Skip to Content

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
  2017    2016    2015    2014    2013    2012    2011    2010    2009    2008    2007    2006    2005    2004    2003    2002    2001    2000   

2013 Colloquia

Tuesday Dec 17, 11:30
Guido Moyano Loyola (Swinburne)
Student Review: Guido Moyano Loyola 30-month review
Monday Dec 16, 15:30
S. G. Djorgovski (Caltech)
Colloquium: Exploration of the Time Domain with the Catalina Real-Time Transient Survey
The time domain has become one of the most vibrant and trendy areas of astrophysics, touching on subjects ranging from the Solar system to cosmology and extreme relativistic phenomena. I will address exploration of the time domain in a more general context, describe briefly the current state of the CRTS survey and some of the results from it, and the challenge of automated classification of transient events and variable sources.

Thursday Dec 5, 11:30
Syed Uddin (Swinburne)
Student Review: Syed Uddin
18 month PhD thesis review.
Friday Nov 29, 11:00
Roberto Abraham (University of Toronto)
Colloquium: Ultra-low Surface Brightness Imaging with Project Dragonfly
Abstract: I will describe early results from Project Dragonfly, a Toronto/Yale instrument concept whose goal is to open up the new observational regime of ultra low surface brightness astronomy at visible wavelengths. Its design is optimized for testing the most fundamental prediction of galaxy formation models, namely that at low surface brightness levels all galaxies are embedded within a sea of complex substructure. The project couples innovative observing techniques (multiple redundant unobstructed beam paths and real-time modeling of sky variations for precision control of systematics) with new technologies, such as sub-wavelength nano-fabricated optical coatings to minimize scattered light and ghosting.
Thursday Nov 28, 11:30
Giorgos Vernardos (Centre for Astrophysics & Supercomputing)
Student Review: Gravitational microlensing and the quasar galaxy connection on gSTAR
30-month review
Tuesday Nov 26, 11:30
Bernard Meade (Swinburne University)
Student Review: TBD
6-month review talk
Thursday Nov 21, 11:30
Gerhardt Meurer (ICRAR)
Colloquium: The Good and Stable Life of Disk Galaxies
Abstract: Our universe has passed the peak of star formation activity. Galaxies
are accelerating away from each other, and their evolution is becoming more dominated by secular proceses. Indeed, observations show that galaxy disks have reached an equilibrium stability throughout their optically bright portions and beyond. I will show that the assumption of a uniform stability provides a good model for the structure of present day disk galaxies. It allows us to resolve some long known puzzles and provides a bridge between star formation, the gas and dark matter within galaxies. I will describe our current work on the constant stability disk models and prospects for understanding the main-sequence of star forming galaxies and their evolution.
Friday Nov 15, 12:30
Chris Tinney (UNSW)
Colloquium: The Giant Magellan Telescope Project - An Update
Abstract: The GMT will be the first of the world's next generation of Extremely Large Telescope to go into operation, and Australia has committed funds to be a 10% member of this exciting major project. I will update members of the astronomical community on progress in the telescope's development and its instrumentation.
Thursday Nov 14, 11:30
Ariel Sanchez (MPE)
Colloquium: Cosmological implications of the clustering of galaxies in BOSS
Abstract: Driven by the potential of large-scale structure (LSS) observations to shed light on the physics behind the accelerated expansion of the Universe, several ground-breaking galaxy surveys are currently under way. These surveys will measure the LSS of the Universe with unprecedented precision, providing new insights not only on the origin of cosmic acceleration, but also on many other important physical parameters. The ongoing Baryon Oscillation Spectroscopic Survey (BOSS) is an example of these new surveys. In this talk I review the cosmological implications of the large-scale galaxy clustering in BOSS, with an emphasis on the problem of cosmic acceleration.
