pearse, James Murray and Karl Glazebrook (AAL)
Colloquium: AAL Member Update to Swinburne University of Technology
AAL will be presenting a general update to staff at Swinburne University of Technology on our activities of the past year (or so), as well as current projects and funding arrangements – we will also happily take questions and encourage real-time feedback via our new online platform, WooClap (see more on this below). We have had some staff and Board changes since we last updated the team at Swinburne, so we will touch on these as well. The update will be general in nature, but will also show Swinburne’s involvement with AAL via key project/member representatives and those who serve on our committees. It is hoped that this presentation will introduce AAL to new staff at Swinburne or provide a refresher for those within the department who haven’t been in touch with us for a while.
Tuesday Jul 27, 10:30
Simon Goode ()
Student Review: Artificial Intelligence for Fast Data Analysis and Fast Transient Detection Applications
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Thursday Jul 22, 10:30
Lankeswar Dey (TIFR)
Colloquium: Confirming the presence of a supermassive black hole binary in OJ 287 using multi-wavelength observations
The observed quasi-periodic doubly peaked high-brightness flares in the 130-year long optical lightcurve of blazar OJ 287 is best explained by its binary black hole (BBH) central engine model, where a supermassive secondary black hole (BH) orbits a more massive primary BH in a relativistic eccentric orbit. In this model, the doubly peaked flares arise due to impacts of the secondary BH with the accretion disk of the primary twice every orbit. This model is successful in predicting the starting time of the last three flares, and the latest one was observed during August 2019 with the Spitzer space telescope. The observations of these predicted flares strongly suggest the presence of an SMBHB that inspirals due to the emission of nanohertz gravitational waves (GWs) as the central engine of OJ 287. Additionally, the high-resolution Very Long Baseline Interferometry (VLBI) observations of OJ 287 reveal that its radio jet's position angle (PA) exhibits systematic temporal variations. These variations can arise from the precession of the radio jet of OJ 287 due to the binary nature of its central engine. A recent analysis reveals that the BBH central engine model, primarily developed from the optical observations, can naturally explain the temporal variations in the radio jet PA of OJ 287, observed at 86, 43, and 15 GHz frequencies. Furthermore, the ongoing and future Global mm-VLBI Array (GMVA) campaigns on OJ 287 have the potential to firmly establish the validity of our model. These considerations make OJ 287 an excellent candidate for the nascent field of multimessenger nanohertz GW astronomy, expected to be inaugurated by the International Pulsar Timing Array (IPTA) consortium during the present decade.
Thursday Jul 8, 10:30
Rebecca Davies (Swinburne)
Colloquium: The Impact of Outflows on Galaxies and Halos over Cosmic Time
Outflows are likely to play an important role in shaping the growth and evolution of galaxies, especially at the peak epoch of star formation (z~1-3) where outflows are ubiquitous. Detailed measurements are now required to better constrain feedback models and to establish how outflows influence the properties of interstellar and circumgalactic gas. In this talk, I will highlight results of two recent spatially resolved studies of outflows at z~2, focusing on the launch mechanisms of star-formation-driven outflows and the variety of ways in which outflows couple AGN accretion energy to gas on nuclear, galactic and circumgalactic scales. Finally, I will discuss ongoing efforts to make robust measurements of the abundances of metal ions in the circumgalactic medium at z>5.5, with the goal of understanding the mechanisms governing the production and transport of metals in the early Universe.
Thursday Jul 8, 14:00
Rahul Sengar ()
Student Review: Draft Thesis Review: Rahul Sengar
Draft Thesis Review for Rahul Sengar. Apologies for the unusual time as we are trying to avoid ASA and Amaldi conferences.

