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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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2017 Colloquia

Thursday Dec 14, 10:30
Student Review: Colin Jacobs - Mid-candidature review
Tuesday Dec 12, 10:30
Vardha Bennert (California Polytechnic State University, USA)
Colloquium: The Origin of the Black Hole Mass Scaling Relations
The discovery of close correlations between supermassive BHs and their host-galaxy properties has sparked a flood of observational studies pertaining both to the local Universe and cosmic history over the last decade. Nevertheless, a clear understanding of their origin still eludes us. Uncertainty remains as to the fundamental driver of these relations, whether purely local and baryonic or global and dark matter dominated. While studying the evolution of these relations with cosmic time provides valuable clues, a definitive resolution of this conundrum relies on understanding slope and scatter of local relations for AGNs. We discuss results from a unique three-fold approach. (i) From a sample of ~100 AGNs in the local Universe, we build a robust baseline of the BH mass scaling relations (MBH-sigma, MBH-L, MBH-M), combining spatially-resolved Keck spectroscopy with SDSS imaging. (ii) We study the evolution of the MBH-sigma and MBH-L relations out to a look-back time of 4-6 Gyrs using Keck spectra and HST images. (iii) We extend this study out to the pivotal cosmic time between the peak of AGN activity and the establishment of the present-day Hubble sequence, a look-back time of 8-10 Gyrs. We measure spheroid stellar masses using deep multi-color HST images from GOODS and determine the MBH-M relation. The results (i) indicate that AGNs follow the same scaling relations as inactive galaxies. From (ii-iii) we conclude that BH growth precedes bulge assembly. Combining results from (i-iii) allows us to test the hypothesis that evolution is driven by disks being transformed into bulges.
Thursday Dec 7, 10:30
Bernhard Mueller (Monash)
Colloquium: Unravelling the mysteries of exploding massive stars
Core-collapse supernovae, the explosions of massive stars, have remained one of the outstanding challenges in computational astrophysics for decades, and the mechanism by which they explode has long eluded us. Recently, however, it has become possible to perform 3D radiation hydrodynamics simulations, and there is a growing body of models that develop successful explosions. One of the main challenges is now to corroborate the simulations by confronting them with observables. In this talk I shall outline to what extent the models make predictions that can be tested by current and future observations. Multi-dimensional simulations have already furnished quite mature predictions for gravitational wave (GW) and neutrino signals, whose diagnostic power would be considerable in the event of a Galactic supernova, especially for a nearby event and with 3rd generation GW detectors. In the most optimistic case, one could obtain time-dependent measurements of neutron star and shock parameters. Predicting other observational signatures, such as light curves and spectra, remains a bigger challenge for first-principle models. Nonetheless there is progress on this front as well thanks to the advent of multi-dimensional long-time simulations that now seem broadly compatible with observed neutron star birth properties.
Tuesday Dec 5, 10:30
Fred Robert (Swinburne University of Technology)
Student Review: Fred Robert's mid-candidature review
Thursday Nov 30, 10:30
Geoff Bryan ()
Student Review: Geoff Bryan's 6 month review
Tuesday Nov 28, 10:30
Chandra Murugeshan ()
Student Review: 6-month review
Friday Nov 24, 14:00
Ewine F. van Dishoeck (Leiden Observatory, The Netherlands / MPE Garching)
Colloquium: Zooming in on planet-forming zones of disks around young stars
Protoplanetary disks are the birthplaces of planets but the spatial resolution at long wavelengths has so far been insufficient to resolve the critical 5-30 AU region. The Atacama Large Millimeter Array (ALMA) now allows us to zoom in to nearby disks and determine the physical and chemical structure associated with planet formation. This talk will provide examples of recent work on observations and models of protoplanetary disks in various stages of evolution. Surveys of large numbers of disks provide insight into typical masses and sizes, revealing surprisingly weak gas emission.
Special attention will be given to transitional disks, which are a subset of disks with evidence for sharp-rimmed cavities (gaps or holes). They are the best candidate sources for harboring just-formed giant planets. ALMA allows imaging of both the gas and dust in these disks, providing constraints on the properties of any young planets. Some prospects for JWST will be mentioned.
