Skip to Content

Colloquia Series

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

Swinburne Virtual Reality Theatre
AR Building, Room 104
  2020    2019    2018    2017    2016    2015    2014    2013    2012    2011    2010    2009    2008    2007    2006    2005    2004    2003    2002    2001    2000   

2016 Colloquia

Thursday Dec 15, 11:30
Bernard Meade ()
Student Review: Mid-candidature revie
Tuesday Dec 13, 11:30
Alex Codoreanu ()
Student Review: Pre-submission review
Thursday Dec 8, 14:00
Dany Vohl ()
Student Review: Pre-submission review
Thursday Dec 8, 11:30
Anna Sippel (MPIA)
Colloquium: The impact of black holes on star cluster evolution
In the recent past, globular clusters have been suggested as the ideal environment to form stellar mass black hole binaries, which can tighten via interactions with other stars and evolve to become candidates for merging. By using a direct N-body model of a globular cluster I will illustrate this process and show that it doesn't go unnoticed for the cluster and its evolution.
Tuesday Dec 6, 10:30
Sarah Hegarty ()
Student Review: Mid-candidature review
Thursday Dec 1, 11:30
Benjamin Davis (Swinburne)
Colloquium: Spiral Arm Pitch Angle: Measurement and Relationship to Spiral Galaxy Structure and Supermassive Black Hole Mass
In this colloquium, I will discuss the geometric structure of spiral galaxies and how the visible structure can provide information about the central mass of a galaxy, the density of its galactic disk, and the hidden mass of the supermassive black hole in its nucleus. Logarithmic spirals are ubiquitous throughout nature, manifesting themselves as optimum rates of radial growth for azimuthal winding in numerous structures such as mollusk shells, tropical cyclones, and the arms of spiral galaxies. "Pitch angle" is a quantitative measurement describing the tightness of winding of logarithmic spirals. I will describe various methods for measuring the pitch angle for spiral galaxies. I will present a brief description of spiral density wave theory, which has been cited for approximately six decades as the agent for "grand design" spiral genesis in disk galaxies. I will provide observational evidence that pitch angle correlates well with the central mass and disk density of spiral galaxies, as predicted by spiral density wave theory. Finally, I will report recent work that further strengthens the usefulness of pitch angle as a predictor of the mass of supermassive black holes residing in spiral galaxies.
Tuesday Nov 29, 10:30
Frederic Robert (Swinburne University of Technology)
Student Review: Frederic Robert's confirmation review
Thursday Nov 24, 11:30
Jonathan Marshall (UNSW)
Colloquium: Using unresolved thermal emission to infer the presence of planets around disk-host stars
Debris disks -- tenuous rings of icy and rocky material produced by the breakup of asteroids and/or comets -- around main sequence stars are inferred to denote the presence of a planetary system. These disks are most commonly detected through the measurement of excess emission at infrared wavelengths from the host star. In most cases, the emission is spatially unresolved, so the radial extent of the disk is not precisely determined.
A simple relationship between stellar luminosity and disk extent has been determined based on a sample of known, resolved debris disks. This scaling can be applied to the vast majority of unresolved debris disks to identify systems that are larger than predicted from self-stirring models of disk evolution, from which the inference of perturbation by a planetary companion can be made.
Here I present an analysis of archival Spitzer and Herschel far-infrared observations covering a sample of over 100 debris disks, both resolved and unresolved, to identify those that are potentially in a phase of disk-planet interaction through migration.
Wednesday Nov 23, 11:30
Wael Farah (Swinburne University of Technology)
Student Review: Wael Farah Review

Wael's 6 month review.
Tuesday Nov 22, 11:30
Aditya Madapusi (Swinburne University of Technology)
Student Review: Aditya Review
Aditya 6 month review.
Friday Nov 18, 11:30
Samuel Hinton (University of Queensland)
Colloquium: Sounds Waves in Space: Measuring the 2D BAO signal in the WiggleZ survey
With increasing survey sizes, the strength of the statistical signal known as Baryon Acoustic Oscillations (BAO) are providing increasingly significant cosmological constraints on our Universe, helping us both to map out the evolutionary history of the cosmos, in addition to helping quantify the nature of dark matter and dark energy. I present results from the 2D anisotropic Baryon Acoustic Oscillation (BAO) signal present in the final dataset from the WiggleZ Dark Energy Survey, explaining the underlying model, and compare it to other cosmological probes from the Cosmic Microwave Background (CMB) and alternative BAO measurements. Within our survey's redshift bins and alternate methodologies of analysing the full correlation function vs reconstructing the BAO peak, we recover constraints between 5% and 22% error on matter density, angular diameter distance and Hubble's constant. Our cosmological constraints are consistent with Flat LambdaCDM cosmology and agree with results from the Baryon Oscillation Spectroscopic Survey (BOSS).
