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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
Applied Science Building, Room 406
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2005 Colloquia


December 15 @ 15:30
Chris Matzner (Toronto)
Title: Creation of small stars in the birth of massive clusters
Most stars are formed in clusters, and massive stars in particular are always found amid many smaller stars. The precursor to a cluster is a dense turbulent molecular region, likely the prerequisite for massive star formation. What does this environment imply for the creation of low-mass stars? I consider two aspects of this question. First, do models of high-mass star formation imply that low-mass stars form within the protostellar disks of massive stars? Second, what determines the typical stellar mass? The answers to both beg further questions.
December 5 @ 16:00
Tobias Westmeier (Bonn)
Title: High-velocity clouds around the Milky Way and the Andromeda Galaxy
High-velocity clouds (HVCs) are defined by their high radial velocities which are incompatible with a participation in the normal rotation of our Galaxy. They are observed mainly in the 21-cm line of neutral hydrogen. HVCs can be found all over the sky in the form of large complexes as well as compact, isolated clouds. To study their physical properties and their spatial distribution in more detail, we carried out single-dish and synthesis observations of several compact high-velocity clouds (CHVCs). Our observations show that many CHVCs appear to be distorted by the ram-pressure forces of an ambient medium, suggesting that they are located in the gaseous environment of the Milky Way where the particle densities are high enough to account for the observed interaction effects. To substantiate the concept of a circum-galactic population of HVCs we carried out an HI blind survey of a large area around the Andromeda Galaxy (M31). We found several HVCs near the disk of M31, but not a single HVC was found beyond a projected distance of about 50 kpc, confirming that HVCs are located in the vicinity of the large galaxies. The discovered HVCs have diameters of the order of 1 kpc and HI masses of typically a few times 10^5 solar masses. Follow-up synthesis observations with the WSRT show that some of the HVCs near M31 are probably associated with the recently discovered giant stellar stream. Another HVC near NGC 205 may also be of tidal origin, whereas other HVCs around M31 are isolated.
December 1 @ 11:30
Mary Putman (Michigan)
Title: How Gas Gets into Galaxies
Updated models for the formation of a spiral galaxy have the majority of the baryons remaining in a gaseous halo surrounding the galaxy. I will present a comparison between the condensed clouds in these models and our knowledge of the gaseous content of the Galactic halo and discuss how future surveys will probe both these clouds and the elusive diffuse hot halo. In addition, the gaseous halos of other spiral galaxies will be discussed in the context of nearby absorption line systems tracing extended galaxy halos.
November 25 @ 11:30
Stefan Keller (RSAA)
Title: SkyMapper and the Stromlo Southern Sky Survey
The SkyMapper telescope currently under construction by RSAA, ANU is the first of a new breed of wide-field survey telescopes. The 1.35m SkyMapper telescope will possess a 16kx16k pixel focal plane over a 5.7 square degree field of view. Using the instrument we plan to provide the first digital optical survey of the southern sky.
The Stromlo Southern Sky Survey will be analogous to the SDSS photometric survey in the north with improved blue sensitivity, a filter set tailored to discerning stellar parameters and temporal coverage. In this talk I will discuss the science prospects for SkyMapper including how you can get involved with this new Australian resource.
November 24 @ 11:30
Simon Ellis (AAO)
Title: The Evolution of Galaxies in High Redshift Clusters
I will present a study of the properties of galaxies in one of the most massive (10^15 Msun), high redshift (z=0.89) clusters known. Photometry has been measured in the V, R, I, z, F606W, F814W, J and K bands to a depth of K=20.5=K*+2.5 and spectroscopy confirms 27 K band selected galaxies as members of the cluster. The V-K colours are equivalent to a rest-frame colour of approx. 270nm-J, and provide a very sensitive measure of star-formation activity. Hubble Space Telescope imaging with the Advanced Camera for Surveys has been used to morphologically classify the galaxies.
Many galaxy properties are consistent with an old, passively evolving population. The K band luminosity function is consistent with purely passive evolution, and a redshift of formation z>1.5. The colour- magnitude relations of the early-type member galaxies form a clear red-sequence in all colours. The scatter and slope of the relations show no evolution compared to the equivalent Coma cluster relations, suggesting the stellar populations are already very old at z=0.89. The normalisation of the relations has been compared to models based on synthetic stellar populations, and are most consistent with stellar populations forming at z >3.