Thursday Nov 16, 10:30
James Wadsley (McMaster University)
Colloquium: Superbubbles and the limits of Supernovae on Galactic Scales
The theme of the talk is how different modes of stellar feedback affect the evolution of galaxies and how, with appropriate care, we can constrain the role of the historically popular supernova feedback on the evolution of galaxies and their stellar content. We argue that prior work has modeled supernovae poorly by ignoring stellar clusters and also the key physics of conduction that governs hot gas evolution. Clustered supernovae create superbubbles, kpc scale feedback events that can drive strong galactic winds. We show that superbubbles can be modeled via first principles simulations without resorting to common numerical tricks. Galaxies with superbubble feedback strongly regulate their star formation and global baryon budget. These simulated galaxies match disk galaxy observations very well. However, there are limits -- supernovae cannot explain the regulation of star formation in all galaxies.
Wednesday Nov 15, 13:30
Wael Farah ()
Student Review: Wael Farah- 18 month review
Wael Farah 18 month PhD review
Friday Nov 10, 10:30
Chiaki Kobayashi (University of Hertfordshire, UK)
Colloquium: Elemental Abundances across Cosmic Time
Thanks to nuclear astro-physics collaboration, we now have good understanding of the origin of elements from carbon to zinc, and theoretical models have well reproduced the observations of these elemental abundances in the Milky Way Galaxy. Now we can constrain galaxy formation processes such as supernova and AGN feedback using metallicities and elemental abundances. Our cosmological simulations are in good agreement with many observations, namely, mass-metallicity relations of galaxies (which evolve with a steeper slope at higher redshifts) and metallicity radial gradients within galaxies (which can trace the merging history of the galaxies). Stellar [alpha/Fe] ratios of early-type galaxies become closer to observations with AGN feedback (where the seed blackholes originate the first stars). The gas-phase C, N and O abundances can constrain the star formation history of disk galaxies, which can be used for future observations with JWST. Using our cosmological simulations, we also predict the cosmic supernovae rates for various types such as Type Iax and super-luminous supernovae.
Thursday Nov 9, 10:30
Frederic Vogt (European Southern Observatory)
Colloquium: What lies in the more! The MUSE view of SNR E0102 in the SMC
1E0102.2-7219 (E0102 for short) is one of the handful of known oxygen-dominated, young supernova remnants. These systems, caught only a few 1000 years after the SN explosion of a massive star, display fast moving (a few 1000 km/s), oxygen-bright, hydrogen-poor filaments visible at optical wavelengths: the outer-layers of the progenitor star, expelled during the SN explosion, and (still) expanding ballistically. In this talk, I will present recent observations of E0102 with the MUSE optical integral field spectrograph at the VLT. I will describe both the original motivation for these observations - namely the first detection of Sulfur lines from the fast ejecta with the WiFeS integral field spectrograph - as well as the exciting and unanticipated discoveries that were found lurking in the MUSE datacube.
Thursday Nov 2, 10:30
Garry Foran ()
Student Review: Garry Foran 18-month review
Garry Foran's 18-month review
Thursday Oct 26, 10:30
Daniel Price (Monash University)
Colloquium: Are we witnessing the birth of planets?
In the last few years, new telescopes including the Atacama Large Millimetre/Submillimetre Array and extreme adaptive optics on the Very Large Telescope (VLT) have given us amazing new pictures of the swirling discs of gas and dust around young stars, known as protoplanetary discs. These pictures are revolutionising our ideas about how planets are born. I will discuss our attempts to use computer modelling of star and planet formation to understand the new images, what we have learnt so far, and I will make some controversial suggestions.
Tuesday Oct 24, 10:30
Leonie Chevalier ()
Student Review: Leonie Chevalier 18-Month Review
Thursday Oct 19, 10:30
Tom Collett (ICG, Portsmouth)
Colloquium: Cosmology with Strong Gravitational Lensing
Local measurements of the expansion rate are in tension with those inferred from observations of the distant Universe. Is this the first sign of new physics or merely a sign of systematic errors within individual probes? This key question remains unsolved, because there are only a handful of established probes. Here I will talk about how strong gravitational lensing offers a new window on precision cosmology, shining a new light on the dark Universe.