Tuesday Nov 12, 11:30
Helga Denes (Swinburne)
Student Review: Helga's 30 month review
Thursday Nov 7, 10:30
Rob Bassett ()
Student Review: Rob Bassett 19 month review
Wednesday Nov 6, 11:00
Marc Davis (UC Berkeley)
Colloquium: Large Scale Structure -- Cosmic Flows
Abstract: 20 years ago, Cosmic Flows was an active research field that abruptly ended when two methods did not agree on conclusions. Since that time the data, with enormous input from Australian astronomers, has recently improved, justifying another look. The velocity field generated by the galaxy distribution out to 12,000 km/s explains our dipole velocity of 640 km/s and the peculiar velocity of all nearby galaxies. This talk will be instructive for the younger students who are not familiar with 20 years of research, and for the other old-timers, it is quite beautiful to see how well linear theory fits the observed velocity field.
Thursday Oct 31, 11:30
Randall Wayth (Curtin)
Colloquium: GLEAM: The MWA all-sky survey
Abstract: The extraordinary field of view of the Murchison Widefield Array (MWA) gives it impressive survey capabilities. The GaLactic and Extragalactic All-sky MWA (GLEAM) survey will cover the entire sky visible to the MWA between 80 and 230 MHz, yielding a comprehensive census of the low frequency radio sky. GLEAM will enable study of a wide range of astrophysical objects, from the very small (pulsars and their wind nebulae) to the very large (cosmic ray acceleration mechanisms in galaxy clusters, the cosmic web). Local to our Galaxy, GLEAM will open a new window to study Galactic magnetism, supernova remnants and the interstellar medium. In this talk I will give an overview and update of MWA operations, review the MWA key science programs and the details of GLEAM and GLEAM-based science programs.
Tuesday Oct 29, 11:30
Student Review: Elodie Thilliez's 6 month review
Thursday Oct 24, 11:30
Themiya Nanayakarra ()
Student Review: Themiya Nanayakarra-6 month PhD student review
Wednesday Oct 23, 11:30
Director candidate #3 ()
Colloquium: CAS colloquium
Tuesday Oct 22, 14:30
Director candidate #2 ()
Colloquium: CAS colloquium
Tuesday Oct 22, 11:30
George Bekiaris ()
Student Review: George Bekiaris PhD student review
Monday Oct 21, 14:00
Director candidate #1 ()
Colloquium: CAS colloquium
Thursday Oct 17, 11:30
Daniela Carollo (Macquarie)
Colloquium: The Halo System of the Milky Way and the CEMP Stars Connection
Abstract: Carbon Enhanced Metal Poor stars (CEMPs) have been recognized to be an important stellar component of the halo system of the Milky Way. They contain crucial information on the nature of the nucleosynthesis in the early Galaxy. In this talk I will discuss the general properties of the CEMP stars and their importance in Near Field Cosmology. I will also summarize the current view of the nature of the Galactic stellar halo, which comprises at least an inner- and an outer-halo population, each with different kinematics, spatial distributions, and chemistry, as confirmed both from recent observations and numerical galaxy formation scenarios. These smooth halo components exhibit also a distinct chemical pattern in term of fraction of CEMP stars. Such characteristics will be discussed during this talk together with possible formation scenarios of the halo system.
Tuesday Oct 15, 11:30
Antonio Bibiano ()
Student Review: 6 Month Review
Monday Oct 14, 15:00
Frazer Pearce (Nottingham)
Colloquium: Special Colloquium - Full Euclid Simulation
The Euclid satellite is a medium class space mission designed to measure the expansion of our Universe to explore the nature of dark matter and dark energy. In order to achieve this the observational data will have to be compared to theoretical models of unprecedented size, accuracy and stabilty. I will discuss the preparation of these mock observations, from initial condition generation to production simulation via a range of techniques to post-processing and the generation of mock galaxy catalogues.