However, we also find evidence for evolution of galaxies in clusters. The cluster has a low early-type fraction compared to nearby clusters, with only 33 per cent of the confirmed cluster members having types E or S0. Some galaxies of late-type morphology were found to lie on the red-sequence of the colour-magnitude relation, suggesting that they have very similar stellar populations to the early-type galaxies, and may be in the process of transition.
October 25 @ 4.00
Michael Truss (St. Andrews)
Title: Accretion near the Eddington limit in black hole X-ray binaries
The galactic microquasar GRS1915+105 has been in a continuous state of outburst since its discovery in 1992. Its X-ray luminosity is highly variable, but spends at least half the time beyond the Eddington limit. I discuss how this system might be relevant to our understanding of ultra-luminous X-ray (ULX) sources observed in other galaxies and present SPH simulations of GRS1915+105 which shed some light on its extreme behaviour.
October 19 @ 11:30
Baerbel Koribalski (ATNF)
Title: The Local Volume HI Survey
October 6 @ 16:00
Helmut Jerjen (ANU)
Title: Harmonizing Lambda CDM with Observations: A Search for the Missing Dwarf Galaxies with SkyMapper and HST
September 22 @ 11:30
Indra Bains (UNSW)
Title: TBD
September 15 @ 11:30
Yeshe Fenner (Swinburne)
Title: TBD
August 25 @ 11:30
Renyue Cen (Princeton)
Title: TBD
August 19 @ 16:00
Chris Tinney (AAO)
Title: Proposal Writing for Fun and Profit... and a Career
August 19 @ 11:15
Martin Smith (Kapteyn)
Title: Milky Way Microlensing with OGLE
Gravitational microlensing is a unique tool for studying our own Galaxy. By highlighting a series of key results from the Polish-American OGLE collaboration, I will review some of the important findings that have been made. These results contribute towards our understanding of various phenomena, ranging from topics as diverse as the structure and dynamics of the Galaxy to the nature of extra-solar planets. In addition, I will mention some of the non-microlensing science that can be done with these datasets, such as constructing proper motion catalogues and extinction maps towards the Galactic bulge.
August 8 @ 11:30
Michael Kramer (University of Manchester)
Title: Testing General Relativity with the Double Pulsar
July 22 @ 11:30
Michael Brown (Princeton)
Title: The NOAO Deep Wide-Field Survey
The NOAO Deep Wide-Field Survey (NDWFS) is a multiwavelength survey designed to study the evolution of galaxies, AGNs, and large-scale structure since z=5. The survey consists of two 9 square degree fields imaged with Kitt Peak and CTIO telescopes. In addition, there is imaging and spectroscopy from Chandra, GALEX, Gemini, HST, Keck, the MMT, Spitzer, Westerbork, and the VLA. I will provide a brief overview of recent science results from our northern Bootes field, including z=2 obscured IR sources and AGN evolution. I will discuss in detail recent results on the evolution of galaxy clustering in the Bootes field. Our preliminary measurements show galaxy clustering at z=1 (in comoving coordinates) is remarkably similar to galaxy clustering at z=0.1. This is broadly consistent with the predictions of hierarchical models of galaxy and structure formation. As galaxy clustering does not rapidly evolve, it will become an important tool for tracing galaxy evolution from z=5 to z=0.
July 21 @ 11:30
Doug Johnstone (NRC/HIA, Victoria)
Title: A taste of the SCUBA2 future
The problem of star formation is not FORMING stars, but rather NOT forming stars. Indeed, gravitational collapse would proceed quickly in most molecular clouds if not for the addition of non-thermal support mechanisms such as turbulent motions and magnetic fields. Only recently have observations of molecular clouds become sufficient to rigorously test the various theoretical models for cloud support. In this talk I will discuss an ongoing survey, the COMPLETE Survey of Molecular Clouds (cfa-www.harvard.edu/COMPLETE/), and the recent discovery of an extinction threshold for structure formation. I will end the talk with a look at the future of molecular cloud observations in the era of SCUBA2 and HARP at the JCMT, and the arrival of ALMA. Will Star Formation studies become much more similar to Cosmological studies?