I will present strong lensing constraints on the expansion rate of the Universe and the equation of state of dark energy. I will also show how lensing combined with stellar dynamics yields the most precise test to date of the validity of General Relativity on extragalactic scales.
Tuesday Oct 17, 10:30
Stephanie Pointon (Swinburne)
Student Review: Stephanie Pointon - Mid-candidature Review
Tuesday Oct 10, 13:30
Igor Andreoni (Swinburne)
Student Review: Igor Andeoni Pre-submission review
PhD 30-month (pre-submission) review. Note later time than usual.
Thursday Oct 5, 10:30
Angela Garcia (Swinburne)
Colloquium: HI and metal absorption lines during the Epoch of Reionization
In this work, we study the epoch of Reionization (EoR) with metal absorption lines in quasar spectra at high redshift, using high resolution hydrodynamical simulations (an improved version of GADGET-3). For this purpose, we set up the physical conditions of the intergalactic medium (IGM) at z_{EoR}, and we post-process the simulations to implement a uniform UV ionizing background for quasars and galaxies (Haardt-Madau 2012), the metal ions with CLOUDY 8.1 and HI self-shielding prescription (Rahmati et al. 2013). We use Voigt profile fitting to compute the column densities of the ions from the synthetic spectra and obtain a statistical distribution of the absorbers. This procedure allows us to study the evolution of the state of the IGM at high redshift, compute the cosmological mass density of CIV and HI and other ions. Our simulations produce absorber properties that are in good agreement with observations in the literature, especially for the high ionization species.
Furthermore, we are able to reproduce an observed example of an LAE galaxy-CIV absorber pair at z=5.7, proving a physical insight into such systems beyond the limit of current observations. Finally, we vary of the uniform UVB at z~6, and compare directly with observations of different metal ions, in order to constrain the ionizing background at the tail of Reionization.
Tuesday Oct 3, 10:30
Sabine Bellstedt ()
Student Review: 30 Month Review - Sabine Bellstedt
Wednesday Sep 20, 10:30
The ESO Director for Science Dr Rob Ivison, and the Head of the (ESO)
Colloquium: ESO Roadshow
Following the signing of the Strategic Partnership agreement between the European Southern Observatory (ESO) and the Australian government on 11 July 2017, Australian-based astronomers will be eligible to apply for observing time on the facilities of the La Silla Paranal Observatories in Chile commencing with Period 101 (1 April - 30 Sep 2018). The Call for Proposals will be issued at the end of August, and the proposal deadline will be Thursday 28 September 2017.

In the lead up to this proposal round the AAO's International Telescopes Support Office (ITSO) is coordinating a series of "ESO Community Days" around Australia, on behalf of ESO, the Department of Industry, Innovation and Science, and Astronomy Australia Ltd. The ESO Director for Science Dr Rob Ivison, and the Head of the Observing Programs Office at ESO Dr Ferdinando Patat, will provide a comprehensive overview of the current and future observing facilities available, as well as the proposal preparation, submission, and assessment process. The sessions will run from 10am until lunchtime as follows:

Monday 18 Sep 2017: AAO, Sydney

Tuesday 19 Sep 2017: RSAA Mt Stromlo, Canberra

Wednesday 20 Sep 2017: Swinburne University, Melbourne

Thursday 21 Sep 2017: University of Western Australia, Perth

Friday 22 Sep 2017: University of Queensland, Brisbane

Further details on venues will be provided closer to the date. Attendance is free and pre-registration will not be required. For those unable to attend any of these events in person, the AAO-based session will include an option for video-conference participation, and a recording will be made available.

The ITSO web site has been expanded to include some supplementary information about ESO, and links to the relevant sections of the ESO web site. Potential applicants are encouraged to register for an ESO User Portal account, which will also place you on the mailing list to receive ESO Science Announcements and Newsletters.