Wednesday Jul 7, 10:30
Student Review: Marcus Lower: Draft Thesis Review (Title TBC)
Tuesday Jul 6, 10:30
Mohsen Shamohammadi (Swinburne)
Student Review: Mid Candidature review: Mohsen Shamohammadi
Thursday Jul 1, 10:30
Christopher Fluke (Swinburne University of Technology)
Colloquium: What's the point of humans*? [* for data-intensive visual discovery]
The on-going growth in the size (volume) and collection rate (velocity) of modern datasets poses many changes for traditional visualisation-based knowledge discovery processes. Indeed, in many instances, the vast majority of the data that is collected will never be viewed by a human. Instead, there is an expectation that automated discovery systems utilising artificial intelligence and machine learning methods will be responsible for most of the analysis. What, then, is the point of humans, particularly in fields where visual discovery has played a prominent role? In this talk, I will provide an overview of highlights of my previous work addressing the specific data visualisation needs of one important class of humans: astronomers. This serves as motivation for addressing the collaborative, tactical, time-critical decision-making challenges presented by the Deeper Wider Faster astronomy program, which aims to detect the fastest transient objects in the Universe. Lessons learnt from studying astronomers in their natural habitat has broader applicably to the development of “Cyber-Human Discovery Systems”, where we seek to find a balance between automated discovery and human-centred insight in order to maximise the potential for discovery.
Thursday Jun 17, 10:30
Jeremy Webb (University of Toronto)
Colloquium: Revealing the Milky Way’s Dissolve Star Cluster Population with Dynamics and Chemistry
The Milky Way consists of a large number of star clusters, with over 150 being labelled as old, metal poor globular clusters and thousands being labelled as young, metal-rich open clusters. However these numbers are small compared to the total number of clusters that have ever existed in the Milky Way, as most have fully dissolved between their time of formation and the present day. Most of the constraints that have been placed on the Milky Way’s dissolved star cluster population have been made by extrapolating how the star cluster initial mass function, initial size function, and formation rate have evolved over time. In this talk, I will introduce some more direct ways of studying dissolved star clusters that make use of internal star cluster dynamics, orbital dynamics, and chemical tagging. More specifically I will introduce a new method for constraining progenitor cluster properties through deep observations of stellar streams and how stellar siblings can be identified through the combined use of orbital dynamics and chemical tagging.
Thursday Jun 10, 16:00
Khyati Malhan (Stockholm University)
Colloquium: The LMS-1 stream: A fossil remnant of the early formation of the Milky Way
As per the ΛCDM cosmological model, the halo of the Milky Way was built up by the merging of numerous progenitor galaxies, as these dwarf galaxies brought in their own stellar populations (in the form of stars and globular clusters). Over time, the dwarf galaxies were tidally stripped by the Galactic potential, eventually leading to the formation of “stellar streams”. Therefore, stellar streams provide direct evidence of the hierarchical formation of our Galaxy.

Surprisingly, most of the known dwarf galaxy streams are dynamically-young systems that were only recently merged into our Galaxy (<~3-6 Gyr ago). However, the hierarchical paradigm of galaxy formation suggests that several dwarf galaxies must have merged into the Milky Way at earlier times (>~8−10 Gyr ago). These dynamically-old streams are likely to be discovered in the inner <~10-20 kpc regions of the Galaxy, and they hold the key to unravel the early formation history of the Galactic Halo.

I will talk about the “LMS-1” stellar stream, that we detect by searching for wide streams in the ESA/Gaia EDR3 dataset using our own STREAMFINDER algorithm. We detect LMS-1 as a 60° long stream to the north of the Galactic bulge, at a distance of ~15 kpc from the Galactic center, together with additional components that suggest that the overall stream is completely wrapped around the inner Galaxy. Using spectroscopic measurements from LAMOST, SDSS and APOGEE, we infer that the stream is very metal poor (⟨[Fe/H]⟩=−2.1) with a significant metallicity dispersion (σ [Fe/H]=0.4), and it possesses a large radial velocity dispersion (σ_v = 20 ± 4 kms−1). These estimates together imply that LMS-1 is a dwarf galaxy stream. Both the orbit and metallicity of LMS-1 are remarkably similar to the globular clusters NGC~5053, NGC~5024 and another stellar stream “Indus”. Even Pal~5 cluster overlaps with LMS-1 in the dynamical energy-action (E,J) space. These findings make LMS-1 an important contributor to the stellar population of the inner Milky Way halo.