July 18 @ 11:30
Stuart Gill (Swinburne)
Talk Cancelled
July 14 @ 11:30
Peter Thomas (Sussex)
Title: Simulations of Galaxy Clusters
I will discuss the generation of large mock catalogues of galaxy clusters using hydrodynamical simulations. Individual clusters show a wide variety of formation histories but the population of clusters follow well-defined scaling relations whose evolution is a powerful test of the physical model for entropy generation in the intracluster medium.
June 28 @ 11:30
Peder Norberg (ETH)
Title: Large Scale Structure from the 2dF Galaxy Redshift Survey
The 2dF Galaxy Redshift Survey (2dFGRS), together with the SDSS galaxy redshift survey, provide an unprecedented amount of information that can be used to constrain models of galaxy formation. In this talk, I will in particular focus on clustering results from the 2dFGRS and how they can constrain our current structure formation paradigm. The strength of the datasets like 2dFGRS and SDSS reside in their abundance, allowing for the first time the creation of statistically large and homogeneous galaxy samples: samples can be split by colour and luminosity simultaneously. In configuration space, results for 2-point and 3-point statistics are presented, together with recent measurements of the linear and non-linear bias parameters. In Fourier space, the precise determination of the final 2dFGRS power spectrum allow us to set, together with recent CMB data, new tight constraints on various cosmological parameters.
June 23 @ 11:30
Kate Brooks (ATNF)
Title: New Views on the Carina Nebula
The Carina Nebula, at a distance of 2.2 kpc, is one the most extreme and complex cases of massive stars interacting with their environment. It is part of a southern giant molecular cloud complex that extends over 130 pc. The two most influential star clusters in the nebula are Trumpler 14 and Trumpler 16 which contain a combined total of 34 O-type stars, including 6 very rare and massive 03 stars. Trumpler 16 also contains one of the most massive stars known -- Eta Carinae. Such a high concentration of massive stars remains unique in our Galaxy. A very dynamic picture is now emerging for the Carina Nebula which includes numerous sites of ongoing star formation, giant dust pillars that point towards Eta Carinae, wide-spread photodissociation regions and large wind-blown cavities. Evidence for giant bow shocks and proplyds also exist. In this talk I will review these new findings and argue that there remains a wealth of information to be gained from future studies of this region.
June 16 @ 16:00
Duncan Forbes (Swinburne)
Title: Globular Clusters in the Local Group
I will review the status of our knowledge about the ~700 globular clusters known in the Local Group. Starting with our own Galaxy and its satellites, I will then discuss highlights from other galaxies. Globular clusters will be used to infer the star formation and accretion history of their host galaxies.
June 2 @ 16:00
David Radburn-Smith (Durham)
Title: Peculiar Motions: Probes of the Local Mass Distribution
Peculiar motions are a powerful tool for probing the underlying matter distribution of the local Universe. By calibrating the PSCz velocity field with type Ia supernovae, the redshift distortion parameter beta (=Omega^0.6/b) can be calculated and 3D velocity and density maps of the local Universe can be constructed. Peculiar motions have also been used to analyse the Great Attractor (GA). This massive overdensity, which is likely to be responsible for the bulk of our own motion, is obscured by the plane of the Milky Way; hence, its precise structure is still largely unknown. However, with many recent redshift measurements and multi-wavelength observations in the region, the underlying 3D composition of the GA is now being revealed.
May 26 @ 16:00
Simon Driver (ANU)
Title: The Millenium Galaxy Catalogue
With cosmology solved its time to address the problem of how the baryons got from such a smooth distribution to such a lumpy one today. To start this investigation we need to better define where and in what state the baryons are in today. This requires a detailed local census of galaxies. Our survey, the MGC, is essentially a deeper higher resolution extension of a 37 sq degree region of the 2dFGRS. The dataset is being used to define the nearby galaxy population and its generic properties in advance of JWST. In this talk I'll describe the database and some key results on the nearby galaxy luminosity function and go on to explain why I think we need to move beyond global measures of galaxies (colour, star-formation rate etc) and start to measure the properties of the key components and constituents.