Tuesday Sep 19, 10:30
Caitlin Adams ()
Student Review: Caitlin Adams 30-month PhD review
Thursday Sep 14, 10:30
Javier Mujeto (Universidad Nacional Autonoma de Honduras)
Colloquium: Astronomy in the Classic Maya Period
The Mayan Classic period (250-900 CE) is recognised as the height of the arts, architecture and urbanism for the Maya, particularly in terms of astronomical knowledge. Observations of the celestial landscape arise in sculptures, buildings, calendars, numbering, writings and all Mayan cultural expressions. This talk will explore the site known as Copan Ruinas - a crucible of outstanding architecture and symbolic language that shows the role of time and cosmos in the religion, rituals, and social ends of the Maya people.

Dr. Javier Mejuto is a professor of Cultural Astronomy at the National Autonomous University in Honduras (Central America), conducting ethnographic work with Indigenous communities of Central America and archaeoastronomical fieldwork in southern Europe and Mesoamerica.
Thursday Sep 7, 10:30
Philip Hopkins (Caltech, USA)
Colloquium: Stars Re-Shaping Galaxies
The most fundamental unsolved problems in galaxy formation revolve around "feedback" from massive stars and black holes. I'll present new results from the FIRE simulations which combine new numerical methods and physics in an attempt to realistically model the diverse physics of the interstellar medium, star formation, and feedback from stellar radiation pressure, supernovae, stellar winds, and photo-ionization. These mechanisms lead to 'self-regulated' galaxy and star formation, in which global correlations such as the Schmidt-Kennicutt law and the global inefficiency of star formation -- the stellar mass function -- emerge naturally. Within galaxies, feedback regulates the structure of the interstellar medium, but more radically drives outflows which can actually change the dynamics, morphologies, and sizes of galaxies, in addition to transforming cusps into cores and suppressing star formation. We are actually reaching the point where different stellar feedback and stellar types can produce observable differences on extra-galactic scales. Finally, I'll discuss where stellar feedback fails, and additional feedback, perhaps from AGN, is really needed to explain observations.
Thursday Aug 31, 10:30
Stephanie Bernard (University of Melbourne/Swinburne)
Colloquium: Chasing the bright end of the z > 8 galaxy luminosity function with the BoRG
Using the Wide Field Camera 3 on the Hubble Space Telescope, the frontier of galaxy studies at z ~ 9-11, only 500 million years after the Big Bang, is currently being explored. While the WFC3 is a powerful instrument that has opened up a rich new area of discovery, including the most high-redshift galaxy currently known, its view is still limited. By adding in imaging and spectroscopic data from other space-based and ground-based sources, such as Spitzer's near-infrared IRAC camera, or the infrared MOSFIRE instrument on Keck, we can get a better view of the properties of these galaxies in the early Universe. I will present galaxy candidates and luminosity functions at z > 8 from our pure-parallel HST survey, the Brightest of Reionising Galaxies (BoRG) survey, and our Spitzer programme to followup over thirty of these candidates. I will also present results from our MOSFIRE programme to spectroscopically confirm reionisation-era candidates.
Tuesday Aug 29, 10:30
Student Review: 18 Month Review - Jacob Seiler
Thursday Aug 24, 10:30
John O'Meara (Saint Michael's College, USA)
Colloquium: Dare Mighty Things: The LUVOIR mission concept
In preparation for the 2020 Decadal Survey, NASA has formed four Science and Technology Definition Teams (STDTs) to create large mission concept studies for the next generation of large class missions. One of these mission concepts is LUVOIR: The Large Ultraviolet Optical InfraRed surveyor. LUVOIR is exploring two architectures, with primary apertures at 15.1 and 9.2 meters in size. LUVOIR will cover a similar range of wavelengths to HST, but with factors of tens to thousands increase in throughput. In this talk, I will describe the telescope concept, the instruments, and candidate science programs. I will leave ample time for discussion on other science programs, including a demonstration of our exposure time calculators with the goal of soliciting science program ideas from scientists at Swinburne.