Thursday Jun 3, 10:30
Haiyang Wang (ETH)
Colloquium: Comparative Planetology: From Stars to Planetary Atmospheres
Comparative Planetology is a terminology initially used for comparing our Earth to other solar system bodies to understand their similarities and differences. With the discovery of thousands of extrasolar planets (among them many are potentially terrestrial), this terminology has been increasingly popularised (with extended meanings) in exoplanet science. In this talk, I will discuss why and how understanding the star-planet chemical connections is crucial to conduct quantitative comparative planetology towards understanding the interiors, surface and atmospheres of terrestrial-type exoplanets. For a preview of some aspects of the relevant work you may find this page useful
Thursday May 27, 10:30
Michele Trenti (University of Melbourne)
Colloquium: The SpIRIT mission: Multiwavelength detection and follow-up of cosmic explosions with an Australian space telescope
Observations of the transient sky to detect cosmic explosions critically rely on orbiting telescopes to cover the large range of wavelengths where atmospheric absorption and/or emission precludes the use of ground facilities. Thanks to dramatic technology improvements (Space 4.0), powerful miniaturised space telescopes operating as distributed-aperture constellations are offering new capabilities for high energy studies of transients to complement ageing existing satellites (Neil Gehrels Swift Observatory, Fermi GBM, INTEGRAL). With funding from the Australian Space Agency, the University of Melbourne is building SpIRIT, Australia's first space telescope, to be launched in 2022. SpIRIT is a gamma and x-ray nanosatellite that will operate as part of an international network of nanosatellites (the European High Energy Rapid Modular Ensemble of Satellites) for localisation of Gamma Ray Bursts (GRBs) and Gravitational Wave counterparts. Operations of an efficient X-ray all-sky-monitor with good localisation capability will have a pivotal role in the next decade on multi-messenger astrophysics, contributing to breakthrough discoveries in areas such as micro-second temporal structure of GRBs, their inner engines and jet composition. SpIRIT also has a strong link with the Australian space industry, and it aims to demonstrate new capabilities for on-board artificial intelligence and electric propulsion. In this talk, I will present an overview of the project, its current design and status, future plans, and highlight opportunities for collaboration.
Tuesday May 25, 15:00
Geray Karademir (CAS)
Student Review: MCR: Using clustering redshifts to measure galaxy luminosity functions

Time: May 25, 2021 02:00 PM Canberra, Melbourne, Sydney
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Thursday May 20, 10:30
Danny Price (ICRAR/Curtin)
Colloquium: A High-Speed All-Sky Monitor for Fast Radio Bursts and Technosignatures
Fast Radio Bursts (FRB) are one of the most intriguing transient phenomena discovered in the recent years, and recently observed down to 100-MHz frequencies. I will present the first southern hemisphere all-sky real-time imaging and radio-transient monitoring system, implemented on two prototype stations of the low frequency (50 - 350 MHz) component of the Square Kilometre Array (SKA-Low), the Engineering Development Array 2 (EDA2) and Aperture Array Verification System 2 (AAVS2). For the last two years these prototypes have been regularly collecting data to verify their performance against the SKA-Low specifications and simulations, including making all-sky images every two seconds used for transient searches. The transient identification algorithm used 2-second difference images to find candidates and required their detection in the images from both stations. In approximately 360 hours of data using a single coarse channel (0.926 MHz bandwidth), we identified a few episodes of extremely bright pulses from the pulsar PSR B0950+08 and several transients from an unknown object, which is currently under investigation. We also determined preliminary upper limits on surface density of radio transients at a 2-second timescale. We plan to increase the bandwidth by at least 40 times (to about 40 MHz) and time resolution to 10 ms or better in order to improve the sensitivity by two orders of magnitude and start detecting hundreds of FRBs per year. This upgrade will transform the stations into low-frequency FRB survey machines looking for FRBs and signals from extraterrestrial intelligence in high-resolution all-sky images, which will pave the way to similar searches with hundreds of SKA-Low station
Thursday May 6, 10:30
Tamara Davis (UQ)
Colloquium: The H0 Tension, searching for systematics
