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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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2015 Colloquia


Thursday Dec 17, 11:30
Jessica Dempsey (East Asian Observatory)
Colloquium: JCMT: submillimeter opportunities for Australia with the East Asian Observatory
Following the East Asian Observatory assuming operations of the James Clerk Maxwell Observatory in March 2015, the Observatory has had an extremely successful and productive year. The JCMT is the premier submillimeter facility in the northern hemisphere for wide-field continuum and heterodyne observations, and maintains a suite of instrumentation that offers high-impact science opportunities well into the next decade. The EAO intends to accelerate these achievements by embarking on an ambitious program of instrument upgrades and additions that will further extend the JCMT's capabilities. An overview of the East Asian Observatory and its vision will be described, and the JCMT operations and capabilities will be presented. The merits of the new organisation will be presented with reference to how and why Australian astronomy would benefit from joining this new partnership and this
premier observing facility.
Tuesday Dec 15, 11:30
Sarah Hegarty ()
Student Review: Sarah Hegarty's Confirmation of Candidature Review
Thursday Dec 10, 11:30
Jennifer Piscionere (Swinburne CAS)
Colloquium: The Changing Spatial Distribution of Satellite Galaxies in Dark Matter Halos
Understanding the changing relationship between galaxies and their host dark matter halos is key to understanding the growth of structure in the Universe as well as the physics that dictates how galaxies assemble and evolve. We can explore these processes by studying galaxy clustering on scales less than 1 Mpc; clustering on these scales is directly related to the radial distribution of satellite galaxies. My work focuses on measuring the very small scale clustering of Sloan Digital Sky Survey galaxies. I model this clustering using a fully numerical halo model that populates dark matter halos in N-body simulations to create realistic mock galaxy catalogs. I will talk about the successes and difficulties of studying the clustering of galaxies in different luminosity classes and show how the satellite distribution profile is luminosity dependent. My new results also show, for the first time, a significant evolution in the very small scales clustering of massive galaxies over cosmic time. The clustering of the lower redshift sample is substantially steeper, indicative of satellite galaxy population that has grown dramatically over the course of cosmic time.
Wednesday Dec 9, 11:30
()
Student Review: Alex Codoreanu's mid-candidature review
Tuesday Dec 8, 14:00
Dany Vohl ()
Student Review: Dany Vohl's Mid-Candidature Review
Friday Dec 4, 11:30
Lisa Harvey-Smith (CSIRO)
Colloquium: The Australian SKA Pathfinder: Early Science results
The Australian SKA Pathfinder (ASKAP) is a radio telescope comprising thirty-six dishes in Western Australia. It features an award-winning 'radio camera' designed to facilitate wide-are surveys of the radio sky between 700-1800 MHz. The main science goals of ASKAP are to explore the properties and evolution of radio galaxies, the neutral gas content of galaxies, cosmic magnetic fields and explore the radio transient sky.
For the past 12 months, CSIRO has been carrying out a commissioning and early science program with the 6-antenna test array of ASKAP, primarily to test the technology and learn how to optimally calibrate data in preparation for the major ASKAP surveys. In this talk, the ASKAP Project Scientist will show some of the first science results from ASKAP and report on progress towards early science surveys, due to begin in mid-2016.
Thursday Nov 26, 11:30
Sarah Martell (UWS)
Colloquium: New evidence on the role of globular clusters in the assembly of the Galactic halo
Hierarchical accretion models for galaxy formation predict that the majority of stars in the halo of a spiral galaxy should have formed within dwarf galaxies that were later accreted by the larger galaxy. In 2010, we used a rough chemical tagging approach to identify stars in the Milky Way halo that had likely formed in globular clusters, using the light-element abundance anomalies that are well-studied in Galactic globular clusters. This was the first identification of this population of halo stars that formed in situ, and subsequent studies have confirmed our initial result. Ideally one would use this chemically taggable population, which comprises around 2.5% of the halo, to explore the importance of in situ star formation in halo assembly. However, the interpretation is strongly dependent on models for globular cluster formation, mass loss, and dissolution. I will present a new search for globular cluster migrants in the Galactic halo in SDSS-III APOGEE survey data, and discuss the interpretation of this population in the light of recent theoretical work on globular cluster formation that is upending many previous assumptions.
Tuesday Nov 24, 12:30
Themiya Nanayakkara ()
Student Review: Themiya: Pre-submission Review
Thursday Nov 19, 11:30
Hilton Lewis (Keck Observatory)
Colloquium: The W. M. Keck Observatory: Current Status and Future Plans
The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes near the summit of Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectroscopy and world-leading laser guide star adaptive optics system. The Director of Keck Observatory, Mr. Hilton Lewis, will present the current status of the observatory along with plans for future upgrades and new instrumentation.
Thursday Nov 12, 11:30
Sarah Kendrew (University of Oxford)
Colloquium: Integral field spectroscopy of high-redshiftgalaxies in the ELT era
High-resolution cosmological simulations are increasingly valuable for preparing surveys and studying the capabilities of future instrumentation. In combination with dedicated instrument simulators and astrophysical modelling methods, data from cosmological simulations can be transformed into realistic observations of a range of astrophysical targets. I'll present the tools developed to produce observations of a RAMSES simulated star-forming galaxy at z=3 with the E-ELT first light integral field spectrograph HARMONI. Using the data, we investigate how well the properties of the star particle data, in particular the stellar kinematics, can be recovered from the simulated observations. In addition, by adjusting parameters in the instrumental simulation software, we use the simulation data to demonstrate how PSF convolution affects the ability to recover the galaxy’s properties, even for high-resolution adaptive optics-assisted observations. Finally, I'll discuss future opportunities for extending the work to include more detailed physics, or to larger samples of galaxies.