Tuesday Nov 15, 11:30
Bernard Meade ()
Student Review: Mid-candidature review
Tuesday Nov 15, 11:30
Caitlin Adams ()
Student Review: Caitlin Adams 18-month PhD review
Thursday Nov 10, 11:30
Prof. Keiichi Wada (Kagoshima University, Japan)
Colloquium: A new dynamical picture of structures of AGNs
For more than 20 years, a picture of AGNs has been widely accepted in the community, i.e. so called a "unified" model, which can simply explain spectral differences seen in nearby AGNs by changing viewing angles toward the obscured "torus" around the central source. We here propose that this "standard" picture should be reconsidered, based on our radiation hydrodynamic simulations of the ISM around AGNs. It is hard to keep a static "torus" around a central black hole. Instead, we found a more dynamic and natural solution: a radiation-driven fountain which can well explain the observational features of AGNs.
Tuesday Nov 8, 11:30
Stephanie Pointon (Swinburne)
Student Review: Stephanie Pointon's Confirmation Review
Thursday Nov 3, 11:30
Daniela Carollo (University of Notre Dame)
Colloquium: The Milky Way's Halo System: Ancient, Complex and a Storyteller of Galaxy Formation
The halo system of the Milky Way is a precious laboratory because it provides unique elemental abundances and kinematic information on the first objects formed in the Universe, and all this information can be used to tightly constrain models of galaxy formation and evolution. In this talk I will summarize the current view of the Galactic stellar halo, its architecture (diffuse components, structures), its age structure and the emerging chemical patterns (metallicity, CEMP stars). Possible formation scenarios of the Galaxy based on these results will be also discussed.
Thursday Oct 27, 11:30
Angela Garcia ()
Student Review: Angela Garcia pre-submission review talk
Thursday Oct 20, 11:30
Anna Ferre-Mateu (Swinburne)
Colloquium: The intriguing life of massive relic galaxies
Massive relic galaxies are the direct descendants of the massive and compact population at z~2, being a natural prediction of the LCDM cosmological model. In the now accepted two-phase model of formation and evolution depicted for massive galaxies, these galaxies are peculiar because they skip the merger-phase, remaining completely unchanged over cosmic time. Their stellar populations age but they remain as massive, compact and with the same morphologies they had at z~2: they remain frozen over cosmic time.
In this talk, I will first introduce the crusade followed to discover these relic galaxies in the local Universe and their implications for galaxy evolution theories. They are not only interesting because they open a direct window to the early Universe properties, but also because they show a myriad of intriguing properties that make them unique objects in the local Universe. For example, they seem to host ubermassive SMBHs, making them extreme outliers in the SMBH-galaxy local scaling relations. I will present an scenario that can explain the nature for such deviations, challenging the assumed universal co-evolution between SMBHs and their host galaxy.
Tuesday Oct 18, 11:30
Garry Foran (Swinbunrne)
Student Review: Garry Foran 6-month review
PhD 6-month review
Thursday Oct 13, 11:30
Katharina Lutz ()
Student Review: Katharina Lutz pre-submission review
Tuesday Oct 11, 11:30
Leonie ()
Student Review: Leonie's 6month review
6month review
Thursday Oct 6, 11:30
Paul Torrey (MIT/Caltech)
Colloquium: Lessons learned from modern large cosmological simulations
The past several years have seen the emergence a new generation of full volume cosmological hydrodynamical simulations aimed at studying the formation and evolution of galaxies. These simulations evolve large ~100 Mpc cubic volumes to redshift z=0, while resolving internal galaxy structure. I will describe the principal ingredients of one of these simulations, Illustris, report some of the most interesting and robust results to have emerged, and discuss areas where tension still exists with observations. Specifically, I will focus on: i) the feedback methods employed to shape the galaxy stellar mass function, ii) the emergence of morphological diversity among the resulting galaxy population, iii) the galaxy merger rate, and iv) implications for forging progenitor/descendant links in observed galaxy populations. I will end with a preview of expectations for the next generation of full volume cosmological simulations.
Tuesday Oct 4, 11:30
Sabine ()
Student Review: Sabine's 18month review
Thursday Sep 29, 11:30
Remco van den Bosch (MPIA)
Colloquium: Galaxies and their Super-Massive Black Holes
In galaxy evolution studies, the galaxies and their central super-massive black holes are commonly linked together through bulge growth scenario's. The evidence is the tight correlation between the black hole mass and the bulge mass in early-type galaxies. Surprisingly, the total mass of the galaxy does not correlate well with black holes mass. In this talk, I will show how black hole masses are measured with stellar kinematics. And I will show how the host galaxy properties correlate to black hole mass. Global processes appear to be most significant.