One of the biggest questions in cosmology right now is whether the disagreement in the values of the Hubble constant inferred from various probes is due to new fundamental physics or simply due to systematic errors in our measurements. The main disagreement is between low redshift standard candles like supernovae, and high redshift probes like the cosmic microwave background, with baryon acoustic oscillations, lensing, gravitational waves all also chipping in to the mix. Enormous amounts of effort have gone into determining whether the magnitudes of standard candles and distances to standard rules are correct and unbiased, but much less work has gone into determining whether the redshifts are unbiased. This talk will review the current status of the H0 tension, and look into the oft neglected redshift axis as a possible cause, while simultaneously pointing out a couple of common misconceptions about redshifts and velocities in the expanding universe.
Tuesday May 4, 10:30
Arianna Dolfi ()
Student Review: Assembly history of S0 galaxies
DTR review
Thursday Apr 29, 16:00
Dorottya Szecsi (Nicolaus Copernicus University & University of Cologne)
Colloquium: The role of metal-poor massive stars in galaxies near and far
Stellar feedback influences the structure and evolution of galaxies both near and far. Especially when it comes to massive stars, these objects are known to have a huge effect on their surroundings: they change the chemical composition of the gas around them via the stellar winds they eject, they explode as various energetic explosions like supernovae and gamma-ray bursts, and they leave remnants such as neutron stars and black holes, contributing to the dynamical evolution of the star-cluster or galaxy in question. What is more, these compact objects may merge and emit gravitational-wave signals for us to detect and follow up.

In this talk, I summarize what is currently known about massive stars – and in particular massive stars of metal-poor composition. These are the objects that were supposedly born in the first few generations of galaxies at cosmic ages, as well as those that may be present in local, low-metallicity dwarf galaxies, hidden in star-forming regions. Some of these stars can be directly associated with gravitational-wave emitting compact object mergers, at least from a theoretical point of view.

The field of metal-poor massive stars is actively and quickly developing these days. I will argue therefore that, while there has been many developments in recent years, one should expect new ones coming up, as more and more people turn their attention to these intriguing objects.
Tuesday Apr 27, 11:30
Ryan Turner ()
Student Review: Ryan Turner MCR
Thursday Apr 22, 10:30
Gemma Anderson (ICRAR)
Colloquium: Studying the explosive and transient sky with automated Australian radio telescopes
The Universe is an extremely dynamic place and for the most cataclysmic or fast events, the most interesting physics is occurring within the first seconds, minutes and days following its detection, motivating our need to be on-sky and observing a transient as soon as possible. I will describe the science driving my efforts to automate the Australia Telescope Compact Array (ATCA) and the Murchison Widefield Array (MWA). My research focuses on the rapid follow-up of short-duration gamma-ray bursts (GRBs), a known subclass of gravitational wave events that are well localised by the Swift telescope. ATCA can be on-target within 3 mins post-burst to probe the reverse shock emission from short GRBs, allowing us to determine a template of the radio luminosities and temporal behaviour of the gravitational wave events that will be detected by aLIGO/Virgo. As prompt radio emission becomes delayed with decreasing frequency due to dispersion, any prompt signals associated with transients may not arrive for seconds up to several minutes at MWA frequencies (80-300 MHz). The MWA automatic triggering response time of <20s is therefore fast enough to probe for the prompt FRB-like signals predicted to be produced by merging neutron star binaries (i.e. short GRBs). Employing image dedispersion techniques to search for prompt, coherent signals from short GRBs, we have placed strong limits on different merger models and scenarios, which will allow us to ultimately constrain different neutron star equations-of-state. While the MWA can be very quickly triggered, even the addition of dispersion delay does not make it possible for it to be on-target in time to detect a signal associated with an aLIGO/Virgo gravitational wave Superevent, which are only observed in the nearby Universe. However, I will describe how a combination of negative latency gravitational wave alerts and an unusual MWA configuration may make it possible to be on-target quick enough to search for associated prompt signals from a neutron star merger. Finally, I will discuss a new exciting collaboration between Curtin and Swinburne astronomers to study the low frequency components of FRBs by using the MWA to trigger on FRBs detected with UTMOST-2D.