Thursday Nov 5, 11:30
Claudio Gheller (Swiss National Supercomputing Centre)
Colloquium: Astrophysics on the GPU
Abstract: TBA
Friday Oct 30, 11:30
Joshua Peek (Columbia University)
Colloquium: The Diffuse Universe: Catalogs, Continuum, Combination
Astronomy has always been a science of catalogs: catalogs of stars, galaxies, quasars, and planets. While most of the light in the Universe comes from these dense objects in the darkness, the contents of the universe are largely diffuse. Dark energy, dark matter, plasma, and gas make up 99.8% of the mass-energy budget of the Universe and cannot be easily cataloged. If we want to understand how the objects in the universe came to be, we must appeal to the largely invisible diffuse phase that formed them. I will try to make sense of this conundrum in three ways. The first is to use the cataloged objects to discern things about the intervening gas: through dust reddening we can measure the location and density of metal enriched gas in the Galaxy and beyond. The second is to examine the velocity-resolved emission from the gas. To do this we invent statistically robust ways to measure the shape structure of the gas, where much of the information about the diffuse phases hides. The third is to combine the two, catalogs and continuum, to delve into the 4D structure of our Galaxy. I will discuss a method in development, Kinetic Tomography, which will hopefully help us understand how the Galaxy came to be the way it is today.
Friday Oct 23, 15:30
Jeremy Mould (CAS)
Colloquium: The SABRE experiment at the Stawell Underground Physics Lab
Thursday Oct 22, 11:30
Stephanie Juneau (CEA Saclay)
Colloquium: Star Formation and Black Hole Growth in Strongly Evolving Galaxies
Globally, we know that galaxies have strongly evolved across cosmic time, going through a peak of activity and stellar growth when the universe was 1/4 to 1/2 of its current age, and steadily declining since. What is lesser known, but currently under a strong debate, are (1) the physical gas conditions inside galaxies over this period of strong evolution, and (2) the underlying connection between supermassive black holes -- with masses between a few millions to billions solar masses -- and their surrounding host galaxies. After giving an overview of the current status of galaxy-black hole co-evolution, I will show how even our ability to detect active black holes depends on galaxies' physical state and evolutionary phase. I will then present improved methods and new clues that will allow us to achieve a clearer picture of these two crucial aspects of galaxy evolution.
Tuesday Oct 20, 14:00
George Bekiaris ()
Student Review: George Bekiaris, 30-month review
Tuesday Oct 20, 11:30
Igor Andreoni (CAS)
Student Review: Igor Andreoni 6-month Review
Igor will give his 6-month PhD review talk
Thursday Oct 15, 11:30
Emily Petroff (Swinburne CAS)
Colloquium: Detection and follow-up of fast radio bursts
Abstract:
Fast radio bursts (FRBs) are quickly becoming a subject of intense interest in time-domain astronomy. FRBs have the exciting potential to be used as cosmological probes of both matter and fundamental parameters, but such studies require large populations. Advances in FRB detection using current and next-generation radio telescopes will enable the growth of the population in the next few years. Real-time discovery of FRBs is now possible with 4 sources detected in real-time within the past 1.5 years at the Parkes telescope. I will discuss the developing strategies for maximising real-time science with FRBs including polarisation capture and multi-wavelength follow-up. Particularly, I will focus on the real-time detections of three new sources that provide a test bed for fast radio burst science. I will also discuss how our response to these events can inform next generation surveys and pave the way for the enormous number of FRB discoveries expected in the SKA era.
Wednesday Oct 14, 11:30
Elodie Thilliez ()
Student Review: Elodie Thilliez 30 month PhD review
Tuesday Oct 13, 14:30
()
Student Review: Antonio Bibiano, 30 month review
Thursday Oct 8, 11:30
Angel Lopez-Sanchez (AAO and Macquarie University)
Colloquium: Dwarf star-forming galaxies and the assembly of spiral galaxies
In this Colloquium I will review my multi-wavelength analysis of star-forming dwarf galaxies combining deep optical/NIR, UV, and 21-cm HI data and how this study has led me to get conclusions about the mass assembly in nearby spiral galaxies. First I will show some particular results in blue compact dwarf galaxies (BCDGs), such as NGC 5253 or Tol 30, that reinforce the hypothesis that interactions with or between low-luminosity dwarf galaxies or HI clouds are the main trigger mechanism of the star-forming bursts. I will also show some examples of starbursts induced by dwarf galaxies or HI clouds in galaxy groups (HCG 31 and Mkn 1097). Interaction features also are found in apparently isolated BCDGs when observed in HI. Finally, I will present the results of the analysis of the ionized and neutral gas in the interacting galaxy pair NGC 1512/1510. NGC 1510 is a BCDG and NGC 1512 is a spiral galaxy which hosts hundreds of UV-bright stellar clusters in its outskirts (a XUV disc). The analysis of many of these knots was possible thanks to the 2dF/AAOmega instrument at the 3.9m AAT. We confirm the detection of ionized gas in the majority of these UV-rich regions and characterize their physical properties, chemical abundances, and kinematics. When combined with the available UV and HI results our new optical data are providing key clues about local star-formation processes in galaxies, the interplay between the ISM and the IGM, the metal redistribution in the outer gaseous discs of spiral galaxies, and the role of interactions with dwarf galaxies in the evolution of the spiral galaxies.
Thursday Oct 1, 11:30
Anne Hutter (Swinburne CAS)
Colloquium: Probing reionization with Lyman Alpha emitters and the 21cm signal
The Epoch of Reionization marks a cataclysmic event in the history of the Universe. Since reionization affects all subsequent structure formation through a number of feedback effects, it is crucial to pin down the topology of reionization. However, the exact progress of reionization and the nature of galaxies driving reionization remain open questions due to a poor understanding of the escape fraction of ionizing photons from the galaxies.
In order to understand the importance of the ionization state of the IGM, the escape fraction of ionizing photons and dust in the ISM on the visibility of Lyman Alpha emitters (LAEs), we have built a model for high-redshift LAEs by coupling cosmological simulations with a dust model and radiative transfer. Comparison of our model results with the observed LAE Lya and UV luminosity functions at z=6.6 reveals a 3D degeneracy between the ionization state of the IGM, the ionizing photon escape fraction and the ISM dust distribution. The LAE clustering amplitude is only sensitive to reionization and allows us to constrain reionization further, but impedes further constraints on galactic properties. Since the 21cm brightness temperature is sensitive to the ionization fraction and thus to the ionizing photon escape fraction, we investigate whether cross-correlating the 21cm signal with LAEs enables us to break the degeneracy between galactic properties.
