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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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2008 Colloquia


Dec 18th @ 11:30am
Chris Blake (Swinburne)
Title: The WiggleZ Dark Energy survey -- half-term report The WiggleZ survey at the Anglo-Australian Telescope is now 50% complete. I'll review the survey progress and show some initial results on the clustering of galaxies and cosmological parameters.
Dec 10th @ 11:30am
Roberto Abraham (University of Toronto)
Title: Looking for redshift 10 galaxies before JWST
I will describe the plans for the Gemini Genesis Survey, a next-generation survey intended to search for the first galaxies which formed in the Universe. This survey will be conducted using the FLAMINGOS-2 Tandem Tunable Filter (F2T2), which is an engineering prototype for the James Webb Space Telescope's Tunable Filter Imager. F2T2 is designed to operate in concert with Gemini's upcoming Multi-Conjugate Adaptive Optics (MCAO) system, so in this talk I will also describe why this particular form of adaptive optics is likely to prove transformative. The combination of F2T2 and MCAO will be fairly powerful, and there's a finite chance that Gemini will soon be finding galaxies at z>10.
Dec 9th @ 11:30am
Joris Verbiest (Swinburne)
Title: Long-term Millisecond Pulsar Timing and Gravitational Wave Detection

The high stability of some millisecond pulsars (MSPs), along with ever increasing levels of timing precision, has been predicted to enable detection of gravitational wave (GW) effects on the Earth. Specifically, it has been shown that GWs arising from hierarchical galaxy formation - and associated supermassive black hole binaries - would be detected provided 20 MSPs can be timed for five years or more at a precision of ~100 ns. The practical feasibility of this scenario is investigated.

We present results from a long-term timing campaign at the Parkes radio observatory, for the first time providing insights into the timing stability of a large number of MSPs (20). On one of our sources we obtain 200 ns timing precision, which is a first over timescales of a decade or more. More than half of our sample displays stability at current levels of timing precision and a simple analysis on some of our brightest sources demonstrates the potential for sub-100 ns timing.

Using these results, we evaluate the potential for timing array efforts on the major radio telescopes of the world and are cautiously optimistic about the potential for a GW detection within the coming decade.

Dec 4th @ 11:30am
George Hobbs (ANTF)
Title: A unified description for time variability in pulsars

Based on a new study of pulsar spin-down irregularities and previous observations of an unusual, intermittent pulsar, PSR B1931+24, I present a model for pulsar timing noise. Our model links many pulsar phenomena including moding, nulling, intermittency, pulse shape variability and timing noise. Our model shows that the timing residuals for PSR B1828-11 and its pulse shape variations can be explained, suggesting that this pulsar is not undergoing free precession as previously thought. The ability to model and, hence, remove the timing irregularities leads to the possibility of forming a perfectly stable pulsar clock that could be used to improve tests of general relativity, to search for the elusive gravitational waves and to produce a pulsar-based timescale that, over long time scales, will be competitive with existing terrestrial time scales. In my talk I will describe observations of pulsars over many decades, explain the new model and discuss its implications

Nov 28th @ 2 - 4pm
Tim De Zeeuw (Director, ESO)
Title: Presentation on ESO with Q&A Session
Nov 27th @ 11.30am
Philipp Podsiadlowski (Oxford University)
Title: The Origin of the UV upturn in Elliptical Galaxies
The excess of far-ultraviolet (far-UV) radiation in elliptical galaxies has remained one of their most enduring puzzles. In contrast, the origin of old blue stars in the Milky Way, hot subdwarfs, is now reasonably well understood: they are hot stars that have lost their hydrogen envelopes by various binary interactions.In this talk I first review the history and models for the UV exces and then discuss the main evolutionary channels that produce hot subdwarfs, presenting the results of binary population synthesis simulations that reproduce the main properties of the Galactic hot-subdwarf population. Applying the same model to elliptical galaxies, I show how this model can explain the main observational properties of the far-UV excess, including the far-UV spectrum, without the need to invoke ad hoc physical processes. The model suggests that the UV excess is not a sign of age, as has been postulated previously, and predicts that it should not be strongly dependent on the metallicity of the population.
Nov 21st @ 11:30am
Taft Armandroff (Director, W. M. Keck Observatory)
Taft Armandroff has served as Director of the W.M. Keck Observatory since July 1, 2006. His talk will include recent progress at Keck Observatory on new instruments, telescope and instrument upgrades, and plans for the future. A number of instrumental initiatives are underway, including a detector upgrade for the red arm of LRIS, the new multi-object infrared spectrograph MOSFIRE, and the MAGIQ guider enhancement / replacement project. Adaptive optics enhancements that will be discussed include enabling laser-guide-star adaptive optics on the Keck I telescope, in addition to the existing system on Keck II, and the design of a next-generation adaptive optics system and related instrumentation. Statistics on the scientific output and impact of Keck Observatory will also be featured.
Nov 20th @ 18:00
Professor Taft Armandroff (Director, W. M. Keck Observatory)
Public Lecture: The Astronomical Frontier: New Opportunities for Discovery at the W. M. Keck Observatory