Tuesday Sep 27, 11:30
Igor Andreoni (Swinburne)
Student Review: Igor Andreoni 18-month review
18-month PhD review
Thursday Sep 15, 11:30
Michael Brown (Monash)
Colloquium: New calibrations of ultraviolet, mid-infrared and radio star formation rate indicators
As galaxies grow in stellar mass via galaxy mergers and star formation, accurate measurements of star formation rates are critical for understanding galaxy evolution. We present new calibrations of star formation rate indicators in the ultraviolet, mid-infrared and radio continuum bands, including the first direct calibration of 150 MHz as a star formation rate indicator. Our calibrations utilize up to 64 nearby star forming galaxies with Balmer decrement corrected H-alpha luminosities, and relative to the prior literature our sample spans a larger range of stellar mass and specific star formation rate. We have mitigated errors present in the prior literature, via the use of new imaging, improved calibrations of photometry and spectroscopy, new emission line measurements and matched aperture photometry. In some cases, we find star formation rates for dwarf galaxies derived from broadband photometry have to be revised upwards by an order of magnitude. We find 24 micron and 1.4 GHz radio continuum luminosities are tightly correlated with Balmer decrement corrected H-alpha luminosity, with the data having a scatter of just 0.2 dex around the best fit power-law. We find 150 MHz is a good star formation rate indicator, with relatively little scatter, which bodes well for MWA and LOFAR wide-field surveys.
Thursday Sep 1, 11:30
Shri Kulkarni (Caltech)
Colloquium: The Zwicky Transient Facility
The Zwicky Transient Facility (ZTF) has been designed with a singular focus: a systematic exploration of the night sky at a magnitude level well suited for spectral classification and follow up with the existing class of 4-m to 10-m class telescopes. ZTF is a public-private partnership with equal contributions from a consortium of world-wide partners and an NSF MSIP grant. The discovery engine for ZTF is a 47 square degree camera (realized through 16 e2V monolithic CCDs) that fills the entire focal plane of the 48-inch Oschin telescope of the Palomar Observatory. This clarity allows an exploration of different cadences and thus opens up the possibility for a thorough exploration of the dynamic optical sky. In short, ZTF is an experiment of Time Domain Astronomy (TDA) experiments.
ZTF consists of a 47 square degree camera on the Palomar Oschin 48-inch telescope (P48) and the Spectral Energy Distribution Machine (SEDM), a low resolution IFU spectrograph tuned for variability/transient classification, on the Palomar 60-inch telescope. The SEDM is already commissioned and the camera on P48 is expected to see first light in January 2017. At the short cadence end, ZTF will detect one young supernova (<1 day) every day. For mid-cadence we expect a veritable explosion of cosmic explosions. For long cadence, ZTF will be a prodigious factory for Tidal Disruption Events and Super-Luminous Supernovae. Visiting the Galactic Plane 300 times a year ZTF will be prove to be a bonanza for stellar astronomers. Since ZTF is PI-led effort there is considerable room for innovation and rapid implementation. In short, ZTF is a TDA pathfinder for LSST.
Tuesday Aug 30, 11:30
Student Review: Jacob Seiler 6 Month Review
Thursday Aug 18, 11:30
Themiya Nanayakkara (CAS)
Colloquium: In-situ IMF at z~2
The development of sensitive Near Infra-Red instruments has made it possible to study the galaxy properties at z~2, just 3Gy after the Big Bang. This is expected to be the time period where galaxies are actively star forming and evolving rapidly to form the massive galaxies that are observed in our local neighbourhood. ZFIRE is a survey, which utilises the MOSFIRE instrument on Keck telescope over 18 nights to study properties of ZFOURGE selected mass complete galaxies in rich environments at z~2.
In my talk I will present results of the first ever attempt to constrain the Initial Mass Function (IMF) of galaxies at these redshifts using a cluster and a field sample. We have investigated the degeneracy between the star formation histories and the IMF to make strong constrains on the stellar mass distribution of these galaxies using synthetic stellar spectra. I will focus on the role of dust, star-bursts, stellar rotation, binaries, and metallicity on determining observed galaxy properties at z~2 to address whether ZFIRE results favour the canonical concept of a universal IMF.
Thursday Aug 11, 11:30
Nobuo Arimoto (Subaru Observatory)
Colloquium: State of Subaru Observatory
This talk will provide an overview of current scientific capabilities and recent scientific highlights of Subaru Observatory. It will also look forward to forthcoming new instruments and the future roadmap of the observatory in the ELT era.
Thursday Aug 4, 11:30
Eric Howell (UWA)
Colloquium: Probing the violent Universe with gravitational wave astronomy
The first detection of gravitational waves (GWs) ranks as one of the major scientific and engineering achievements of this century. As the advanced GW detectors ramp up in sensitivity over the next few years, we can expect many more detections allowing us to use this new observational window to confront some of the outstanding questions in transient astronomy: what are the engines that drive cataclysmic transients, what are their histories and how are they connected. The most likely electromagnetic counterparts for GW transients are gamma-ray bursts (GRBs), the most luminous electromagnetic transients in the Universe. Although multi-wavelength observations over the last two decades have provided valuable insights into these bursts, there are still many outstanding questions regarding the emission mechanisms, the progenitors and the existence of different populations of burst. The opening of the GW domain can provide a path towards answering some of these questions.
In this talk I will provide brief introductory reviews on the rich history and current knowledge of gamma-ray bursts and on the status of ground based GW astronomy as we move towards the second advanced LIGO observation run later this year. I will then discuss the rich synergy between GRBs and GW transients and describe how multi-messenger astronomy can provide important insights into both phenomena over the remaining years of the advanced GW detector era and beyond.