Tuesday Sep 29, 15:30
Mark Hutchison ()
Student Review: Mark Hutchison 30 month review
Tuesday Sep 22, 11:30
Angela Garcia ()
Student Review: Angela Garcia 18 month review
Thursday Sep 17, 11:30
Paul Lasky (Monash)
Colloquium: Choose your own adventure: gravitational wave astrophysics
Abstract:
Gravitational wave science is entering a truly exciting era. Initial LIGO surpassed design sensitivity, and the so-called ‘Advanced Detector Era’ is beginning in earnest this month. The Parkes Pulsar Timing Array also reached design sensitivity in 2015, with the lack of a positive gravitational wave signal altering our understanding of binary supermassive black hole evolution. I will review recent advances in our understanding of gravitational wave emission mechanisms relevant for both LIGO and PTAs. At each step I will assess detectability of the signal in the near future, and discuss what can be learnt from future detections and non-detections.
Tuesday Sep 15, 11:30
Sabine Bellstedt (CAS)
Student Review: 6 month review - Sabine Bellstedt
Thursday Sep 10, 11:30
Paola Oliva (CAS)
Colloquium: Brightest Cluster Galaxies as seen by integral-field spectrographs
Abstract:
The current definition of Brightest Cluster Galaxies (BCGs) refers to the central dominant galaxy in a cluster. These galaxies are known for being extremely massive and are predicted to have gone through more mergers than common less massive early-type galaxies. The history of BCG evolution can be traced by their current stellar kinematics and stellar populations.
Integral-field spectroscopy (IFS) allows us to study in detail the spatially-resolved BCGs stellar kinematics and populations and the relationship with their intrinsic accretion histories.
This talk will summarise the observations of BCGs using IFS. To date these observations are suffering of low number statistics. However, the results are opening new questions, which will be later studied by ​larger ​
IFS surveys such as SAMI and MaNGA.
Tuesday Sep 8, 11:30
Caitlin Adams ()
Student Review: Caitlin Adams 6-month review
Monday Sep 7, 15:00
()
Student Review: Adam Stevens, 30 month review
Tuesday Sep 1, 11:30
Luis Torres ()
Student Review: Luis Torres 30-month review
Thursday Aug 27, 11:30
Katie Mack (Melbourne University)
Colloquium: Dark Matter in the Cosmic Context
Abstract:
Dark matter forms the foundation for all cosmic structure, and its annihilation, decay, or other particle interactions have the potential to affect early structure formation by injecting energy into local gas. I will discuss the status of the quest to identify dark matter, major unsolved problems, and how dark matter particle interactions can affect the earliest cosmic structures. I will also give an update on plans to carry out a dark matter direct detection experiment in rural Victoria. [Papers: arXiv: 1309.7783, 1411.3783]
Tuesday Aug 25, 11:30
Katharina Lutz ()
Student Review: Katharina Lutz 18 month review
Thursday Aug 20, 11:30
Eric Thrane (Monash)
Colloquium: Searching for gravitational waves with Advanced LIGO
Abstract:
The LIGO experiment seeks to detect gravitational waves--minute ripples in the fabric of spacetime caused by some of the most energetic events in the Universe. Commissioning of the newly upgraded Advanced LIGO is well underway, and we expect our first science quality data later this year. Advanced LIGO will see gravitational-wave sources ten times further than the previous Initial LIGO experiment, facilitating the detection of potentially dozens of events every year. The coming era of gravitational-wave astronomy will yield important results for astrophysics, cosmology, and fundamental physics. In this talk, I will describe the status of Advanced LIGO commissioning and discuss some the astrophysical sources we hope to detect.
Thursday Aug 13, 11:30
David Rebolledo (University of Sydney)
Colloquium: Scaling relations of CO resolved structures in nearby spiral galaxies, and what we can learn from the Carina Nebula
Abstract:
We report high spatial resolution observations of Giant Molecular
Clouds (GMCs) in the nearby spiral galaxies NGC6946, M101 and NGC 628
obtained with the Combined Array for Research in Millimeter-wave
Astronomy (CARMA). We observed CO(1→0) over regions with active
star formation extending from 2 kpc to 15 kpc galactocentric radius.
Higher resolution observations of CO(2→1) toward the brightest
regions observed in CO(1→0) have allowed us to resolve some of
the largest GMCs. Using a Bayesian fitting approach, we generate
scaling relations for the properties of the structures identified in
this work. We do not find evidence for a power law relation between
size and line width in our sample of galaxies. We analyze the scaling
relation between the ΣSFR and ΣH2, known as the
Kennicutt-Schmidt (K-S) relation. We find super-linear K-S relations
for the identified structures for the three galaxies. The K-S relation
is sub-linear when we use an uniform grid to define the regions. For
NGC 6946 and M101 we find regions where the star formation efficiency
(SFE) shows marked peaks at specific galoctocentric radii. On the
other hand, the distribution of SFE in NGC 628 is more contiguous. As
a Galactic counterpart analysis, we have mapped the 12CO, 13CO & C18O
lines over the Carina Nebula using the Mopra telescope. With the CO
map in hand, we now are able to fully characterise the molecular
environments of the Carina Nebula, obtaining their masses and
kinematic properties. We will present preliminary results of the
analysis performed on Mopra CO images which combined with far-infrared
data from the Herschel space telescope allow us to determine the
fraction of the dust-derived gas mass that is in molecular form and
investigate the spatial variation of the XCO factor across this active
star forming region. The integrated properties of star forming
complexes in nearby galaxies will be able to be compared to the
picture we determine for Carina.