Thursday Oct 10, 11:30
Paola Oliva ()
Student Review: Paola Oliva 18-month PhD review
Tuesday Oct 8, 11:30
Mark Durre (Swinburne)
Student Review: Mark Durre 6 month review
Thursday Oct 3, 11:30
Pablo Galaviz (Macquarie University)
Colloquium: Binary Black Hole mergers in f(R) theory
Abstract: Alternative gravitational theories are candidates to solve some of the cosmological and astrophysical puzzles like the dark matter and dark energy problems. Particularly, f(R) gravitational theory is a useful toy-model to test some of the modifications of Einstein's theory. From solar system observations and Eöt-Wash experiments it is possible to set constraints the theory in the weak-field regime. However, the main effect of f(R) theory involves strong gravitational fields. On the other hand, in a near future gravitational wave detectors will bring us a new way to constraint the alternative gravitational theories. Collision of black holes are the most promising sources of gravitational waves. The waveforms generated by collision of black holes can give us a way to confirm or discard the f(R) theory in the strong gravitational regime. In this talk I will review the mathematical background related to f(R) gravity and the numerical technique necessary to model the collision of black holes. I will present numerical results related to the characterisation of the gravitational waves generated by binary black hole collision in the f(R) theory of gravity.
Tuesday Oct 1, 11:30
Ivan Minchev (Potsdam)
Colloquium: Constraining the formation and evolution of galactic discs through numerical modeling
Abstract: I will discuss various galactic dynamics problems related to our understanding of the formation and evolution of disc galaxies. It will be demonstrated that if radial migration is indeed responsible for the formation of extended galactic discs, then they must be kinematically hot because of the approximate conservation of stellar radial and vertical actions. While contributing to disc thickening in the disc outskirts, radial migration will be shown to have minimal effect at intermediate radii (R<3-4 scale-lengths), thus unable to explain the formation of thick discs. Finally, a new method for modeling the chemo-dynamical evolution of galactic discs will be introduced. Focusing on the Milky Way, I will show that this model is consistent with nearly all currently available data and will outline a number of predictions for forthcoming large-scale spectroscopic surveys.
Friday Sep 27, 11:30
Chris Churchill (University of New Mexico)
Colloquium: The Self Similarity of Galactic Gaseous Halos: Clues to the Evolution of Galaxies
Abstract: We present the reasoning behind why the circumgalactic medium (CGM)
surrounding galaxies is dominant regulatory medium for governing galaxy evolution. We then describe results from a large sample of z<1 galaxies for which the halos are probed using MgII absorption. These data indicate that the cool/warm CGM scales self-similarly with halo mass (dark matter + baryons). Interpretations and deeper insight require two new avenues: (1) studies of galaxy simulations to examine the connection between stellar formation and feedback, the CGM, and IGM accretion, and (2) a comprehensive analysis of both the hot, high-ionization CGM and the cool, low-ionization CGM components. For the former, we describe preliminary work and results. For the latter, we describe a coming Large HST program using the COS spectrograph. We highlight the expected outcomes of such studies.
Thursday Sep 26, 11:30
Sreeja Kartha ()
Student Review: Sreeja Kartha 30-month review
Friday Sep 20, 11:30
Sara Ellison (University of Victoria)
Colloquium: Galaxy mergers in the nearby universe
Abstract: Galaxy mergers are known to trigger dramatic changes in galactic morphology, metallicity, star formation and black hole accretion rates. However, the extent to which these properties respond to the interaction can vary greatly both between different mergers, and at different times during a given interaction. In order to piece together a complete view of the changes that galaxies undergo during the interaction processes, we have been undertaking a large, multi-faceted investigation of galaxy mergers in the nearby universe. We have combined a large sample of galaxy pairs that span projected separations from a few kpc out to a Mpc, with a sample of post-mergers, all selected from the Sloan Digital Sky Survey (SDSS). Over such a separation range, this sample can be used to trace the galaxy merger population throughout their encounter in a homogeneous and statistically meaningful way. I will present the results from a series of papers on these merger results, which investigate many facets of the merger, including triggered star formation, accretion onto the central supermassive black hole and changes in galactic chemistry.