Wednesday Aug 23, 10:30
Vy Tran (UNSW)
Colloquium: From the FOURGE to the FIRE: Tracking Galaxy Evolution Over 12 Billion Years
ZFOURGE and ZFIRE are sensitive extragalactic surveys that track how galaxies assemble over the past 12 billion years. ZFOURGE identifies and measures cosmological distances to approximately 70,000 objects using a custom set of near-infrared imaging filters. ZFIRE selects galaxies from ZFOURGE for spectroscopic follow-up to measure how baryons cycle between stars, winds, and the Inter-Stellar Medium (ISM). Here I highlight results that include mapping how galaxies are distributed in the distant universe, characterising the galaxies' spectral properties over cosmic time, and determining how galaxies differ depending on their neighbours.
Wednesday Aug 16, 10:30
Idit Zehavi (Case Western Reserve University)
Colloquium: Exploring the relation between galaxies and dark matter halos
The Halo Occupation Distribution (HOD) framework is a powerful approach for interpreting galaxy clustering measurements and constraining the galaxy-halo connection, as highlighted by analyses of the SDSS. We present new results for the redshift evolution of the galaxy content of halos as predicted by semi-analytic galaxy formation models. We further examine how the halo occupation functions vary with large-scale environment and halo formation time. This provides physical insight into the nature of galaxy assembly bias, and sets the foundation for extending the HOD approach and for creating realistic mock catalogs for upcoming surveys.
Thursday Aug 10, 10:30
Stuart Sim (Queen's University Belfast, UK)
Colloquium: Modelling thermonuclear supernovae: how to blow up a white dwarf star
Aside from being spectacular displays in their own right, Type Ia supernova explosions have a key role in measuring the expansion history of the Universe and synthesizing the iron group elements. But what is their origin? That Type Ia supernovae arise from exploding white dwarfs is relatively well-established but the manner in which the explosion is ignited and how this can be determined from what we observe remain hotly debated issues.
I will discuss the theoretical modelling of Type Ia supernovae with particular focus on how radiative transfer simulations can be used to test explosion scenarios. I will argue that understanding the diversity of thermonuclear supernovae requires us to investigate a variety of different progenitor scenarios. Specifically, I will present recent results from our work on both Chandrasekhar mass white dwarf explosion scenarios and sub-Chandrasekhar mass models.
Tuesday Aug 1, 10:30
Garth Illingworth (University of California Santa Cruz, USA)
Colloquium: Galaxies at Cosmic Dawn: Exploring the First Billion Years with Hubble and Spitzer --- Implications for JWST
Hubble has revolutionized the discovery and study of very distant galaxies through its deep imaging surveys. Together the HST WFC3/IR and ACS cameras have opened up the exploration of the universe in the first billion years after the Big Bang. I will discuss what we have learned about the earliest galaxies during the reionization epoch at z>6 from the remarkable HST and Spitzer imaging surveys (e.g., HUDF/XDF, GOODS, HUDF09/12 and CANDELS), as well as surveys of galaxy clusters like the Frontier Fields (HFF). Lensing clusters provide extraordinary opportunities for characterizing the faintest earliest galaxies, but also present extraordinary challenges. Together these surveys have reliably established the volume density of galaxies in the first billion years down to extremely faint levels around -14.5 mag. The results from deep UV luminosity functions from Hubble, combined with the recent results from Planck, indicate that galaxies dominate the UV ionizing flux that reionized the universe. Some of the greatest surprises have come from the discovery of very luminous galaxies at z~8-11, around 400-650 million years after the Big Bang. Spectroscopic followup of these very rare, bright galaxies has confirmed redshifts from z~7 to z~11, and revealed, surprisingly, strong Lyalpha emission near the peak of reionization when the HI fraction in the IGM is high. The small sizes of galaxies at high redshifts, from analysis of the HFF cluster samples, reveal objects that, remarkably, are as small as globular clusters and dwarf galaxies. The recent confirmation of a z=11.1 galaxy, just 400 million years after the Big Bang, by a combination of Hubble and Spitzer data, pushed Hubble into JWST territory, far beyond what we ever expected Hubble could do. Twenty years of astonishing progress with Hubble and Spitzer leave me looking to JWST to provide even more remarkable exploration of the realm of the first galaxies at "Cosmic Sunrise". The latest results on the sizes of distant galaxies, on the star formation rate density at z~10 and from Planck indicating that reionization began around z~10 together have significant implications for the detectability of the "first galaxies" with JWST.