Thursday Aug 6, 11:30
Nicolas Caballero (Max Planck Institute for Radioastronomy)
Colloquium: Gravitational Wave detection with Pulsar Timing Arrays and noise characterisation
Abstract:
Millisecond pulsars (MSPs) have remarkable rotational stability that allows them to be used as accurate cosmic clocks. Systematic timing observations of an MSP ensemble in random sky positions, known as a Pulsar Timing Array (PTA) can lead to the direct detection of low-frequency Gravitational Waves (GW). The expected GW signal is expected to be weaker or comparable with low-frequency noise in the data, either from the pulsar's rotational instabilities, interstellar medium effects or systematic noise. Noise characterisation is therefore a central part of the GW detection process, for which various techniques are developed. In this talk I will give an overview of the how GWs are searched with pulsar timing data, and recent results in low-noise characterisation in the European Pulsar Timing Array data.
Thursday Jul 23, 11:30
Claudia Lagos (ESO)
Colloquium: The interstellar medium of galaxies in semi-analytic models and hydro-dynamic simulations
Abstract:
Observations of the gas content of galaxies, such as carbon monoxide, far-IR lines, and 21cm, are becoming common place, with thousands of galaxies at a wide range of cosmic epochs being studied. This has pushed galaxy formation simulations to start addressing how the different phases of the interstellar medium correlate with other galaxy properties and how they evolve in the cosmological context. There are several observational results that need to be addressed by simulations, such as (i) high-redshift galaxies have higher molecular gas fractions and star formation rates than local galaxies, (ii) scaling relations show that the atomic-to-stellar mass ratio decreases with stellar mass in the local Universe, with early-type galaxies exhibiting a remarkable wide range of gas fractions, (iii) the global abundance of atomic hydrogen evolves weakly. I will show how modern cosmological simulations of galaxy formation attempt to put together these pieces and highlight how we are treating this problem using the GALFORM semi-analytic models and the EAGLE hydro-dynamic simulations.
Thursday Jul 16, 11:30
Christopher Hales (NRAO)
Colloquium: Magnetic Fields in Large Scale Structure
The magnetic history of the Universe is uncharted. Measurements of magnetic fields on scales larger than galaxy clusters are needed to distinguish between fields generated in the primordial Universe and those generated at later epochs, with implications for particle physics, cosmology, and astrophysics. Yet such measurements remain elusive. In this talk I will review mechanisms for generating magnetic fields across cosmic time, implications for post-recombination physics, and current observational constraints on intergalactic magnetic fields. I will describe my efforts to develop a novel statistical probe of the magnetic
field power spectrum in cosmic web filaments using Faraday rotation measures. I will introduce CHILES Con Pol, a forthcoming ultra-deep 1.4 GHz radio survey with the Karl G. Jansky Very Large Array. CHILES Con Pol will reach an unprecedented SKA-era rms sensitivity of 400 nJy, entering new parameter space for studies of galaxy evolution and enabling the first robust constraints on the intergalactic magnetic field power spectrum.
Thursday Jul 2, 11:30
David Coward (UWA)
Colloquium: The Zadko Telescope: a fully robotic telescope for transient source and multi-messenger astronomy
The Zadko Telescope is a fully robotized 1-m optical facility, operating in the Gravity Precinct, about 80 km north of Perth. In this presentation, I will provide an overview of the history, recent significant upgrades to the infrastucture, and collaborative science. Presently, the system triggers automatically after receiving alerts from the Swift satellite (GRBs), and neutrino candidate alerts from the Antares neutrino telescope. An automated image processing system produces fully calibrated images downloadable from the internet. In addition, the system uses a dynamic prioritizing scheduling system, allowing several projects operating in the background - including a supernovae search, monitoring QSOs, photometry of slow rotating asteroids and others. I will also discuss, potentially new science opportunities that could be enabled by the facility in the near future.
Tuesday Jun 30, 11:30
Bogdan Ciambur (Swinburne CAS)
Student Review: Bogdan Ciambur's 6 month PhD review. Title TBA
Abstract: TBA
Wednesday Jun 24, 11:30
Chris Curtin ()
Student Review: Chris Curtin 6-month review
Wednesday Jun 24, 15:30
Dr. Elisabete da Cunha (CAS)
Colloquium: Department of Physics and Astronomy Colloquium
Abstract: The spectral energy distributions (SEDs) of galaxies contain important signatures of the physical processes that shape their evolution. Multi-wavelength observations spanning the full ultraviolet to radio spectral range are becoming available not only for local galaxies, but also for samples of increasingly high redshift galaxies, thanks to deep observations with e.g. the Hubble, Spitzer, and Herschel space telescopes, and the Atacama Millimetre Array (ALMA). In order to understand these observations in the context of galaxy evolution theories, we use SED models that translate the observed light into physical properties such as stellar mass, star formation rate, metallicity, and dust content. While these models have been extensively calibrated and applied to local galaxy samples, they are only now starting to be used to understand galaxies in the young Universe. In this talk I will review the main ingredients of spectral energy distribution models and I will describe recent and ongoing developments that are implemented to make the models applicable at high redshifts. I will focus specifically on: (i) recent updates on the spectral evolution of young stellar populations; (ii) self-consistent modelling of the nebular emission of galaxies, and how this affects the broad-band SEDs; (iii) challenges in parameterizing the star formation histories of galaxies, and why they matter; (iv) progress in modelling the contamination by active galactic nuclei (AGN); and (v) how to account for ‘cosmological effects’ when modelling galaxy SEDs at high redshifts.

Speaker: Dr Elisabete da Cunha has been a post-doctoral researcher at the Centre for Astrophysics and Supercomputing since November 2014. She obtained her PhD in 2008 from the University of Paris VI (France) followed by post-doctoral appointments at the University of Crete (Greece) and the Max Planck Institute for Astronomy (Germany). The main focus of her research is galaxy evolution, particularly the development and application of models to measure the physical properties of galaxies from large multi-wavelength surveys. Dr da Cunha is also currently working as project manager of the Taipan survey, a new spectroscopic survey of the southern sky starting in 2016 at the Australian Astronomical Observatory.