Tuesday Aug 2, 11:30
Bogdan Ciambur (CAS)
Student Review: Student 18 month Review:
Abstract: TBA
Thursday Jul 28, 11:30
Jorge Cuadra (Universidad Catolica de Chile)
Colloquium: Gas dynamics and SMBH accretion in the Galactic centre
I will present numerical models of the gas dynamics in the inner parsec of the Galactic centre. We follow the gas from its origin as stellar winds of around 30 observed young massive stars, until it is either captured by the central black hole, or leaves the region. I will concentrate on two issues: the influence of the expected outflow from the inner accretion flow, and the creation of clumps that could explain the recently discovered cloud G2.
Thursday Jul 21, 11:30
Alastair Edge (Durham University)
Colloquium: The rise and fall (and rise again) of NGC1275
Recent observations have shown that the properties of the dens intracluster gas cooling in the cores of clusters of galaxies are significantly affected by AGN activity in the central brightest galaxy.
I will review these observations and focus on the most nearby example of this AGN Feedback from NGC1275 at the core of the Perseus cluster.
Tuesday Jul 19, 11:30
Srdan Kotus (Swinburne University of Technology)
Student Review: Student pre-submission review – Srdan Kotus
Thursday Jul 14, 11:30
Amandine Le Brun (CEA Saclay)
Colloquium: Galaxy clusters as cosmological probes and astrophysical laboratories
The existence of a hierarchy of cosmic structures, spanning a wide range of scales, has been unveiled by the astronomical observations of the last century. Galaxy clusters hold a special position within this hierarchy: they are the most massive objects that have formed according to the currently favoured hierarchical scenario of structure formation. In this scenario, small objects collapse first and later merge to form increasingly large ones. The new generation of cosmological surveys of galaxy clusters are now reaching the statistical precision needed to constrain the nature of the force driving the accelerated expansion of the Universe. However, they require an improvement of our understanding of cluster physics, especially of the physical processes of galaxy formation (which are now the limiting systematic uncertainty), and of non-linear structure formation, in order to make the constraints they place on cosmology more trustworthy. Any progress in that domain must stem from a confrontation between theoretical modelling, simulations and observations.
I will thus present cosmo-OWLS (Le Brun et al. 2014, McCarthy et al. 2014), the largest suite of ab initio cosmological hydrodynamical simulations ever carried out, and show that the models that invoke efficient AGN feedback reproduce a very wide range of properties of the local group/cluster population. I will then present an investigation of the scatter and evolution of the hot gas properties (as probed by X-ray and Sunyaev-Zel’dovich (SZ) observations) of galaxy groups and clusters as a function of the important non-gravitational physics of galaxy formation carried out using the same suite of simulations as well as the results of a study of the robustness of the some of the SZ stacking results reported by the Planck collaboration at the end of 2012 which was conducted using Sunyaev-Zel’dovich maps generated using a newly-developed multi-purpose lightcone software. Taken at face value, the Planck results seem to favour a close to self-similar relation between the SZ flux and total mass all the way down to individual galaxies, which is in contradiction with X-ray and absorption lines observations. Finally, I will present the first results of a new simulation campaign aimed at producing large cosmological simulations (1 Gpc/h on a side) of medium mass and spatial resolution and very-high resolution zoom simulations which are progressively including the non-gravitational physics of galaxy formation such as star formation, supernova and AGN feedback. These simulations are produced using the AMR code RAMSES and are being tailor-made to compare the evolution of the dark matter profiles of the most massive galaxy clusters since redshift 1 in simulations and observations.
Tuesday Jul 12, 11:30
Fabian Jankowski (CAS)
Student Review: Student 30-month review
Fabian's 30-month review on Molonglo and spectral and rotational properties of radio pulsars.
Thursday Jun 30, 11:30
Tiantian Yuan (ANU)
Colloquium: Disk Galaxy Assembly Across Cosmic Time: Combining Magnitude-limited Survey with Gravitational Lensing
One of the most compelling questions in current extragalactic astronomy is how galaxies in the early universe formed and evolved into those that we see today. To approach this problem, we need to construct a robust observational baseline for the star formation, mass assembly and chemical evolution history of galaxies. In this talk, I will summarize our near-infrared (NIR) spectroscopic surveys of galaxies at intermediate and high redshifts. By combining the global properties of galaxies from magnitude-limited surveys and the spatially resolved properties from gravitationally lensed galaxies, we have obtained crucial insights into the basic problems of galaxy formation and evolution such as the origin of the metallicity gradient, the formation of the spiral arms and the role of the large-scale clustering environment.
Thursday Jun 16, 11:30
Stas Shabala (University of Tasmania)
Colloquium: Unlocking the physics of radio galaxies and AGN feedback
Active Galactic Nuclei (AGN) play a key role in the formation and evolution of galaxies through so-called AGN feedback. Quantifying the magnitude (and even the sign) of this feedback, however, is difficult. Two parameters play a key role in determining feedback efficiency: (1) the kinetic power of AGN jets, which set how much energy is available for feedback; and (2) the timescales related to their injection, which determine the efficiency with which this energy is deposited in the surrounding gas.
