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Colloquia Series

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

Swinburne Virtual Reality Theatre
AR Building, Room 104
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2016 Colloquia

Thursday Sep 15, 11:30
Michael Brown (Monash)
Colloquium: TBA
Abstract: TBA
Thursday Aug 25, 11:30
Jill Rathborne (CSIRO Astronomy and Space Science)
Colloquium: TBA
Abstract: TBA
Tuesday Aug 2, 11:30
Bogdan Ciambur (CAS)
Student 18 month Review:
Abstract: TBA
Thursday Jun 30, 11:30
Tiantian Yuan (ANU)
Colloquium: TBA
Abstract: TBA
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 ()
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)
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)
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 ()
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)
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 ()
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 ()
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)
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)
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.