Thursday Sep 19, 11:30
Michael Brown (Monash)
Colloquium: Galaxy Spectra and Recolouring the Universe
Distances and luminosities are crucial for understanding celestial objects. For galaxies beyond the local Universe, the observed wavelengths and desired rest-frame wavelengths may differ significantly, so models are needed to determine rest-frame galaxy properties from observed galaxy properties. Unfortunately, many of the commonly models of galaxy spectra have significant systematic errors, and these cause large errors in measurements of galaxy luminosities, colours and distances. I have led a collaboration of international astronomers to produce a new atlas of 120 galaxy spectra spanning from ultra-violet through to infrared wavelengths, combining imaging and spectroscopy from satellites and ground-based telescopes. Our atlas has a far larger sample size, broader wavelength coverage and smaller systematic errors than similar works in the prior literature. I will provide illustrations of how the atlas has been utilised by Monash PhD students and postdocs, significantly changing the measured colours of low redshift galaxies and identifying hidden star formation in red galaxies.
Wednesday Sep 18, 12:00
Student Review: Mark Hutchison's 6 month review
**Note change of time! **
Friday Sep 13, 11:30
Pamela Gay (Southern Illinois University Edwardsville)
Colloquium: Moon Mapping: Understand the accuracy of science done by hand
Abstract: While astronomy and planetary science both endeavor to be sciences that are based on well-defined measurements, there are still many areas of ambiguity where machine measurements are possible and the human eye and mind must be used. These tedious tasks are becoming less tractable as automated surveys and orbiting space craft generate a flood of data. In order to try accomplish more science at a time when resources are less, many scientists are turning to volunteers in the public for help. From visual identification of galaxy morphologies to counting of craters on the moon, citizen scientists are now helping professional scientists accomplish complex tasks. In this talk, Dr. Gay will examine the best practices in engaging citizen scientists, and how to detail the accuracy of their work (and the work of professional scientists) through software that can group multiple individual's mappings of one field to derive both an average map and errors. The Moon Mappers citizen science project will be presented as a detailed case study, and an analysis of measurement error from both professional and volunteer mappers will be discussed along with early science results for the Apollo 15 region.
Thursday Sep 5, 11:30
Jesus Falcon Barroso (Instituto de Astrofisica de Canarias)
Colloquium: The stellar angular momentum across the Hubble Sequence: a tale from different IFU surveys
Abstract: In this presentation I will give an overview of the stellar angular momentum of galaxies across the Hubble sequence as observed by the ongoing CALIFA Survey. I will present a morphologically unbiased account of the stellar angular momentum distribution in ~200 nearby galaxies, and compare it with the Atlas3D Survey of early-type galaxies. As the CALIFA Survey at the same time includes lenticular and spiral galaxies, we are in the unique position to (dis)prove whether lenticular galaxies are kinematically compatible with being faded spiral galaxies. In fact we have found a group of spiral galaxies where this scenario does not hold. I will report what is so special about this group of galaxies and possible paths for the formation and evolution across the Color-Magnitude diagram.
Thursday Aug 29, 11:30
Adam Stevens ()
Student Review: 6 Month Review
Tuesday Aug 27, 11:30
Student Review: Pierluigi Cerulo 30 month review
Tuesday Aug 13, 11:30
Luis Torres ()
Student Review: Luis Torres 6-month review
Thursday Aug 8, 11:30
Dr. Gabor Worseck (Visiting Fellow, Swinburne) (Max Planck Institute for Astronomy (Heidelberg, Germany))
Colloquium: Mapping the Reionization History of Helium with HeII Lyman Alpha Absorption Spectra
After recombination the Universe was highly neutral until the first UV sources ionized their surroundings. Unlike hydrogen, which was reionized by the first stars at redshifts z>6, the full reionization of helium had to await the advent of quasars capable of producing the required hard photons. Like hydrogen, intergalactic singly ionized helium can be probed by Lyman alpha forest spectroscopy of quasars. However, the far UV flux of most high-redshift quasars is extinguished by intervening HI Lyman limit systems. Until recently only a handful of HeII sightlines had been studied in detail with HST. The advent of GALEX and HST/COS have revolutionized studies of HeII reionization. The clear picture emerging is that HeII reionization likely ended at z~2.7, but was highly inhomogeneous and extended. Complementary Keck+VLT spectroscopy of the coeval HI forest maps the density field along the quasar sightline, yielding the first tantalizing evidence for "inside-out" HeII reionization occurring first in overdense regions around quasars. Some of these HeII-reionizing quasars have been identified by us in a dedicated deep imaging and spectroscopic survey.