May 12 @ 16:00
Anna Frebel (RSAA)
Title: HE 1327-2326: The most metal-poor star known with [Fe/H]=-5.4
In a sample of ~1800 metal-poor candidates selected from the Hamburg/ESO survey, we recently discovered HE 1327-2326, a subgiant or dwarf with [Fe/H] = -5.4. It is only the second star with such an extremly low metallicity of [Fe/H] < -5.0. I will present our abundance analysis of this very peculiar object (very high C and N, non-detection of Li and high Sr abundances) together with models which try to explain the observed abundance pattern. The discovery paper was recently published in 'Nature'.
May 9 @ 16:00
Alice Quillen
Title: Sculpting circumstellar disks and galactic disks
Through their gravitational force, planets sculpt the gas and dust in their vicinity. While extra solar planets themselves can be difficult to detect, their long term effect on observable nearby material can be exploited to infer the presence and properties of nearby planets. I will introduce scenarios and techniques developed to search for planets from their effect on planetary disks. These methods probe and are dependent on the properties of the disks and are effective in the outer parts of extrasolar systems, a region where most other planet detection techniques fail. In the next decade we expect that radial velocity surveys will increase our knowledge of the Milky Way's shape, dynamics and evolution. The velocity distribution in the Solar neighborhood contains a wealth of structure, much of which remains unexplained. I will introduce how resonances with bars and spiral arm structures can influence the distribution of stars in both physical and velocity space.
May 3 @ 16:00
George Hobbs (ATNF)
Talk Cancelled
April 21 @ 11:00
Cristina Popescu (MPIK Heidelberg)
Title: Viewing the Dusty Universe
Understanding dust emission is crucial to the understanding of the physical processes in galaxies and of the star-formation history of the Universe as a whole. The obvious starting point to gain such an understanding is to look at emission from grains in star-forming galaxies in the Local Universe, also with respect to stellar emission, and to model the spectral energy distributions of these galaxies from the ultraviolet to the far-infrared/submillimeter. In this talk I will present recent progress in the characterisation of dust emission from spiral and dwarf galaxies based on observations made with cryogenic-cooled orbiting telescopes, and I will describe theoretical developments in the interpretation of multi-wavelength observations in terms of the intrinsic physical properties of these systems.
April 7 @ 16:00
D.J. Pisano (Naval Research Lab)
Title: What do loose groups tell us about galaxy formation?
I present the results of a Parkes Multibeam HI survey of six loose groups of galaxies analogous to the Local Group. This survey was sensitive to HI-rich objects in these groups to below 10^7 M(sun) of HI, and was designed to search for low mass, gas-rich satellite galaxies and potential analogs to the high-velocity clouds seen around the Milky Way. This survey detected a total of 79 HI-rich objects associated with the six groups, half of which were new detections. While the survey identified a small number of dwarf galaxies, no star-free HI clouds were discovered. The HI mass function and the mass function of the luminous halos for the six groups are consistent with those for the Local Group. This implies that these groups are true analogs to the Local Group and that the Local Group is not unique in its lack of low-mass dwarf galaxies as compared to the predictions of cold dark matter models of galaxy formation. This survey also constrains the distance to and HI masses of the compact high-velocity clouds (CHVCs) around the Milky Way. The lack of CHVC analog detections implies that they are distributed within <160 kpc of the Milky Way and have average HI masses of <4x10^5 M(sun). The spatial distribution of CHVCs is consistent with the predictions of simulations for dark matter halos. Furthermore the CVDF of Local Group galaxies plus CHVCs matches the predicted CVDF of cold dark matter simulations of galaxy formation. This provides circumstantial evidence that CHVCs may be associated with low-mass dark matter halos.
March 24 @ 16:00
Rob Sharp (AAO)
Title: Sequence structure in the Red Rectangle
The identification of the carriers of the Diffuse Interstellar Bands represents one of the longest outstanding problems in astronomical spectroscopy. While the final identification of the molecules responsible for the absorption will rely on laboratory observation, the complexities of such observations have hindered progress in the past. I review the role that astronomical observations must play in constraining the parameter space which is to be search, giving recent VLT observations of the Red Rectangle nebula as an example of the pivotal role that targeted observations must play in this inter-disciplinary subject. I present an interperate of the observations of the 5800A Red Rectangle band as a type of molecular emission familiour to chemists but previously overlooked in the astronomical literature.