http://astronomy.swin.edu.au/staff/edacunha.html
Tuesday Jun 23, 11:30
Srdan Kotus ()
Student Review: Srdan Kotus 18 month review
Thursday Jun 18, 11:30
Erik Tollerud (Yale University)
Colloquium: Local Dwarf Galaxies and Near-Field Cosmology in ΛCDM
Dwarf galaxies are a frontier for new discoveries in both galaxy formation and cosmology. I will discuss work centered around connecting LCDM and its predictions to observations of dwarf galaxies at three different scales of "dwarf". I will discuss the Milky Way and M31's satellites and both solutions and lingering troubles with their abundances and scalings. I will also describe efforts to use these scalings in conjunction with simulations to constrain if and how the satellite's baryons are strongly influenced by their hosts. Finally, I will describe searches for comparable satellites beyond the Local Group, and compare their abundances and properties to straightforward LCDM expectations.
Tuesday Jun 16, 15:30
Luca Rossi (Swinburne)
Student Review: 18 month review - Luca Rossi
18 month review
Thursday Jun 11, 11:30
Laura Wolz (Melbourne University)
Colloquium: Measuring the Large Scale Structure with Intensity Mapping: Foreground Subtraction and Power Spectrum Analysis
Abstract: Intensity mapping of the neutral hydrogen is a new observing technique designed to efficiently map the large scales of the matter distribution in our Universe since hydrogen closely traces the dark matter. The flux of the redshifted 21cm emission is measured on low resolution without identifying individual galaxies such that the clustering behaviour of the cosmic web is still preserved and cosmological analysis, for instance, Baryon Acoustic Oscillation measurements are feasible. Intensity mapping experiments can be conducted by single dish radio telescopes such as Parkes or by interferometric arrays as with the Square Kilometre Array (SKA). In both cases, the observations face significant challenges by instrumental uncertainties and foreground contaminations by our own Galaxy. In my talk, I give an introduction into intensity mapping theory and I review recent efforts and developments in the field. Furthermore, I revise various foreground removal techniques with focus on the independent component analysis. I present showcases of foreground subtraction systematics for future SKA observations, and also the latest results of an analysis of intensity mapping data taken by the Green Bank telescope.
Wednesday Jun 10, 15:00
Rebecca Allen (Swinburne)
Student Review: 30 month review
Thursday Jun 4, 11:30
Franz Kirsten (Curtin)
Colloquium: Pulsar astrometry with VLBI: from classical to extreme
The proper motion and, in particular, the distance of pulsars are typically only poorly constrained. Both parameters are, however, essential to perform, e.g., high precision tests of general relativity or tests of pulsar formation and spin down models. For the majority of pulsars very long baseline interferometry (VLBI) provides the only means to measure both the parallax and transverse motion with high accuracy in a short amount of time. In the first part of my talk I will discuss VLBI observation of the pulsars in the globular cluster M15 which, amongst other things, led to the discovery of geodetic precession in the double neutron star binary M15C. Furthermore, I will present the results of VLBI observations of the three isolated pulsars B1929+10, B2020+28, and B2021+51 aimed at determining their birth locations.
In the second part I will introduce the concept of pulsar scintillometry which allows us to achieve pico-arcsecond astrometric accuracy -- the key to map out the emission region of pulsars.
Friday May 29, 11:30
Busola Alabi ()
Student Review: 18 month review
Wednesday May 27, 15:30
TBC ()
Colloquium: Department of Physics and Astronomy Colloquium
Thursday May 21, 11:30
KG Lee (MPIA)
Colloquium: Mapping the z>2 Cosmic Web Using 3D Ly-a Forest Tomography
Abstract:
The hydrogen Ly-a forest absorption in the high-z intergalactic medium (IGM) has traditionally been studied using bright quasars, but by pushing the limits of existing facilities we are able to exploit faint star-forming galaxies (LBGs) as background sources. Since LBGs have very high area densities (~0.5 per arcmin2 or ~1-2 Mpc/h transverse separations), we are able to perform 3D tomographic reconstructions to map out the large scale structure traced by the foreground IGM. I will describe our recent pioneering observations using this technique, and outline upcoming prospects for studying galaxy evolution and cosmology.
Thursday May 14, 11:30
Raul Jimenez (University of Barcelona)
Colloquium: Fundamental physics and observations of the Universe.
Abstract:
Observations of the cosmos provide a valuable tool to study the fundamental laws of nature. The future generation of astronomical surveys will provide data for a sizeable fraction of the observable sky. These rich data set should provide the means to answer fundamental questions: what are the laws of physics at high energies in the Early Universe? what is the nature of neutrinos? what is the dark matter? what is the dark energy? why are there baryons at all? In this talk I will review the current status, provide a roadmap for future prospects and discuss in detail how we might approach the task of extracting information from the sky to answer the above questions.
Tuesday May 12, 11:30
Giulia Savorgnan ()
Student Review: Giulia Savorgnan's 30 month PhD review: Spitzer and black holes
Thursday May 7, 11:30
Richard McDermid (Macquarie University)
Colloquium: Star Formation Histories and Varying IMF of Early-Type Galaxies from Atlas3D
Abstract: The Atlas3D Survey comprises spatially-resolved spectroscopic data for a complete, volume-limited sample of 260 early-type galaxies observed within the local 40 Mpc volume. This K-band selected sample spans a range in mass from 10e10 to 10e12 solar masses, and probes two orders of magnitude in local galaxy density, giving a large range in mass and environment. Our integral-field spectroscopy covers on average more than one effective radius, providing a complete picture of most of the stellar content of these objects. I will present recent results analysing the global star formation histories of these objects as a function of mass and environment, and explore evidence for a systematically varying IMF normalisation as derived from a combined dynamics and stellar population approach.
Tuesday May 5, 11:30
Andrew Johnson ()
Student Review: Andrew Johnson 30-month PhD review
Thursday Apr 30, 11:30
Fabian Jankowski ()
Student Review: Fabian Jankowski's 18-month review
Wednesday Apr 29, 15:30
TBC ()
Colloquium: Department of Physics and Astronomy Colloquium
Department of Physics and Astronomy Colloquium
Thursday Apr 23, 11:30
Ilya Mandel ()
Colloquium: Beautiful binaries: from Black holes to Tidal disruptions via Exoplanets
Abstract: In this talk, I will discuss recent advances in probing binaries at a variety of scales: (i) prospects for exploring the astrophysics of massive stellar binaries with gravitational-wave observations of the mergers of their compact remnants; (ii) the applications of astrostastics to exoplanet populations; and (iii) the promise of double tidal disruptions of stellar binaries by massive black holes to explain some very intriguing observational signatures from galactic nuclei.