I will briefly discuss different ways of inferring the physical properties of AGN jets. A popular method of measuring jet kinetic power involves using the energetics of X-ray deficient radio bubbles; our recent work (Godfrey & Shabala 2016) shows that this approach in fact suffers strongly from selection effects, and does not provide a good measure of jet power. I will outline a recent approach (Turner & Shabala 2015) in which we combine models describing the dynamical evolution of observable radio AGN properties with semi-analytic galaxy formation models. This technique can be used to derive the physical properties of low-redshift AGN, shedding light on processes driving AGN triggering and feedback. I will also briefly describe the complementary numerical simulations currently being developed by our group, and the synergy between our models and large multi-wavelength data sets.
Tuesday Jun 14, 11:00
Toby Brown ()
Student Review: 30 Month Review
Thursday Jun 9, 11:30
Vikram Ravi (Caltech)
Colloquium: Do fast radio bursts originate at cosmological distances?
Extragalactic fast radio bursts (FRBs) are now established as a bona fide astrophysical phenomenon. Although FRBs are among the brightest radio point-sources in the sky during their brief (< few millisecond) durations, and between 2000 and 10,000 occur each day, more theories are currently proposed for their progenitors than there are recorded events. There is no more exciting time to be involved in a field! I will address the question of the FRB distance scale. Although the amounts by which FRBs are dispersed indicate cosmological origins (redshifts ~ 0.2 - 2), substantial plasma column densities may be contributed by FRB host galaxies. Additionally, no firm correlations exist between possibly distance-dependent FRB properties (such as flux densities and amounts of scattering) and FRB dispersion measures. However, I will present new analyses that suggest that the FRB population is consistent with a cosmological origin, and inconsistent with a local-Universe origin. If FRBs are cosmological, substantial insight may be gained into the baryon and magnetic-field distributions on cosmological scales.
Thursday Jun 2, 11:30
Vivek Venkatraman Krishnan (CAS)
Student Review: Vivek Venkatraman Krishnan 18 month review
Vivek's 18 month review on his PhD on Molonglo, MeerKAT and the relativistic pulsar J1141-6545.
Wednesday Jun 1, 11:30
Jonathan Horner (University of Southern Queensland)
Colloquium: Exoplanets, Dynamics, and the search for life elsewhere...
In the past few years, the number of planets discovered orbiting other stars has grown dramatically, and newly discovered planets are now announced on an almost daily basis. In this talk, I will describe how simulations of the orbital evolution of such planets can help us to better constrain their orbits, and even allow us to identify systems that are not all they seem to be. In addition, in coming years it is likely that the first truly Earth-like exoplanets will be discovered, and I will describe how those same dynamical tools will prove vital in assessing which of those planets are the most promising targets in the search for life beyond the Solar system.
Tuesday May 31, 11:30
Luca Rossi (Swinburne)
Student Review: Luca Rossi 30 month review
Thursday May 26, 11:30
Manodeep Sinha (CAS)
Colloquium: Accurate Modeling of Galaxy Clustering on Small Scales: Testing the Standard ΛCDM + Halo Model
The large-scale distribution of galaxies can be explained fairly simply by assuming i) all galaxies are hosted by halos and ii) a cosmological model. This simple framework, called the 'halo-model', has been remarkably successful at reproducing the large-scale clustering of galaxies observed in various galaxy redshift surveys. However, none of these studies have truly tested the 'halo-model' by carefully modeling the systematics. We present the results from a fully-numerical, accurate 'halo-model' framework and show that the theory can not simultaneously reproduce the galaxy projected correlation function and the group multiplicity function in the SDSS main samples. In particular, the bright galaxy sample shows significant tension with theory. We discuss the implications of our findings, as well as how to constrain different aspects of galaxy formation by simultaneously fitting multiple statistics.
Tuesday May 24, 11:30
Busola Alabi ()
Student Review: 30month review
Thursday May 19, 11:30
Ian Morrison (Swinburne)
Colloquium: Constraining the SETI discovery space
Even with the welcome influx of funds from Breakthrough Listen, SETI does not have the resources for a continuous and comprehensive search of the whole sky, across all frequency bands, for all potential signal types. I will describe efforts to scientifically constrain the discovery space in each of these search dimensions. I will explain why SETI should concern itself with wideband signals, discuss the challenges in doing so, and describe one promising new search algorithm being trialled by both the SETI Institute and Breakthrough Listen.
Tuesday May 10, 11:30
Chris Curtin (Swinburne)
Student Review: 18-month review
18-month PhD review
Thursday May 5, 11:30
Evan Keane (The University of Manchester Jodrell Bank Observatory)
Colloquium: Fast Radio Bursts & SUPERB
In this talk I will summarise the many developments that have occurred in fast radio burst science in the last year. I will describe the SUPERB survey, and its latest discoveries of FRBs and pulsars. I will review the current status of the global FRB search effort and their abilities to localise and follow-up events, as well as looking forward to the prospects over the coming few years, where progress in this exciting field is expected to be ever more rapid.
