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Colloquia Series

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

Swinburne Virtual Reality Theatre
AR Building, Room 104
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2017 Colloquia

Tuesday Dec 12, 10:30
Vardha Bennert (California Polytechnic State University, USA)
Colloquium: TBA
Abstract: TBA
Thursday Nov 16, 10:30
Bob Nichol (University of Portsmouth, UK)
Colloquium: TBA
Abstract: TBA
Tuesday Oct 24, 10:30
Leonie Chevalier ()
Student Review: Leonie Chevalier 18-Month Review
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: TBA
Abstract: TBA
Thursday Sep 21, 10:30
Tanya Hill (Melbourne Planetarium, Scienceworks)
Colloquium: Melbourne Planetarium - tapping into the public appeal of astronomy
Astronomers well recognise the appeal of their subject among the wider public. Astronomy has beautiful, eye-catching imagery, its discoveries are attention grabbing and evoke the world of science fiction, and at its most basic level, everyone has the potential to explore and be captivated by the night sky. Our understanding of the universe has changed greatly since the world's first demonstration of a planetarium projector in Munich, Germany, 1923. Here's my review of how Melbourne has continued to tap into the public's curiosity for astronomy and evolved with the times to keep the public informed about the universe we live in.
Thursday Aug 31, 10:30
Stephanie Bernard (University of Melbourne/Swinburne)
Colloquium: TBA
Abstract: TBA
Tuesday Aug 29, 10:30
Student Review: 18 Month Review - Jacob Seiler
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 Lyα 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 ()
Student Review: Uros Mestric confirmation review