Thursday Jul 20, 10:30
Brice Menard (Johns Hopkins, USA)
Colloquium: De-projecting astronomical surveys
Observations of celestial objects are inherently a 2D mapping on the sphere but astrophysical studies usually require the knowledge of 3D positions. For most extragalactic sources, this estimation relies on photometric redshifts which require strong assumptions and can lead to catastrophic failures. In this talk I will show how it is possible to use clustering measurements to infer redshifts for any type of extragalactic sources. I will show how to turn this idea into a new tool for redshift estimation and show how accurate it is. I will then present applications of this "clustering-redshift" technique using various datasets at UV, optical, IR and radio wavelengths, and will show a number of surprises.
Thursday Jun 22, 10:30
Adam Deller (Swinburne)
Colloquium: Radio pulsars: the physics lab with a catch
Neutron stars are an incredibly versatile laboratory for studying physics, creating conditions that we cannot replicate on Earth. Over the last 5 decades, these laboratories have provided numerous breakthroughs, particular in the study of gravitation, where radio pulsar timing provided the first indirect evidence of gravitational waves and is poised to detect the low-frequency gravitational wave background created by binary supermassive black holes. What is remarkable is that so much of this progress has been made despite huge gaps in our knowledge about the laboratories themselves! In this talk I will discuss some of these gaps, the ongoing efforts to fill them in, and what the implications the success or failure of these efforts will have on future radio pulsar science with (for instance) the Square Kilometre Array.
Tuesday Jun 20, 10:30
Chris Curtin ()
Student Review: Curis Curtin 30-month Review
Wednesday Jun 14, 10:30
Student Review: Vivek 30mth PhD review
Tuesday Jun 6, 10:00
Matt Agnew (Swinburne)
Student Review: Matt Agnew's 18 month review
Thursday Jun 1, 10:30
Ray Volkas (University of Melbourne)
Colloquium: Department of Physics and Astronomy Colloquium
Department of Physics and Astronomy Colloquium
Friday May 26, 10:30
Camila Correa (Leiden University, Netherlands)
Colloquium: Morphology and color of the EAGLE galaxy population
I investigate the dependence of kinematic-based galaxy morphology on intrinsic colour and stellar mass in the EAGLE cosmological hydrodynamical simulations. I use intrinsic u-r colours and measure the fraction of kinetic energy invested in ordered corotation of 3562 galaxies at z=0 with stellar masses larger than 10^10 solar masses. I find that EAGLE produces a galaxy population whose morphology correlates with the colour bimodality for central and satellite galaxies alike. The red-sequence is mostly populated by elliptical-type galaxies and most of blue-cloud galaxies are disc-type. In this talk I will discuss these findings and through visual inspection of gri-composite images, I will show that kinematic morphology correlates strongly with visual morphology. Furthermore I will show the coevolution of color and morphology of EAGLE galaxies along with their merger history. Finally, I will discuss the impact of mergers on morphological transformations.
Thursday May 25, 10:30
Richard Plotkin (Curtin University)
Colloquium: Black Holes at the Lowest Luminosities
Both stellar mass black holes in transient X-ray binary systems (BHXBs) and supermassive black holes (SMBHs) spend most of their lives accreting very weakly compared to their Eddington luminosities (L_Edd), in the so-called quiescent regime (<1e-5 L_Edd). However, despite quiescence being the most common accretion state, there are still several open questions regarding the nature of accretion at such low luminosities. I will discuss how black hole accretion flows and their jets evolve while BHXBs transition into quiescence, largely by focusing on recent multiwavelength observations of the long orbital period BHXB V404 Cygni (which underwent a spectacular outburst in 2015, after spending 26 years in quiescence). I will also describe further changes exhibited by shorter-period black hole X-ray binaries, as they fade to the lowest detectable luminosities (~1e-9->1e-8 L_Edd), and how jet properties (e.g., particle acceleration, total power, etc.) may depend on accretion rate. The new constraints presented here anchor the low-luminosity end of the black hole accretion spectrum, thereby improving the utility of using radiative signatures to learn about highly sub-Eddington BHXBs and SMBHs (including, e.g., Sgr A* at the Galactic Centre), and also increasing the efficacy of using multiwavelength surveys to uncover new populations of weakly accreting black holes.