Tuesday Apr 21, 11:30
Toby Brown ()
Student Review: Toby Brown's 18-month review
Thursday Apr 16, 11:30
Megan Johnson (ATNF)
Colloquium: Blasting Away a Dwarf Galaxy: The "tail" of ESO 324-G024
ESO 324-G024 is a gas-rich dwarf irregular galaxy in the Centaurus A (Cen A) Galaxy Group.
It is at nearly the same distance as NGC 5128, which is the S0 host galaxy of the radio source,
Cen A. ESO 324-G024 has a striking HI morphology with a long, ~2.5 kpc extension that
stretches away from the center of NGC 5128 and lies in projection against the northern radio lobe
of Cen A. Because of its proximity and HI morphology, ESO 324-G024 appears to reside
*inside* the northern radio lobe of Cen A. However, we see no signs of depolarization in 20
cm or 6 cm radio continuum observations of Cen A at the location of ESO 324-G024 and
conclude that it is most likely behind the northern radio lobe. In addition, we determine that
ram pressure is the most probable mechanism responsible for creating the HI tail in ESO 324-
G024. If situations such as this are common to all radio galaxies, then ESO 324-G024 may
offer insights into galaxy assembly and growth.
Tuesday Apr 14, 11:30
Pierluigi Cerulo ()
Student Review: Pre-viva talk: The Build-up Of The Red Sequence in High Redshift Galaxy Clusters
Clusters of galaxies are the most massive virialised cosmic structures. The diversity of their environmental conditions, from the dense cores to the sparse outskirts, allows them to be used as observational laboratories for the study of the environmental drivers of galaxy evolution. Furthermore, clusters host the widest range of galaxy masses, from giant ellipticals to dwarf spheroids.
I present the results from the studies of the build-up of the red sequence and of the morphological transformation of galaxies in a sample of 9 clusters at 0.8The comparison with the z~0.05 clusters of the WINGS survey shows that the cluster red sequence was already assembled at z~1 down to magnitudes V=-19.0 mag with no deficit of galaxies at the faint end. We find that unlike nearby clusters, in which S0 galaxies become the most frequent type on the red sequence at magnitudes V>-21.0 mag, the HCS red sequence is dominated by elliptical galaxies at all luminosities. Interestingly, the bright end of the red sequence (V<-21.0 mag) is dominated by ellipticals at low and high redshift. Our results suggest that the cluster red sequence underwent a fast build-up as a consequence of the enrichment from quiescent (preprocessed) galaxies accreted with satellite groups on to a main proto-cluster at z>2.
Our analysis supports the notion that elliptical and S0 galaxies follow different evolutionary paths, with the latter being the result of the morphological transformation of quiescent disc galaxies on the red sequence. I discuss possible scenarios for the evolution of the red sequence in high redshift clusters and for the relations between red sequence build-up and morphological transformations in dense environments.
Thursday Apr 9, 11:30
Lyndsay Old (University of Nottingham)
Colloquium: How well can we measure the masses of galaxy clusters using galaxies as tracers?
With current and future wide field surveys such as the Dark Energy Survey, eROSITA and Euclid predicted to detect hundreds of thousands of galaxy clusters, we have the potential to dramatically increase cosmological constraints from galaxy cluster surveys. Though a variety of techniques exist to detect clusters, their masses cannot be directly measured, but only indirectly inferred from observed properties that are correlated with mass. To maximise the constraining power of clusters for upcoming surveys, it is essential to characterise the level of scatter and systematic bias associated with these mass proxies. In this talk I will present new results on the outcome of an extensive blind study, The Galaxy Cluster Mass Reconstruction Project, which was created in order to ascertain how accurately we can measure cluster masses using techniques that rely upon the positions, velocities, colours and magnitudes of galaxies. I will describe the impact of various member galaxy selection procedures on the final mass estimate, focusing on the friends-of-friends, phase space and red sequence -based approaches. I will then explore the accuracy of a diverse set of galaxy-based mass estimation techniques: velocity dispersion, caustic, richness, abundance matching and radial -based methods. Finally, I will address the implications of the magnitude of scatter in the recovered masses for future cosmological surveys relying on cluster masses.
Thursday Apr 2, 11:30
Sarah Sweet (ANU)
Colloquium: An adaptive optics view of the morphological evolution of galaxies during 1 < z < 2
While local galaxies fall into two dominant populations (passive, red, pressure-supported spheroids, and blue, star-forming disks), these familiar Hubble-type classifications do not apply as readily to high-redshift galaxies, the most massive of which are compact and red. Logically, these high-z galaxies likely become the elliptical population at z=0, but they must grow by 3-5 times in size in the interim. It is proposed that the size evolution of galaxies either occurs by accretion of smaller galaxies, whereby the compact core remains, or by adiabatic expansion due to mass-loss winds, whereby the entire galaxy expands. The key to distinguishing between these two scenarios is the accurate measurement of the size-mass relation. This requires sufficient resolution to measure effective radii and Sersic indices of the most compact galaxies over a wide field of view, at rest-frame optical wavelengths to avoid bias due to small-scale localised star-formation.
In this talk I will describe our project using the Gemini South Adaptive Optics Imager, with its unique capability of diffraction-limited near-infrared wide-field imaging, to image the cores of galaxy clusters over the redshift interval 1 < z < 2. I will present our results from the first galaxy cluster, as well as our methodology for processing the complex data from this new instrument (including successful correction for the quasi-static off-axis distortion, varying PSF and image ghosting).
Tuesday Mar 31, 11:30
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Student Review: Emily Petroff's 30-month review
Thursday Mar 26, 11:30
Jing Wang (CSIRO ATNF)
Colloquium: Searching for Footprints of Gas accretion in Disk galaxies
Most galaxies in the local universe evolve in the secular mode, and the processes are almost always accompanied by obtaining or losing of cold gas. The brightest cluster galaxies (BCG) are as old as galaxies of the same stellar masses, suggesting that the location of centre of dark matter halo does not guarantee gas accretion.