Thursday Apr 28, 11:30
Jon Clarke (Mars Society Australia)
Colloquium: Searching for life on early Mars: lessons from the Pilbara
Stromatolites are readily identified, outcrop scale indicators of potential biological activity, even though constructed by microbes. Their presence in ~3.5 Ga volcano-sedimentary successions of the Pilbara region of Western Australia suggests that they might also occur in similar, Noachian-age successions On Mars. Field and basic laboratory studies of one such occurrence near Nullagine highlight many issues that would be faced by any stromatolite search strategy on Mars. Firstly, the stromatolites are found in local aggregations that make up a very small part of the overall succession, possibly as little as one millionth of the outcrop area. An effective search strategy would require a combination of remote sensing to highlight features with high probability of hosting stromatolites, precision landing, and extensive cross-country mobility, difficult to achieve with a purely unmanned exploration system. Secondly, the limited analytical suite available to any unmanned mission would make conclusive determination of thc biogenicity of any stromatolite-like feature on Mars very difficult. This is shown by the controversy over the biogenicity of the Pilbara examples, despite a much greater range of analytical techniques applied to the Pilbara examples. Thirdly, the low rate of data assessment with unmanned missions results in possible biogenic features being identified long after they can be be further studied. Once possible stromatolites features have been found on Mars, sample return would be imperative to determine their biogenicity, preferably supported by on ground field work by astronaut-scientists.
Tuesday Apr 26, 11:00
Shivani Bhandari ()
Student Review: Shivani's 18-month review
Thursday Apr 21, 11:30
Michelle Cluver (University of Cape Town)
Colloquium: Star Formation and the Battle of the Bulge
The evolution of a galaxy from a coalescence of neutral gas, to the diverse array of galaxy specimens we observe today, appears to be a complex amalgamation of factors and mechanisms acting on large and small scales. The effects of tidal interactions and close encounters in groups of galaxies is not yet well-understood, but incorporates some very interesting physics with potentially broad implications for galaxy evolution modelling. In this talk I will discuss how WISE mid-infrared data, in conjunction with multiwavelength information from GAMA, can be used to study stellar mass build-up and star formation. In addition, pilot results and plans for an HI-study using the sensitive MeerKAT SKA Pathfinder.
Tuesday Apr 19, 11:30
Matt Agnew ()
Student Review: Matt Agnew's 6 month review
Tuesday Apr 12, 11:30
Andreas Burkert (Ludwig Maximilians University, Munich)
Colloquium: The origin and dynamics of high-redshift disk galaxies
The redshift two Universe ist one of the most interesting epochs of galaxy evolution. It is the era with the peak of the cosmic star formation rate. Between redshift 3 and 1 the total stellar mass density in galaxies increased from 15% to 70%. It is also the time of rapid galaxy assembly and the epoch where galaxy morphology was determined.
I will summarize recent observations of the SINS survey, a Spectroscopic Imaging survey of z=2 galaxies in the near infrared with SINFONI. This survey has opened a fascinating window into early galaxy evolution. The SINS data show a diversity of galactic systems at redshift 2 with physical properties that are unparalleled in the z=0 Universe. Gas-rich, extended, fast rotating and highly turbulent disks have been found with star formation rates that are a factor of 10 to 100 larger than in present-day Milky-Way type galaxies. Kpc-sized, massive gas clumps dominate the appearance of these galaxies. These giant clumps are considered to represent the progenitors of present-day globular clusters. They could provide the seeds for supermassive black holes and they might lead to the formation of young bulges in the centers of their galaxies.
These fascinating and puzzling observations will be confronted with theoretical ideas and numerical simulations of gas-rich galactic disk evolution (Behrendt et al. 15, 16). I will argue that the high-redshift galaxies, like present-day disks, are in a self-organized equilibrium state with their observed extreme
properties emerging naturally from self-regulated galactic evolution, controlled by gas inflow from the
cosmic web.
Thursday Apr 7, 11:30
Brett Carter (RMIT)
Colloquium: Space weather and its influence on modern-day technologies: Extreme events are not the be-all and end-all
The near-Earth space environment can be broken up into four distinct, but strongly coupled, regions; the Sun, the solar wind, the Earth’s magnetosphere and the Earth’s ionosphere. The term “space weather” is used to describe the state of this Sun-to-Earth system in terms of the plasma within it, and is often governed by processes originating at the Sun; e.g., coronal mass ejections (CMEs) and high-speed solar wind streams.
Extreme space weather (e.g., caused by CMEs) poses a significant risk to modern technological infrastructure located on the ground (e.g., electrical power grids) and in space (e.g., navigation and telecommunications spacecraft). However, recent research has revealed that adverse space weather effects are not only limited to severe space weather events or “geomagnetic storms”. Accurate positioning and timing using Global Navigation Satellite Systems (GNSS) is a good example of a heavily relied-upon space-based technology that can be significantly affected during quiet geomagnetic conditions. Recently, it has also been shown that significant power grid fluctuations, which can influence wholesale electricity markets, can occur during what would normally be classified as “quiet” conditions.