Wednesday Apr 21, 10:30
Student Review: Brodie Norfolk's MCR
Tuesday Apr 20, 10:30
Christian Lehmann (CAS)
Student Review: Christian Lehmann's Mid-Candidature Review
This will be primarily an ***in-person*** review in the VR Theatre. Please physically come along!
Thursday Apr 1, 10:30
Elizabeth Mahony (CSIRO)
Colloquium: Early science results from the ASKAP-FLASH survey
Detections of the neutral hydrogen 21cm line in absorption can provide a powerful tool in understanding the role that cold gas plays in the formation and evolution of galaxies. The First Large Absorption-line Survey for HI (FLASH) takes advantage of the wide bandwidth, frequency range and radio-quiet site of the Australian Square Kilometre Array Pathfinder (ASKAP) telescope to search for HI out to redshifts of z=1, a parameter space which has been poorly explored until now. In this talk I will present an overview of the science case for the FLASH survey and show some early results obtained from pilot survey observations carried out last year.
Thursday Mar 25, 10:30
Anna Ho (UC Berkely)
Colloquium: The Landscape of Relativistic Stellar Explosions
For the last half-century, relativistic outflows accompanying the final collapse of massive stars have predominantly been detected via high-energy emission, as long-duration gamma-ray bursts (GRBs). From wide-field optical and radio time-domain surveys, there have been hints of related phenomena at lower energies, such as X-ray flashes. With the Zwicky Transient Facility (ZTF) we are conducting a systematic exploration of the broader landscape of engine-driven explosions, of which traditional GRBs are just one manifestation. The emerging zoo includes afterglows at cosmological distances with no detected GRB, broad-lined Ic (Ic-BL) supernovae with luminous X-ray and radio emission, and fast-luminous transients powered by circumstellar interaction such as AT2018cow. Understanding the origin of these events and their relation to GRBs will require coordinated observations between high-cadence optical surveys, wide-field gamma-ray monitors, and millimeter and radio observatories. This will be possible in the next few years with the launch of the Space-based multi-band astronomical Variable Objects Monitor (SVOM), the enhanced cadence of ZTF Phase II, and sensitive millimeter-band facilities like the Atacama Large Millimeter Array (ALMA).
Tuesday Mar 23, 10:30
Student Review: Student Review: Daniel McPherson
Thursday Mar 18, 10:30
Dougal Dobie (Swinburne)
Colloquium: Radio Follow-up of Gravitational Wave Events
The detection of gravitational waves and electromagnetic radiation from a neutron star merger, GW170817, heralded the dawn of a new age of astronomy - the multi-messenger era. In this talk, I will discuss follow-up of two landmark gravitational wave events - GW170817 and GW190814. Radio monitoring of GW170817 enabled tight constraints to be placed on the geometry and energetics of the merger, while VLBI imaging helped improve the "standard siren" measurement of the Hubble constant. No counterpart to GW190814 has been detected, but we have carried out 8 follow-up observations with ASKAP, covering ~90% of the localisation region. We have used these observations to carry out the most sensitive widefield radio transient survey to-date, and I will also present preliminary results from this search. I will outline prospects for radio follow-up of future gravitational wave events including the vital contributions that radio observations can make to the broader multi-messenger effort, and quantitative estimates for the detectability of events with current and future facilities.