Bibliographical information:
Gabor Worseck did his PhD at the Astrophysical Institute Potsdam, Germany, and then worked as a postdoctoral research fellow at the University of California Santa Cruz. Currently, he is a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany. His main research interests are the reionization history of the Universe, the physical state of the intergalactic medium and quasar surveys. His research is mainly observational in nature, combining data from the Hubble Space Telescope and ground-based 8-10 meter facilities.
Thursday Aug 1, 11:30
Simona Gallerani (Scuola Normale di Pisa)
Colloquium: Far Infrared Emission Lines in z~6 Quasars and Galaxies
Abstract: Far infrared (FIR) emission lines (e.g. [CII] at 158 micron, [NII] at 205 micron, CO(J-J-1) at 115J GHz) are among the brightest emission lines in most galaxies. They originate in the interstellar medium and represent powerful tools for detecting and characterizing high redshift sources. We present PdBI observations of FIR lines in a lensed quasar at z=4.4. Through the combined detection of the [CII], [NII], and CO(5-4) lines we constrain several properties of the ISM in this object, (i.e. the gas density and metallicity, and the radiation field intensity). Moreover, we detect broad wings of the [CII] line in one of the most distant quasar known (z=6.4). The extent of the wings, and the size of the [CII] emitting region associated to them, are indicative of a QSO-driven massive outflow with the highest outflow rate ever found. Up to now, z>4 detections of FIR lines have been obtained only in galaxies hosting AGN or with high star formation rates. The unprecedented sensitivity of ALMA allows the detection of FIR lines even from “normal” population of high-z galaxies. We adopt radiative transfer simulations to derive the expected intensity of several FIR lines emitted by Lyman Alpha Emitters. We provide the required ALMA observing time for detecting z=6-7 LAEs as a function of their metallicity.
Thursday Jul 25, 11:30
Leon Koopmans (Kapteyn Institute)
Colloquium: Constraints on Dark Matter in Galaxies from Strong Gravitational Lensing: Going from from 10^12 to 10^6 solar masses
Abstract: The evidence for the presence of dark matter on galactic scales is now strong, although some debate remains on its importance in early-type galaxies. I will discuss what we have learned about dark matter in galaxies from strong gravitational lens studies on scales of 1-100 kpc. In particular in combination with stellar dynamics and more recently with stellar population analyses, the study of strong lenses has yielded some remarkable results on the relative contributions of dark and stellar mass inside the effective radii of massive early-type galaxies, shedding as a by-product new light on the shape of the stellar IMF. Besides being able to probe the stellar and dark matter on large and smooth scales, strong gravitational lensing can also probe CDM substructure in galaxies on scales as small as 10^8 solar masses currently. I will show our most recent findings using the technique of gravitational imaging, applied to HST and Keck Adaptive Optics data. Within a decade or less,
this method will allow studies of CDM substructure down to 10^6 solar masses over a wide range of galaxy masses and redshifts, enabling stringent tests of the LambdaCDM paradigm.
Monday Jul 22, 16:00
Rogier Windhorst (ASU)
Colloquium: JWST Seminar
Special Seminar: How will the James Webb Space Telescope measure First Light, Reionization, and
Galaxy Assembly: Science and Project Update as of 2013.

Friday Jul 5, 11:30
Markus Kissler-Patig ( Gemini Observatory Director)
Colloquium: Welterweights in dark space - Intermediate-mass black holes
Abstract: Intermediate-mass black holes, featuring masses of a few hundred to a few tens of thousands solar masses, have recently attracted quite some interest. They fill the gap between solar mass black holes and super-massive black holes and might be at the origin of the formation of the latter. After a decade of controversy, a few reliable intermediate-mass black holes are now known - they appear to lie on the black hole mass - sigma relation defined for super-massive black holes. Coincidence or physical cause? I will review the recent work of our group on intermediate-mass black holes at the centre of Galactic globular clusters and put them into the context of star cluster formation, nuclear clusters and super-massive black holes.

This will be followed by an informal Q+A session about Gemini.