Even the most extreme HI-rich galaxies exhibit regular morphologies, suggesting that the gas accretion is happening in a slow and gentle way.
The correlation between the color gradients and gas fraction in star-forming disk galaxies supports the picture of cosmological gas accretion (as a necessary supplement to fountain mechanism). The gas ``conformity'' phenomenon for central and satellite galaxies supports the picture of cold accretion in galaxies with intermediate masses. Gas accretion may drive the inside-out disk formation in two ways: directly forming the outer disks, and suppressing the growth of central mass concentration by suppressing bars.
Wednesday Mar 25, 15:30
Jeff Davis (CQOS)
Colloquium: Department of Physics and Astronomy Monthly colloqium
Title: Developing the tools to unlock Nature's secrets.

Abstract: Understanding the mechanisms driving complex phenomena in both natural and manmade systems is a requirement for reliably mimicking and utilising such processes in device applications. One such process is how energy is transferred within and between light-harvesting complexes involved in natural photosynthesis. To resolve these mechanisms we have developed a suite of techniques that utilise femtosecond laser pulses to explore the dynamics and quantum mechanical pathways that characterise them.

I will describe some of these techniques and the understanding we have been able to acquire by applying them to complex systems from coupled semiconductor quantum wells to photosynthetic light harvesting complexes.
Tuesday Mar 24, 11:30
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Student Review: Vivek Venkatraman Krishnan's 6-month review
Monday Mar 23, 15:00
Giorgos Vernardos (Swinburne)
Colloquium: Data Intensive Quasar Microlensing
Quasar microlensing is a unique probe of quasar structure, from the broad emission line region down to the accretion disc and the supermassive black hole. Moreover, it can be used to study the mass distribution of the galaxy-lens and perform measurements of Hubble's constant. So far, only single, or small collections, of lensed quasars have been studied using microlensing techniques due to the observational and computational challenges involved. However, this is about to change by the imminent discoveries of the upcoming all-sky survey facilities (e.g. SkyMapper, LSST). I will present results, data, and tools from the GPU-Enabled High-Resolution MicroLensing parameter survey (GERLUMPH). In particular, I will systematically investigate modeling properties across the parameter space, to answer how well we will be able to constrain quasar structure in the future. Moreover, I will demonstrate how our eResearch infrastructure, i.e. database and web interface to TB-sized microlensing simulations, complemented by advanced eTools for an end-to-end online analysis of lensed systems, can accelerate the rate of scientific discovery. Such an online resource would dramatically speed-up the consistent and systematic study of large collections of these systems, using just a web browser at the user end.
Thursday Mar 19, 11:30
Ivy Wong (UWA)
Colloquium: How galaxies stop forming stars ?
Abstract: The Local Universe provides an excellent laboratory for studying the detailed processes of star formation and galaxy evolution. In this seminar, I will present some recent highlights from my work on blue early-type galaxies. Our latest model demonstrate that the observed "Green Valley" can be reproduced by two star formation truncation pathways for the evolution of galaxies. We previously found that the local post-starburst galaxies occupy a well-defined region in the low-mass end of the "Green Valley" and that even though star formation has only recently turned off, their morphology already resemble those of the low-mass red sequence galaxies. Since the post-starburst population is far too evolved, we probed the atomic gas content of its predecessor population, namely, the blue early-type galaxies to search for the smoking gun that caused the sudden truncation of star formation. Our pilot study suggest that a kinetic process (probably AGN feedback) is driving the quick truncation of star formation in these systems, rather than a simple exhaustion of gas supply. In this talk I will also briefly describe some early results from the Radio Galaxy Zoo project.
Thursday Mar 12, 11:30
Cathryn Trott (Curtin)
Colloquium: Estimation of the Epoch of Reionisation Power Spectrum
Abstract:
Fluctuations of the brightness temperature of neutral hydrogen in the early Universe trace conditions in the intergalactic medium during the Epoch of Reionisation (EoR). In this epoch, the first sources of ionising radiation heated and re-ionised the surrounding medium, marking a fundamental change in the Universe. Low-frequency radio telescopes, such as the Murchison Widefield Array (MWA), aim to detect the signal from these neutral hydrogen structures, and estimate their spatial structure over time. However, the weakness of the signal relative to foreground continuum emitters, makes the task a challenging signal processing problem. These sources are observed through the distorting effects of the ionosphere and interplanetary scintillation, and the complications of a chromatic instrument. In this seminar I will introduce the EoR, the expected signal structure and observation of this epoch with radio interferometers. I will then discuss the structure of the foreground sources, the need to better understand their properties, and some of the work we have been doing to address these challenges.
Thursday Mar 5, 11:30
Chiaki Kobayashi ()
Colloquium: Cosmological simulations with AGN feedback
Abstract:
We predict various properties of galaxies and their time evolutions, using our cosmological, hydrodynamical simulations with the feedback from active galactic nuclei (AGN). We have applied a new model for the formation of black holes motivated by the first star formation, in
contrast to the merging scenario of previous works. The model parameters are determined from observational constraints, namely, the cosmic star formation rate history, black hole mass-galaxy mass
relation, and the size-mass relation of galaxies. We then obtain better agreement with the observed down-sizing phenomena, namely, the colour-magnitude relation, specific star formation rates, and the \alpha enhancement of early type galaxies. In massive galaxies, the AGN-driven outflows transport metals into the
intergalactic medium, which sometimes result in external enrichment in smaller galaxies. Nonetheless, these metallicity changes are negligible, and the mass-metallicity relations, which are mainly
generated by supernova feedback at the first star burst, are preserved. These AGN-driven outflows are important for a large-scale chemical enrichment in the Universe, distributing metals in the
circumgalactic medium and the intergalactic medium. In particular, we find selective mass-loss where iron is more effectively ejected than oxygen because of the time-delay of Type Ia Supernovae. Our simulations enable us to predict spatial distribution of heavy elements within galaxies. Metallicity radial gradients can be affected by AGN feedback, but are more sensitive to their merging histories. We find weak correlation between the gradients and galaxy mass, which is consistent with observations, and supports the
formation scenario in which galaxies are formed through dissipative merging of galaxies with various masses in the cosmological context.