Thursday May 18, 10:30
Enrico di Teodoro (ANU)
Colloquium: A snapshot of my research activity: galaxy kinematics and outflows
I will present some results in my main fields of study: the kinematics of disk galaxies and the Milky-Way nuclear wind. In the first part of the talk, I will address the problem of deriving reliable kinematics from low-resolution observations of star-forming galaxies: I will describe a new software (3D-Barolo) to fit three-dimensional tilted-ring models to emission-line data and I will show some significant applications of the algorithm both in the local and in the high redshift Universe. In the second part of the talk, I will review the current understanding of the Milky-Way galactic wind and I will illustrate how atomic hydrogen (HI) can be successfully used to infer the physical properties of the outflow.
Tuesday May 16, 11:30
Student Review: Robert Dzudzar confirmation review
Thursday May 11, 10:30
Bonnie Zhang (ANU)
Colloquium: Precision cosmology with Type Ia supernovae: the Hubble constant and dark energy
Type Ia supernovae (SNe Ia) played a vital role in the discovery of dark energy, almost two decades ago. Today, SNe Ia remain excellent distance indicators, and are instrumental to answering two of the most important questions in contemporary cosmology, at opposite ends of the distance scale: what is the value of the Hubble constant H0, and what is the nature of dark energy? Underlining both of these is the question of whether the standard LambdaCDM model can adequately describe our Universe, or if new physics is required to explain observations. In this talk I will discuss the current 'tension' between local SN Ia based measurements of H0, and values derived from Planck observations of CMB anisotropies assuming LambdaCDM. In particular, I will present my recent work to measure H0 using low-redshift SNe Ia, calibrated by Cepheid variables. This is a blind end-to-end reanalysis of Riess et al. 2011, revisited with an updated SN Ia analysis framework (including a covariance matrix based approach to error analysis) and a simultaneous fit to all data sets -- differences which increase the relative error in H0 compared to previous analyses of the same data set. With reference to this work, I will argue for the importance of blind analyses. Finally, I will summarise efforts of the Dark Energy Survey to use SNe Ia as one of four cosmological probes to measure dark energy, including major Australian contributions through OzDES, and outline future directions for contemporary supernova cosmology.
Thursday May 4, 10:30
Yuval Birnboim (The Hebrew University of Jerusalem)
Colloquium: Cold flows in haloes and filaments; when they occur, and how they interact with haloes and galaxies.
Virial shocks are expected to form around haloes, as well as around cosmic filaments and sheets. However, due to cooling, gas that accretes onto haloes and filaments does not always heat to the virial temperature, leading to unstable, free falling gas (a.k.a "cold flows"). I will summarize old theoretical results about accretion onto haloes, and present some recent work of gas accretion onto filaments.
Once cold flows penetrate through hot virialized haloes, supersonic Kelvin Helmholtz instability occurs, with specific patterns of unstable KH modes. Finally, as cold flows smash into the galaxy, magnetic fields can play a non-trivial role in the way this gas actually mixes with the ISM.
Tuesday May 2, 10:30
Shivani Bhandari (Swinburne)
Student Review: Shivani Bhandari's 30 month review
Monday Apr 24, 15:00
Mark Wilkinson (University of Leicester)
Colloquium: Dwarf spheroidal galaxies: cosmological probes on our doorstep
The Local Group dwarf spheroidal galaxies (dSphs) are widely recognised as valuable targets for the study of the processes of galaxy formation on small scales. However, there are a number of major outstanding questions (commonly referred to as the "Missing Satellites" and "Too Big To Fail" problems) whose resolution requires us to delve into the evolution of both the dark matter and baryonic components of dSphs. In this talk, I will discuss a new mass modelling technique which uses N-body simulations to estimate the masses of dSphs to much larger radii than has previously been possible. Using this approach, we have been able to constrain the mass of the Carina dSph both at the current epoch and at the time it fell into the Milky Way, finding a surprisingly low pre-infall mass. I will also present results from a study which uses the internal kinematics of dSphs to make predictions for the dark matter annihilation signals we might expect to see from their inner regions. Finally, I will discuss on-going work to study the baryonic processes which impact on the evolution of dSphs and which suggests that stochasticity in the star formation process in low-mass galaxies is responsible for the non-linearity of the mapping between simulated dark matter haloes and observed satellite galaxies.