Thursday Jul 4, 11:30
Emily McLinden (University of Texas at Austin)
Colloquium: Studying gas kinematics at z ~ 3.1 with the Lyman-alpha emission line
Abstract: I will present near-infrared spectroscopic measurements of the [OIII] emission line from six z ~ 3.1 Lyman-alpha emitting galaxies (LAEs) as well as similar measurements from multiple subregions of a z ~ 3.1 Lyman-alpha emitting blob (LAB). I will explain how combining such [OIII] detections with the Lyman-alpha measurements we have for these objects allows us to probe the gas kinematics in these objects. This allows us to look for evidence of galactic outflows (and/or inflows) even in these very distant objects. This is an exciting area of study because this type of feedback can have important consequences on both large and small scales - from affecting the evolution of an individual starbursting galaxy to affecting the evolution of the intergalactic medium (IGM) and the reionization of the universe. I'll also briefly discuss the HETDEX project of which I am member, and how this project will contribute to the study of galaxy evolution and gas kinematics in z = 2--4 galaxies.
Tuesday Jul 2, 11:30
Molly Peeples (UCLA)
Colloquium: What have galaxies done with their metals?
Abstract: The eventual fate of a galaxy's metals is a direct tracer of its history of star formation, gas flows, and feedback processes. I will present an accounting of metals made by ~L* galaixes at z=0, showing that the bulk of metals released by supernovae and AGB stars are no longer in galaxies, and are instead in the circumgalactic medium (CGM) or intergalactic medium. The COS-Halos survey has created a statistically-sampled map of the gaseous CGM of low redshift ~L* galaxiesout to impact parameters ~150 kpc using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope. Using this map, I will show that the masses of metals found in the cool (10^4 < T < 10^5 K) photoionized and the more highly ionized OVI-traced CGM could potentially account for all of the metals expelled from ~L* galaxies at z~0.
Thursday Jun 27, 11:30
Yin-Zhe Ma (University of British Columbia)
Colloquium: The cosmic peculiar velocity field
Abstract: The peculiar velocity field is one of the important probes of large scale structure. Its prediction from linear perturbation theory of $\Lambda$CDM should be rigorously tested against observational data. I will lay out a method which can quantify the difference between the predicted velocity field from the density field and therefore directly test the gravitational instability diagram. By applying the hyper-parameter technique, we quantify the magnitude and direction of the bulk flow on scale of 50 Mpc/h, and test its consistency with LCDM prediction. I will present a method which can maximize the cosmological information one can obtain from the bulk flow study.
Tuesday Jun 4, 11:30
Nicola Pastorella (Swinburne)
Student Review: 18 month review
Thursday May 23, 11:30
Annie Huges (MPIA)
Colloquium: Molecular Gas in M51: the PAWS View
Abstract: The structure of the molecular interstellar medium (ISM) on the scale of individual clouds is an important quantity for models of star formation, and one that is often invoked to explain the correlations between tracers of gas and star formation derived from kiloparsec-scale observations of nearby galaxies. In this talk, I will discuss the latest results from our analysis of the structure of molecular gas on ~40pc scales in M51, using new data from the Plateau de Bure Interferometer Arcsecond Whirlpool Survey (PAWS, PI: Schinnerer). We find that the organization of the molecular ISM (as traced by CO emission and quantified through PDFs, GMC mass spectra, clumping factors and Larson's Laws) varies significantly with galactic environment within M51 (arm/interarm/nuclear region), and between M51 and two nearby low-mass galaxies, M33 and the Large Magellanic Cloud. I will highlight some intriguing connections between the properties of the CO PDFs and the properties of M51's young stellar cluster and GMC populations. These suggest that galactic-scale dynamical processes play a significant role in the formation and evolution of GMCs and stellar clusters in galaxies with strong spiral structure like M51.
