For more information on colloquia at the Centre for Astrophysics and Supercomputing please contact Dr. Felipe Marin ()
Swinburne Virtual Reality Theatre
AR Building, Room 104
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Thursday Sep 5, 11:30
Jesus Falcon Barroso (Instituto de Astrofisica de Canarias)
Thursday Aug 8, 11:30
Gabor Worseck (MPIA)
Thursday Jul 25, 11:30
Leon Koopmans (Kapteyn Institute)
Thursday Jul 4, 11:30
Rob Crain (Leiden (Netherlands))
Tuesday Jul 2, 11:30
Molly Peeples (UCLA)
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.
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.
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 ()
Giulia Savorgnan's 6-month review
Thursday Apr 18, 11:30
Anna Sippel (Swinburne)
30-month PhD Review
Tuesday Apr 16, 11:00
Andrew Johnson ()
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 ()
Elisa Boera's 18-month review
Tuesday Mar 26, 11:30
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 ()
Tyler Evans' 30 month review
Tuesday Mar 12, 11:30
Rebecca Allen (Swinburne)
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
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.