Thursday Feb 26, 11:30
Peter Wizinowich ()
Colloquium: Adaptive Optics at W. M. Keck Observatory -- Peter Wizinowich
Abstract: The first natural guide star (NGS) and laser guide star (LGS) adaptive optics (AO) systems on 8 to 10 m class telescopes were implemented on the Keck II telescope in 1999 and 2004, respectively. Both Keck telescopes are now equipped with LGS AO systems and 558 refereed science papers have been published using data from these systems through 2014. The speaker will provide a brief overview of the Keck telescopes and instrumentation, and then focus on the current and planned AO capabilities and the resultant science.
Wednesday Feb 25, 15:30
David Wilner (Harvard CfA)
Colloquium: Dept. colloquium: New Views of Planet-Forming Disks with Millimeter Interferometry
Title:
New Views of Planet-Forming Disks with Millimeter Interferometry

Abstract:
The circumstellar disks that naturally arise from the star formation process are the sites where planets are made. Many hundreds of these analogs to the disk that spawned our Solar System are nearby and accessible to detailed investigation. Millimeter interferometers provide direct access to the cool material in these disks, enabling resolved observations of dust morphology and properties, as well as the thermal, chemical, and dynamical structure of gas, all of which impact what kind of planetary systems, if any, may form (or may be forming now). I will review studies from the Submillimeter Array on Mauna Kea that illustrate key phenomena, including disk density structures and the demographic effects of stellar host mass and multiplicity, and I will touch on some incredible advances that are now beginning with the revolutionary capabilities of the Atacama Large Millimeter Array.
Friday Feb 20, 10:00
Alberto Pepe ()
Colloquium: Special colloquium: Data-driven, interactive scientific articles in a collaborative environment with Authorea
Abstract:
Most tools that scientists use for the preparation of scholarly manuscripts, such as Microsoft Word and LaTeX, function offline and do not account for the born-digital nature of research objects. Also, most authoring tools in use today are not designed for collaboration, and, as scientific collaborations grow in size, research transparency and the attribution of scholarly credit are at stake. In this talk, I will show how the Authorea platform allows scientists to collaboratively write rich data-driven manuscripts on the web --- articles that would natively offer readers a dynamic, interactive experience with an article’s fulltext, images, data, and code --- paving the road to increased data sharing, data reuse, research reproducibility, and Open Science.
Thursday Feb 19, 10:00
Lisa Kewley (ANU)
Colloquium: CANCELED!!!
Abstract: TBA
Friday Feb 13, 11:30
Mike Hudson ()
Colloquium: The Evolution of Galaxies and their Dark Matter Halos from Weak Gravitational Lensing
Abstract:
Galaxy formation is inefficient: at best 25% of the available baryonic material is converted into stars. Yet these stars are what observers see. Theorists, on the other hand, have no trouble with modelling dark matter and its evolution in the LCDM framework, but of course dark matter is invisible. I will describe how weak lensing now allows one to "observe" dark matter (at least in a statistical sense). I will focus on the problem of how galaxies grow both their stellar and their dark matter content, and how the current state-of-the-art survey, CFHTLenS, has revealed a new way of looking at galaxy evolution.
Thursday Feb 5, 11:30
Sirio Belli ()
Colloquium: Exploring the evolution of the red sequence with deep Keck spectroscopy -- Sirio Belli
Abstract: The most effective probe of the physical nature of quiescent galaxies is absorption line spectroscopy, which is particularly challenging at high redshift. Using the improved sensitivity of optical and infrared detectors at the Keck observatory, and the multiplex advantage of its new MOSFIRE spectrograph, we have undertaken a new spectroscopic survey in the redshift range 1 < z < 2.5. Velocity dispersions and stellar ages derived from our spectra, together with HST-based sizes, provide valuable insight into the mass assembly of quiescent galaxies. We find that the stellar to dynamical mass ratio evolves with redshift, which might imply a change in the dark matter fraction or in the stellar initial mass function. Our main conclusion is that the population of compact quiescent galaxies at high redshift grows in size partly via minor mergers (physical growth) and partly because of the increasing contribution of recently quenched, larger galaxies (progenitor bias). Finally, by fitting stellar population models to the spectroscopic and photometric data, we are able to robustly constrain, for the first time, the mass assembly and star formation histories of z > 2 quiescent systems.
Thursday Jan 29, 11:30
Michele Trenti (Uni Melbourne)
Colloquium: Galaxies at Cosmic Dawn
Abstract:
Recent Hubble's near-IR observations transformed our view of early galaxy formation by building reliable samples of galaxies out to redshift z~8 (~700 Myr after the Big Bang) and hinting at a dramatic evolution in properties at yet earlier times. From z~8 to z~10 (~200 Myr) the luminosity density seems to decrease by a factor ten, but bright galaxies may remain relatively common based on a handful of bright (m<27) sources detected in legacy fields (GOODS/CANDELS). I will present our existing observations at z~8-10 and combine them with spectroscopic followup data and with the measurement of the two point correlation function at z>7 to discuss the connection between dark-matter halos, assembly of galaxies, and production of reionizing photons during cosmic dawn.
Finally, I will preview the first observations from the new extra-large (32 days) Brightest of Reionizing Galaxies (BoRG) HST survey, designed to find the most luminous z~9-10 sources accessible before the next generation of IR space telescopes.
Thursday Jan 22, 11:30
Ixandra Achitouv (Swinburne)
Colloquium: Abundance of halos and voids in the excursion set approach - Ixandra Achitouv
Abstract:
Our picture of the present universe is mainly composed of voids and dark matter halos, the building blocks of cosmic structure. The halo mass functions quantifies their number density as function of mass, and it is a key to predicting several large-scale structure observables. In this talk, I will review the lastest theoretical advancements on the derivation of a halo mass function which encodes physical aspects of the halo process and is capable of reproducing numerical N-body simulation results with unprecedented accuracy.