Thursday May 16, 11:30
Lisa Harvey-Smith (CSIRO)
Colloquium: Update on the Australian SKA Pathfinder
Abstract: CSIRO's Australian SKA Pathfinder (ASKAP) is a radio interferometer in the remote Murchison region of Western Australia, equipped with phased array radio receivers for an ultra-fast survey capability. Whilst the full suite of receivers is still under construction, early engineering test results from only three dishes are giving us tantalising glimpses of things to come. In this talk, I will describe the status of ASKAP, present latest commissioning results and discuss the plans for the commencement of scientific observations. Since last year's decision to co-locate the SKA in Australia and South Africa, the SKA project has made significant progress in producing a baseline design for Phase 1 of the SKA. In this context, I will also discuss the plans to expand ASKAP to form an ultra-fast survey instrument for Phase 1 of the SKA.

Lisa Harvey-Smith is the ASKAP Project Scientist.
Thursday May 2, 11:30
Krzysztof Bolejko (University of Sydney)
Colloquium: The bright and dark side of cosmic voids - a new window into dark matter and dark energy
Abstract: More than half of the volume of our Universe is occupied by cosmic voids. Cosmic voids are regions where matter density is much below the mean density of the Universe. In galaxy surveys they appear as vast empty spaces between filaments, which contain very few or no galaxies. Cosmic voids are not merely regions of galaxy avoidance they also affect optical properties of the Universe. During the talk I will discuss how imagines of background objects are distorted when observed through cosmic voids. I will show how these distortions can help us to understand various phenomena and how we can use them to learn more about dynamics of cosmic voids and global properties of our Universe.
Tuesday Apr 30, 11:30
Giulia Savorgnan ()
Student Review: Giulia Savorgnan's 6-month review
Thursday Apr 18, 11:30
Anna Sippel (Swinburne)
Student Review: 30-month PhD Review
Abstract TBA
Tuesday Apr 16, 11:00
Andrew Johnson ()
Student Review: Andrew Johnson 6-month PhD review
Thursday Apr 11, 11:30
Mark Walker (Manly Astrophysics)
Colloquium: Solid hydrogen: interstellar dust
Abstract: Solid hydrogen is a volatile material. In its pure form it would sublimate rapidly under typical interstellar conditions, so it is widely believed to be absent from the diffuse ISM. But that idea is flawed: dust particles acquire surface charges, and for H2 these charges greatly attenuate the sublimation rate. It now appears possible for hydrogen grains to survive in the diffuse ISM, so their presence or absence has become an observational issue. Currently the most powerful diagnostics are associated with the trace molecular ion H6+, which is unique to the ionisation chemistry of condensed H2. The known vibrational transitions of these ions yield a striking match to the strong mid-IR bands of the ISM, suggesting that hydrogen grains are ubiquitous.
Thursday Apr 4, 11:30
Erika Nesvold (University of Maryland, Baltimore County)
Colloquium: A New Collisional Algorithm for Modeling Debris Disks
Abstract: Spatially resolved debris disk images from optical and infrared observatories show spectacular patterns and substructures (e.g. Fomalhaut's eccentric ring, beta Pictoris' inclined secondary disk). Undetected exoplanets could create many of these features via gravitational perturbations; many authors have analyzed resolved images of debris disks to predict the presence of exoplanets and constrain their physical properties. Most debris disk models, however, neglect the effects of the planets on the structure and collisional behavior of the population of larger parent bodies that produce the dust grains seen in the optical and infrared. I will give an overview of the current state of debris disk modeling and present the Superparticle Model/Algorithm for Collisions in Kuiper belts (SMACK), a new method for simultaneously modeling, in 3D, the collisional and dynamical evolution of parent bodies in a debris disk with planets. The size distributions and surface densities output by SMACK models can be used to generate simulated images of disks at various wavelengths. By comparing these simulated images with high-resolution observations, we can predict the presence of embedded planets and constrain their masses and orbital parameters.