March 22 @ 16:00
Amanda Karakas (Saint Mary's University)
Title: Nucleosynthesis in Asymptotic Giant Branch Stars
Low and intermediate mass stars pass through the Asymptotic Giant Branch (AGB) phase of stellar evolution. It is on the AGB that the richest nucleosynthesis occurs, driven by thermal instabilities of the helium-burning shell and envelope burning in the most massive stars. In this talk I will give an introduction to the structure and evolution of AGB stars, followed by a discussion of the various nucleosynthesis and mixing processes that alter the surface composition of the star. I will discuss a couple of applications including the globular cluster abundance anomalies, the so-called super-AGB stars and the production of the neutron-rich magnesium isotopes. I will finish with a discussion of some of the uncertainties that effect the stellar yields.
March 18 @ 16:00
Daisuke Kawata (Swinburne)
Title: GCD+: Galactic Chemodynamics Code
We introduce a new galactic chemo-dynamical evolution code, called GCD+ (Kawata & Gibson 2003), for studies of galaxy formation and evolution. This code is a vector/parallel three-dimensional tree N-body/smoothed particle hydrodynamics code which includes self-gravity, hydrodynamics, radiative cooling, star formation, supernova feedback, and metal enrichment. GCD+ includes both SNe II and SNe Ia, and chemical enrichment from intermediate mass stars, taking into account the lifetime of progenitor stars. We present our recent studies of galactic chemodynamics with GCD+, especially about elliptical galaxy formation, and dwarf speroidal galaxy formation.
March 9 @ 16:00
Jim Liebert (Steward)
Title: White Dwarfs from the SDSS as Tracers of the Ages amd Evolution of Populations in the Galaxy
Among its numerous products, the Sloan Digital Sky Survey has tripled the number of spectroscopically-identified white dwarfs, found many unusual examples, and contributed order of magnitude increases in the samples suitable for determining the ages and star formation histories of the Galactic disk and halo. I present initial results from the analysis of these samples.
March 7 @ 16:00
Paul Francis (ANU)
Title: What's new with Gemini
March 3 @ 16:00
Seth Redfield (Texas)
Title: Our Interstellar Environment: Developing a Survey of the Local Interstellar Medium
High spectral resolution observations are critical to understanding the morphological structure of nearby interstellar material. The local interstellar medium (LISM), extending about 100-200pc to the edge of the Local Bubble, is a unique environment in which to study a diverse set of ISM phenomena in three-dimensional detail, including the interaction of the Sun with its interstellar surroundings. I will discuss efforts to combine high resolution UV and optical observations of nearby stars into a comprehensive morphological model of the LISM.
March 2 @ 16:00
*** AGSE 203 ***
Eiichiro Kokubo (NAOJ)
Title: Oligarchic Growth of Protoplanets and Diversity of Planetary Systems
We investigate the formation of protoplanet systems from planetesimal disks by global N-body simulations of planetary accretion. For application to extrasolar planetary systems, we study the wide variety of planetesimal disks. The results are all consistent with the prediction from the ``oligarchic growth'' model. We derive how the growth time scale, the isolation (final) mass, and the orbital separation of protoplanets depend on the initial disk mass and the initial disk profile. Based on the oligarchic growth model and the conventional jovian planet formation scenario, we discuss the diversity of planetary systems.
Feb 24 @ 16:00
Takashi Okamoto (Durham)
Title: Disc galaxy formation in a LCDM universe
We have performed hydrodynamic simulations of galaxy formation in a LCDM universe. We study galaxy formation in a halo that has a quiet merger history. Our model employs two distinct star formation modes, namely quiescent and burst modes, together with a multi-phase description for the interstellar medium. We assume that the star formation efficiency is much higher in the burst mode than in the quiescent mode, and allow stars born in the burst mode to have a top-heavy IMF. By changing the model for the burst, we show that the galaxy morphology is very sensitive to the modelling of the star formation and feedback. We find that a reasonable disc galaxy forms if we suppose that bursts are triggered by strong shocks. Since the galaxy has a richer merger history at earlier epochs in a hierarchical structure formation universe, more stars form in the burst mode, so the stronger feedback due to the top-heavy IMF significantly suppresses the early collapse of the baryons.