The twin Keck 10-metre telescopes on the summit of Mauna Kea in Hawaii have been the largest optical telescopes in the world for more than the last decade. They have been at the forefront of astronomical discovery, through their unrivaled observations of planets around other stars to galaxies seen billions of years back in time.

In this talk, Dr Taft Armandroff, the Director of the Keck Observatory, will look to these powerful telescopes' future, describing the exciting new discoveries they are poised to make in the next decade and beyond.

Location AGSE 207 (AGSE Building Cnr Wakefield and William Streets, Hawthorn). For further information or to reserve a seat: email contact@astro.swin.edu.au or contact Carolyn Cliff on 9214 5569.

Nov 13th @ 11:30am
Krzysztof Bolejko (Melbourne University)
Title: Large scale inhomogeneities acting like dark energy
Accelerated expansion, modeled by a positive cosmological constant, is an essential element of the current standard cosmological model of the Universe. This accelerated expansion is driven by dark energy. However, dark energy has never been observed directly and since it has very unusual properties some began to ask whether dark energy is real or if it is the description of the Universe which requires the existence of such an exotic entity that is invalid. In my talk I will discuss if inhomogeneities observed in the Universe can account for dark energy.
Nov 6th @ 11:30am
Ned Taylor (Leiden University)
Title: The 10^11 M_sol Question: massive galaxy formation and the rise of the red sequence
Efforts to reproduce the joint color-magnitude distribution of z < 1 galaxies have forced the introduction of some 'quenching' mechanism that operates to prevent star formation in massive galaxies. In this talk, I will present the color-magnitude and color-mass diagrams for z < 2, based on a new, near infrared-selected catalogue of the Extended Chandra Deep Field South. I will use these data to explore the existence of the red sequence at z > 1, the color evolution of the red galaxy population, and the relative number of blue/red (as a proxy for active/passive) galaxies within the general population of massive, field galaxies. The data suggest a 'long migration' of massive galaxies onto the red sequence: at most, 1/5 massive galaxies in the local universe were already on the red sequence at z ~ 2, while roughly 1/2 (re)joined the red sequence only after z ~ 1. These results provide new constraints for models of galaxy formation, and particularly on the process whereby galaxies are quenched.
Oct 30th @ 11:30am
Adam Deller (Swinburne)
Title: VLBI pulsar astrometry with the Long Baseline Array
In this talk, I will describe the motivation for astrometric observations of pulsars, briefly cover the observational technique, and then describe the results I have obtained on eight southern hemisphere pulsars during my thesis. After summarising the observational results for the survey, I will focus of two on the highlights - the most precise determination of a pulsar distance to date (PSR J0437-4715) and the consequent improved tests of general relativity, and the first distance determination of the famous 0737-3039A/B double pulsar system, which has dramatic implications for estimates of double neutron star merger rates.
Oct 23rd @ 11:30am
Paul Lasky (Swinburne)
Title: Neutron stars in Bekenstein's modified theory of gravity: Independent tests of gravity
Modified theories of gravity have had recent success in explaining various phenomena without the need for dark matter or dark energy. Bekenstein's Tensor-Vector-Scalar (TeVeS) theory, which is a relativistic generalization of Milgrom's Modified Newtonian Dynamics (MoND), has been able to explain strong gravitational lensing phenomena, galaxy rotation curves and the Tully-Fisher relation, as well as cosmological scenarios such as reproducing key features of the CMB power spectra and large scale structure. However, it is difficult to observationally discern the differences between TeVeS and predictions made within a Lambda-CDM concordance model. This implies that alternative tests are required that independently verify which thoery is correct. For this we turn to the strong-field regime of TeVeS, in particular studying both black holes and neutron stars. In this talk, I provide an overview of the successes of both MoND and TeVeS. I then provide a brief overview of the theory of TeVeS, including showing the major differences between it, General Relativity and also scalar-tensor theories of gravity. I then discuss in some detail the derivation of neutron stars in TeVeS. I am able to provide independent constraints on the free parameters in the TeVeS theory using current observations of the masses of neutron stars. Moreover, I discuss the possibility of further constraining these parameters using future observations in the electromagnetic spectrum, as well as with gravitational wave astronomy.