Thursday Mar 28, 11:30
Elisa Boera ()
Student Review: Elisa Boera's 18-month review
Tuesday Mar 26, 11:30
Student Review: 18 Month Review - Genevieve Shattow
Thursday Mar 21, 11:30
Jakob Walcher ( AP Postdam)
Colloquium: Baryonic physics in galaxy evolution as seen by the CALIFA survey
Abstract: Ironically, while the predictions on the dark side of the cosmological "concordance" model LambdaCDM are well understood theoretically, many open questions in cosmology and galaxy evolution revolve around the difficult physics of the luminous, baryonic matter. The Calar Alto Legacy Integral Field Area Survey (CALIFA) is designed to study the baryonic physics of nearby galaxies by providing integral field spectroscopic data cubes in the optical wavelength domain of 600 galaxies of all morphological types. I will present the survey, show the current status, describe the science potential and advertise recent science results. Science results to be shown address 1) characterization of the local galaxy population in terms of kinematics, ionized gas and stellar populations, 2) galaxy transformation from star forming to quiescent, 3) mass build-up of stars over the history of the universe, 4) the origin of the mass-metallicity relationship, 5) chemical evolution of early type galaxies.
Thursday Mar 14, 11:30
Tyler Evans ()
Student Review: Tyler Evans' 30 month review
Tuesday Mar 12, 11:30
Rebecca Allen (Swinburne)
Student Review: Rebecca Allen's 6-month review
Thursday Mar 7, 11:30
Aaron Dotter (ANU)
Colloquium: Horizontal Branch Morphology in Globular Clusters
Abstract: The study of horizontal branch (HB) morphology in globular clusters has a long and distinguished history. Consider two examples: (1) Our current understanding of galaxy formation was strongly influenced by HB morphology in the Galactic globular cluster population. (2) The current renaissance in globular cluster studies inspired by the discovery of multiple stellar populations within them was predicted because of peculiarities in the HB morphology of some clusters. In my talk, I will review the development of our understanding of HB morphology relating to both of these important problems and discuss what is needed in order to make further progress.
Tuesday Feb 19, 11:45
Student Review: Emily Petroff
Thursday Feb 14, 11:30
Sarah Martell (AAO)
Colloquium: Multiple stellar populations in globular clusters: detailed observations, big consequences
Abstract: Our understanding of globular clusters has changed significantly in the past thirty years, from isolated, simple stellar populations to complex, self-enriching systems with a crucial role in galaxy formation. Developments in instrumentation have driven this change by allowing us to capture a more complete picture of chemical abundances in stars from the main sequence to the tip of the red giant branch. I will describe the current picture of globular cluster formation and self-enrichment, ongoing research on multiple stellar populations in globular clusters, and the questions we hope to address in the future
Thursday Jan 31, 11:30
Trevor Mendel (MPE)
Colloquium: The highs and lows of galaxy evolution
Abstract: Galaxies today are much less active than their counterparts 8 billion years ago. Since then, the cosmic star formation rate density has decreased by nearly a factor of 10, so that today over half of all galaxies are passive. Despite the wealth of observational data tracing the buildup of passive galaxies with cosmic time, our physical picture of galaxies' transition from star forming to passive remains incomplete, due in part to the short-lived nature of observational quenching signatures. In this talk I will discuss the selection of a large sample of rare local galaxies "caught in the act" of shutting down their star formation, made possible by the huge data volumes of the Sloan Digital Sky Survey. I will show that the presence of a stellar bulge seems to be a necessary part of the quenching process, and that stellar mass appears to be the best indicator of whether or not a galaxy will cease forming stars regardless of its surrounding environment.
Thursday Jan 24, 11:30
Paul Nulsen (CfA-Harvard)
Colloquium: Forming Sloshibng Cold Fronts from Cluster g-modes
Abstract: Gas "sloshing" due to minor mergers leads to the formation of the "cold fronts" seen in X-ray images of many galaxy clusters. The sloshing motions can be modelled as superpositions of dipolar g-modes. The broad spectrum of g-modes excited in a minor merger forms the spiral structure associated with sloshing because the Brunt-Vaisala frequency decreases with increasing radius. Cold fronts develop as a purely kinematic effect. With modest initial perturbations, they form in regions of converging flow, at locations where displaced fluid elements would otherwise need to pass through one another. The spiral pattern expands in an approximately self-similar manner, so that the cold fronts move out radially at nearly constant, low speeds. This can provide a means of estimating merger ages from systems of cold fronts.