Thursday Apr 20, 10:30
David Rupke (Rhodes College)
Colloquium: Do Supermassive Black Holes Help to Regulate Galaxy Evolution and Black Hole Growth?
Supermassive black holes that are rapidly accreting matter (and sometimes outshining their host galaxies) were the first sources discovered at cosmological redshifts. Despite progress in the intervening half-century, key questions remain about how black holes affect the evolution of their host galaxies, as well as how they self-regulate their own growth. I will discuss so-called "AGN feedback," which is a topic of intense theoretical and observational interest. I will focus in particular on what we are learning from multiwavelength observational studies of the nearest and brightest active galactic nuclei.
Wednesday Apr 5, 11:30
Rachel Webster (University of Melbourne)
Colloquium: Looking at Quasars from a Different Direction
There has been a long-held belief that there should be a simple unifying physical model for quasars, similar to the primary characterisation of stars by their mass. However its form and shape has proven elusive. This quest has been partly frustrated by the fact that quasar geometry and emission is axi-symmetric. I will describe new results from our microlensing studies of macro-imaged quasars, that aim to develop a coherent picture of the inner regions of quasars, including the accretion disk and the broad emission line region.
Tuesday Mar 28, 10:30
Renee Spiewak (Swinburne)
Student Review: Confirmation of Candidature
Friday Mar 24, 11:30
Tyler Bourke (SKA)
Colloquium: The Square Kilometre Array - Science and Status Update
The Square Kilometre Array (SKA) will be the world's largest radio telescope when Phase 1 is completed in the next decade. The past few years have seen great progress toward this goal, with construction to start in 2019 and science operations anticipated to begin in 2024. In this presentation I will provide a status update on SKA activities, with a focus on the science it will enable.
Thursday Mar 16, 10:30
Caroline Foster (AAO)
Colloquium: The true shape of galaxies
The intrinsic or true three-dimensional shape of galaxies is one of their most fundamental characteristic. Yet, due to projection effects, the true shape of galaxies is a difficult property to measure accurately. The most reliable method for inferring intrinsic shapes require large samples of spatially resolved stellar kinematic maps. Large IFU surveys are now enabling this type of science to be done accurately on carefully selected samples of galaxies. I am using the SAMI Galaxy Survey to uncover the intrinsic shape of various carefully selected galaxy samples. Preliminary results will be presented.
Thursday Mar 2, 10:30
Steven Janowiecki (University of Western Australia)
Colloquium: Gas and star formation in galaxies: the role of environment and (almost) dark galaxies
I will talk about recent work studying gas and star-formation in samples of galaxies. In particular, using the new xGASS survey, we have found unusually gas-rich and star-forming central galaxies in small groups, which we interpret as evidence of feeding from the cosmic web. At the other extreme, the ALFALFA HI survey is finding gas-rich galaxies with almost invisible stellar populations. These (almost) dark galaxies are exceptionally inefficient at forming stars and may be related to the recently re-discovered class of "ultra-diffuse" galaxies.
Thursday Feb 23, 10:30
Tara Murphy (University of Sydney)
Colloquium: Making the leap: from academic to start-up founder
My research is in radio astronomy, in particular in the dynamic radio sky, using intelligent algorithms to find rare objects in large datasets. In 2013, along with a colleague and two PhD students I took a leap into the unknown and started a company "Grok Learning" that provides online computing education for school students, teachers and universities. We now have thousands of users from around the world, and a team of 10 staff including the founders.
In this talk I'll discuss how our academic training (as astronomers and computer scientists) was helpful in the business world, but also the challenges you might face. How does running your own business compare to a job in academia? What astronomy skills are useful in the business world? What should you do if you're interested in starting a business?
I'm happy to leave plenty of time for discussion, so bring your questions!
Tuesday Feb 7, 10:30
Uros Mestric ()
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