Oct 21st @ 11:30am
Andrew Walsh (James Cook University)
Title: HOPS, disks and JCU Astronomy
I will give a short introduction to the JCU internet astronomy program, as well as an overview of the research conducted and the challenges faced in this program. I will also talk about two of my main research topics: HOPS (the H2O southern galactic Plane Survey) is a survey at 12mm using the Mopra radiotelescope. We aim to cover 90 square degrees of the southern Galactic plane over three years. We will observe multiple spectral lines, including water masers, ammonia and cyanoacetylene. I will report on the first years observations where we have covered 31 square degrees of the Galactic plane. Many searches have been made for accretion disks around young high mass stars, but to date these searches have been largely unsuccessful. I will discuss a new method we have been using to identify high mass disks by observing highly excited transitions of ammonia and will present some of our recent results from the ATCA.
Oct 16th @ 11:30am
Charley Lineweaver (MSSSO, ANU)
Title: A comprehensive comparison of the Sun to other stars: searching for self-selection effects
If the origin of life and the evolution of observers on a planet is favoured by atypical properties of a planet’s host star, we would expect our Sun to be atypical with respect to such properties. The Sun has been described by previous studies as both typical and atypical. In an effort to reduce this ambiguity and quantify how typical the Sun is, we identify eleven maximally-independent properties that have plausible correlations with habitability, and that have been observed by, or can be derived from, sufficiently large, currently available and representative stellar surveys. By comparing solar values for the eleven properties, to the resultant stellar distributions, we make the most comprehensive comparison of the Sun to other stars. The two most atypical properties of the Sun are its mass and orbit. The Sun is more massive than 95 ± 2% of nearby stars and its orbit around the Galaxy is less eccentric than 93± 1% of FGK stars within 40 parsecs. Despite these apparently atypical properties, a chi2-analysis of the Sun’s values for eleven properties, taken together, yields a solar chi2 = 8.39±0.96. If a star is chosen at random, the probability that it will have a lower value (~ be more typical) than the Sun, with respect to the eleven properties analysed here, is only 29±11%. These values quantify, and are consistent with, the idea that the Sun is a typical star. If we have sampled all reasonable properties associated with habitability, our result suggests that there are no special requirements for a star to host a planet with life.
Oct 15th @ 18:30
Professor Bill Harris (McMaster University, Canada)
Public Lecture: Creative Reactions to the End of the World: From Galileo to the 21st Century Universe
The universe beyond the Earth has been an increasingly more astonishing place ever since Galileo's first discoveries with the telescope 400 years ago. Now, we are trying to understand a flood of revolutionary concepts such as hundreds of planets discovered around nearby stars and the chance of finding life elsewhere; dark matter around galaxies everywhere; vast amounts of shadowy "dark energy" throughout all of space; or giant black holes at the centers of galaxies. How did we get here? What does it mean? People as far back as Galileo's time have faced exactly the same questions about the outside world that we do now, and their reactions are as fascinating as the discoveries themselves.

The lecture is free, but as seating limited, please contact Carolyn Cliff 03 9214 5569 or ccliff@swin.edu.au to reserve a seat. Location: AR104