Tuesday Mar 16, 10:30
Student Review: Student Review: Bron Reichardt Chu

Time: Mar 16, 2021 10:30 AM Australia/Melbourne
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Meeting ID: 846 4465 1795

Friday Mar 12, 10:30
Matt Miles (Swinburne)
Student Review: Matt Miles CoC
This is Matthew Miles's CoC presentation.
Tuesday Mar 9, 10:30
Stuart Lyall ()
Student Review: Stuart Lyall's CoC review
Thursday Mar 4, 10:30
Katie Grasha (ANU)
Colloquium: Stromlo stellar tracks: the importance of non-solar scaled abundances for massive stars
Our current understanding of galaxy evolution hinges on the assumption that the universe has Solar-scaled metallicity abundances, which is not applicable outside our Solar System. This prohibits progress in understanding how the distribution of the metals in stars are recycled into the interstellar gas of galaxies throughout cosmic time. In this talk, I will present the first set of massive stellar evolutionary models developed that are computed self-consistently in all the input parameters of the models. These models are based on physically realistic metal abundances in HII regions using the Galactic Concordance scaling system, which allows us, for the first time, for us to accurately compare stellar observations against models that are not constrained solely against a single star, the Sun. The evolutionary tracks for our Galactic Concordance abundance scaling provide a more physically motivated approach than simple uniform abundance scaling with metallicity for the analysis of HII regions and have considerable implications in determining nebular emission lines and metallicity. As the surface enhancement of elements in massive rotating stars have broad impact on the ionizing spectra of high-redshift, low-metallicity galaxies, such stellar models with realistic, variable metallicities need to be considered to accurately model and predict the properties of galaxies across cosmic time.
Tuesday Mar 2, 10:30
Sera Rauhut ()
Student Review: Sera Rauhut's CoC review
Friday Feb 26, 10:30
Aaron Myszka (Swinburne)
Student Review: Aaron Myszka CoC Review
Thursday Feb 25, 10:30
Ivo Seitenzahl (ADFA/UNSW Canberra)
Colloquium: From the remnant back to the supernova
Supernovae are explosive endpoints of stellar evolution. The most common two categories are core-collapse supernovae and thermonuclear supernovae. In core-collapse supernovae, the kinetic energy of the explosion is provided by the gravitational energy released when the iron core of an evolved massive star collapses to either a neutron star or a black hole. Open questions include how stripped supernovae lose their envelopes and which core-collapse supernovae make black holes and which make neutron stars. In part I of my talk, I will present examples of how optical integral field observations of the remnants of certain core-collapse supernovae, such as 1E0102.2-7219 or Puppis A, provide us with puzzling new structures that need to be understood if we want to make progress on the nature of their supernova progenitors.
In thermonuclear supernovae, the energy source is explosive nuclear fusion in white dwarf stars of lighter elements like helium, carbon, and oxygen, to heavier elements like silicon or nickel and iron. What kind of white dwarfs explode and how they evolve to ignition are still largely open questions.
In part II of my talk, I will present the recently discovered optical coronal line emission of the reverse shocked ejecta in three young thermonuclear supernova remnants and discuss a new approach to how these optical emission lines can be modelled to infer key parameters of the original supernova, such as explosion energy and mass.
Tuesday Feb 23, 10:30
Student Review: Student Review: Liyu Ambechew
Friday Feb 19, 10:30
Juan Espejo (Swinburne)
Student Review: Juan Espejo Mid Candidature review
Tuesday Feb 16, 10:30
Gurvarinder ()
Student Review: Gurvarinder's Mid-Candidature Review
Friday Feb 12, 10:30
Grace Lawrence ()
Student Review: Grace Lawrence MCR
Tuesday Feb 9, 10:30
Sara Webb ()
Student Review: Sara Webb's Draft Thesis Review