The Earth’s ionosphere, which is located between 80 km and 1000 km altitude, is home to a number of intrinsic phenomena that cause problems on various technological systems, in addition to the disturbances that originate at the Sun’s surface. In this presentation, an overview of space weather will be given, followed by a historical overview of severe space weather events and their reported effects. Then, the quiet-time ionospheric processes that influence the use of GNSS will be introduced and explored, including some recent developments. Finally, a discussion will be given about the gaps in knowledge that are currently hampering the development of real-time space weather predictions that would benefit our communications networks where the signals traverse the ionosphere.
Thursday Mar 31, 11:30
Chiara Tonini (The University of Melbourne)
Colloquium: The growth of disks and bulges during hierarchical galaxy formation: fast evolution vs secular processes
I present a theoretical model for the evolution of mass, angular momentum and size of galaxy disks and bulges, and we implement it into the semi-analytic galaxy formation code SAGE. The model follows both secular and violent evolutionary channels, including smooth accretion, disk instabilities, minor and major mergers.
We find that the combination of our recipe with hierarchical clustering produces two distinct populations of bulges: merger-driven bulges, akin to classical bulges and ellipticals, and instability-driven bulges, akin to secular (or pseudo-)bulges.
Through the present implementation the mass accretion history is perceivable in the galaxy structure, morphology and colours.
Thursday Mar 24, 11:30
Benedetta Vulcani (Melbourne University)
Colloquium: How star formation is shut down depends on environment, but the properties of galaxies in transition do not
What physical processes regulate star formation in dense environments? Understanding why galaxy evolution is environment dependent is one of the key questions of current astrophysics. I will present an analysis of those galaxies that show signs of an ongoing or recent transformation of their star formation activity and/or morphology discussing an evolutionary scenario that links all the different populations at z=0. I will focus my attention on the SFR-mass relation in the different environments, showing how the star formation is suppressed in clusters with respect to the field, both a t z=0 and at z=0.5. Finally, I will present the first characterization of the spatial distribution of star formation in cluster galaxies at z~0.5, and compare to a field control sample, in order to quantify the role of different physical processes that are believed to be responsible for shutting down star formation.
Tuesday Mar 22, 11:30
M Durre (Swinburne)
Student Review: Mark Durre 30 month review
30 month review PhD thesis
Thursday Mar 17, 11:30
Danail Obreschkow (UWA)
Colloquium: Angular Momentum at the Heart of Galaxy Morphologies?
Since the time of Kant it has been supposed that angular momentum (AM) was fundamental to the nature of the ‘spiral nebulae’, now known as galaxies. A century after the first measurement of galaxy rotations,
theoretical and observational tools are now mature for systematic analyses of galaxy AM. This colloquium will commence by recalling the expected role of AM in shaping galaxies, and successively highlight recent progress in understanding the detailed relationship between AM and galactic substructure. First, I will highlight the mass-spin-morphology relation of spiral galaxies, as seen in the THINGS survey. Then, the view will be expanded to a larger class of objects, including ellipticals, dwarfs, and clumpy disks. I will report on the first precision AM measurements in a sample of rare local clumpy disks, which appear to be remarkably similar to main-sequence turbulent disks at redshift z=1-2. We found that these clumpy objects have a factor three less AM and a factor three more cold gas than typical nearby spiral galaxies. An analytical analysis reveals that low AM is the main reason for the low disk stability and hence increased star-formation efficiency, while the higher gas fraction plays a secondary role. This result contrasts with the common belief that high gas fractions are the main reason for clumpy, turbulent morphologies. We will carefully discuss this important result, by showing its limitations and highlighting its potential to revolutionise our views on galaxy evolution in a cosmological context.
Thursday Mar 10, 11:30
John Peacock (University of Edinburgh)
Colloquium: Gravitational lensing of the Cosmic Microwave Background: flux conservation and growth of inhomogeneities
Gravitational lensing is a rich source of cosmological information: it probes both the amplitude and evolution of metric fluctuations, plus the distance-redshift relation via the geometry of the distortion of background images. But in 2014, Clarkson et al. suggested that lensing had an average non-Newtonian "back-reaction" effect, which altered the effective distance to the CMB last-scattering surface, potentially by several percent - enough to cause substantial change in the cosmological parameters we infer. The
first part of this talk discusses this issue from the point of view of flux conservation theorems due to Weinberg and to Kibble & Lieu, and a possible loophole in these theorems is identified. This loophole
relates to the area of constant-redshift surfaces, and the solution to this puzzle is critical in order to decide whether the Clarkson et al. claims should be taken seriously. The second part of the talk presents some new results on cross-correlation between galaxy surveys (based on WISE & SuperCOSMOS) and CMB lensing data. These yield interesting measurements of the evolution of cosmological perturbations at
redshift z<0.35.
Thursday Mar 3, 11:30
Luke Davies (UWA)
Colloquium: Star-formation, Mergers and the Assembly of Stellar Mass in Galaxies
Since the first stars and then galaxies formed the Universe has been an immense factory converting neutral gas into stellar material. The distribution of this stellar material is key to our understanding of galaxy formation and evolution as it is the primary baryonic component we can observe in galaxies over the last 13Gyr. However, the changing distribution of stars at a given epoch is dependant on many different processes such as: i) in-situ star-formation rates, ii) merger rates, iii) the neutral gas reservoirs available for future star-formation episodes, iv) the effect of galaxy-galaxy interactions on both star-formation and neutral gas content and v) AGN activity. These processes occur in different measures to all galaxies over the history of the Universe, ultimately resulting in the distribution of stellar material we see today. If we wish to understand the assembly of stellar mass in the Universe we must aim to probe all of these process, and build a complete and consistent picture of their interplay over cosmic timescales.
In this seminar I will discuss recent results from the Galaxy And Mass Assembly (GAMA) survey, probing the assembly of stellar mass though both in-situ star formation (as traced by multiple SFR indicators) and interactions (both mergers and interaction induced star-formation) - in galaxies spanning ~4 decades in stellar mass. I will discuss upcoming HI surveys which are aligned with the current state-of-the-art multi-wavelength, spectroscopic surveys - allowing us to simultaneous probe both star-formation and neutral gas reservoirs in a consistent and statistically robust sample of galaxies. Lastly, I will discuss how large area surveys of the coming decade, such as the Wide Area VISTA Extragalactic Survey (WAVES), will help revolutionise our understanding of the assembly of stellar mass is galaxies.
Thursday Feb 25, 11:30
James Wurster (Monash)
Colloquium: On the formation of discs using non-ideal magnetohydrodynamics
Discs are observed to form around young stars. However, discs have historically failed to form in numerical simulations of star formation; this is known as the magnetic braking catastrophe. One possible solution is the inclusion of non-ideal magnetohydrodynamics (MHD). I will discuss the three non-ideal MHD processes and examine impact that they have on star formation. There will be a focus on the Hall effect, since recent studies indicate that this is the dominate term in determining whether a disc forms or not.
Thursday Feb 18, 16:00
Grace, Konner and Josh (Swinburne University undergrad)
Student Review: R&D1 Presentations
Final talks from our R&D undergraduates who have spent the last 6 weeks working on a variety of topics in CAS.

Grace Lawrence will speak about direct dark matter detection with SABRE, the world’s first such
facility in the southern hemisphere.

Konner Blunt will speak about the Mission to Mars and the challenges of actually getting to the
red planet safely and cost-effectively.

Joshua Minter will then speak about whether the newly landed Martian will actually survive and
perhaps thrive by growing crops and building on Mars.
Thursday Feb 18, 11:30
Paul Lasky (Monash)
Colloquium: The dawn of gravitational-wave astronomy
LIGO has directly detected gravitational waves. The inspiral, merger and ringdown of two black holes was measured on the 14th of September 2015. I will describe in detail the experiment, the observations and the future of gravitational-wave astronomy.
Thursday Feb 4, 11:30
Mark Krumholz (ANU)
Colloquium: Fuelling Star Formation Across Cosmic Time
At the present cosmic epoch, only the most massive galaxies appear to have ceased active star formation. For the remainder, sustaining star formation requires an adequate supply of interstellar gas, and it is far from clear where this gas comes from. While there is enough gas in the intergalactic medium to provide a continuing fuel supply, it is unlikely to fall onto the centres of galaxies where star formation is expected to be quenched most rapidly. Nor does infall of intergalactic gas naturally explain the pattern of star formation seen in dwarf galaxies, which have extraordinarily large gas fractions. In this talk I argue that, by combining novel mechanisms for regulating star formation with an understanding of how gas is transported through galaxies, we can understand the pattern of which galaxies form stars at what rates, and where within those galaxies star formation takes place.
Thursday Jan 28, 11:30
Sheila Kannappan (University of North Carolina)
Colloquium: The REsolved Spectroscopy Of a Local VolumE (RESOLVE) Survey and its Environmental COntext (ECO) Catalog
The RESOLVE survey is a volume-limited census of stellar, gas, and dynamical mass as well as star formation and galaxy interactions within >50,000 cubic Mpc of the z~0 cosmic web, reaching down to dwarf galaxies of baryonic mass ~10^9 Msun and up to large-scale groups/clusters, filaments, walls, and voids. RESOLVE is surrounded by the ~10x larger ECO catalog, which uses matched environment metrics and photometric pipelines. RESOLVE/ECO photometry improves dramatically on standard pipeline photometry through careful treatment of sky subtraction, color gradients, and flux extrapolation, with important implications for galaxy star formation histories. ECO offers greater statistical power for analysis of cosmic variance, while RESOLVE offers superior redshift completeness, complete and deep 21cm data probing gas content down to 5-10% of stellar mass, and a growing inventory of 3D optical spectroscopy. I will present early results drawing on recent and upcoming RESOLVE/ECO data releases, for example revealing environment-dependent substructure in the baryonic mass function plausibly tied to group formation, signs of fresh gas accretion and rapid stellar and baryonic mass growth in low-mass
halos, and gas deficiency in dwarfs within or near intermediate-mass halos down to 10^12 Msun as well as in large-scale cosmic walls.