Oct 9th @ 11:30am
Federic Courbin (Observatoire de Sauverny, Switzerland)
Title: The energy profile of a quasar accretion disk in the Einstein Cross from chromatic microlensing : 3 years of VLT spectrophotometry
I will present the results of an ESO large program aimed at mapping the energy profile of the accretion disk in the gravitationally lensed z=1.7 quasar known as the "Einstein cross". A new observational strategy is presented, using VLT Multi-Object-Spectroscopy of the Einstein Cross at 40 epochs spanning 3 years. The spectra are spatially deblended and accurately flux calibrated in order to follow the chromatic variations of the continuum due to microlensing by stars in the foreground spiral galaxy at z=0.05. A bayesian analysis of the resulting multi-band light curves support the theoretical energy profile predicted by Shakura and Sunyaev already in the 70s but never directly investigated observationally.
Oct 2nd @ 11:30am
Bill Harris (McMaster University)
Title: Mass/luminosity correlations for globular clusters and connections to events in galaxy formation
Sept 30th @ 11am
David Barnes & Chris Fluke Swinburne
Title: (Almost) Everything you wanted to know about using S2PLOT to visualise astronomy datasets
S2PLOT is an advanced three-dimensional plotting library with support for standard and enhanced display devices. Developed at the Centre for Astrophysics & Supercomputing, S2PLOT is steadily making its way into the astronomy community. With a PGPLOT-inspired interface, S2PLOT provides astronomers with elegant techniques for displaying and exploring 3-d data sets directly from their program code. We will demonstrate how to get started with S2PLOT and show off the wide range of functionality, including special features available in the forthcoming (open source) relase of version 2.4. Questions on how S2PLOT can help with your own research projects are strongly encouraged.
Sept 24th @ 11:30am
Bob Carswell (IoA, Cambridge)
Title: Temperatures in the interstellar media in high redshift galaxies
The heating/cooling balance in a gas effectively determines its temperature. Observationally temperatures have normally been determined by measuring excitation of atomic or molecular energy levels, though radiative mechanisms are often important and these affect the results. In some cases, however, it is possible to infer temperatures more directly by measuring the Doppler widths of spectral lines. The results from these methods using measurements of different atoms and molecules in quasar absorption spectra are compared, and some significant differences are found. In particular, the neutral hydrogen 21cm spin temperature favoured by some may not give the true temperature for any constituent. We confirm that neutral carbon excitation is dominated by radiative effects, and a choice of the lower molecular hydrogen excitation levels probably gives reliable kinetic temperatures in cool (a few 100K) regions. The prospects for investigating the high redshift analogues of the warm (10000K) regions found in the Galaxy are less encouraging.
Sep 17th @ 6:30pm
Professor Bob Carswell (IoA, Cambridge)
Public Lecture: Gravity and Light - Gravitational Lenses and Black Holes

The lecture is free, but as seating limited, please contact Carolyn Cliff 03 9214 5569 or ccliff@swin.edu.au to reserve a seat. Location: AR104

We explore how light behaves near massive objects, and show that for gravitational lenses, gravitational redshifts and black holes, the main concepts can be understood in general terms from Einstein's oft-quoted equation, E=mc^2.

Light paths are changed as they pass close to the sun and to massive galaxies, so giving us the idea of gravitational lenses which can change the appearance of distant galaxies and quasars. Some examples of multiply imaged quasars and lensed galaxies are given.

Gravitational redshifts of light from compact stars have been measured. In the extreme case of very compact objects - black holes - no light can escape at all. There are compelling reasons for believing that massive black holes reside near the centers of many galaxies, and particularly the center of the Milky Way.

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September 11th @ 3pm
Melanie Johnston-Hollitt (University of Tasmania)
Title: Radio observations as a tool for understanding cluster dynamics
Understanding the nature and evolution of galaxy clusters places important constraints on cosmological models. Currently, radio observations do not feature heavily among the diagnostic tools used to investigate galaxy clusters. However, recent results suggest that deep radio observations could provide important constraints on the precise dynamical state of galaxy clusters. Increasingly there is evidence to suggest that radio phenomena such as relics, halos, head-tailed galaxies and excessed of low-powered radio galaxies probe the dynamical history of clusters by tracing different phases and conditions. I will present an overview of the new results my students and I have obtained on using radio emission to probe the cluster environment including evidence to suggest that head-tailed galaxies trace the mass density of clusters and that radio luminosity functions suggest late stage mergers act to suppress the AGN population in clusters while at the same time triggering tidally induced starformation along preferred axes.
September 4th @ 3pm
Robert Williams (Space Telescope Science Institute)
Title: Resolving Emission-Line Abundance Discrepancies & A New Paradigm for the Nova Outburst?
(1) Observed intensities of forbidden and recombination lines in many nebulae differ from their predicted values by more than an order of magnitude, which has caused emission-line abundances to be called into serious question. We have used HST/STIS to independently derive nebular ion column densities from UV spectra of PNe central stars. We find good agreement with emission measures derived from the nebular forbidden lines, validating the use of forbidden lines in abundance determinations. (2) A high-resolution spectroscopic survey of novae has revealed short-lived heavy element absorption systems near maximum light, consisting of enriched Fe-peak and s-process elements. The absorbing gas is circumbinary and it pre-exists the outburst. Its origin appears to be mass ejection from the secondary star, presumably the result of large episodic mass transfer events from the secondary that initiate the nova outburst. The spectra of SNe Ia should be searched for such systems as they would confirm mass transfer binaries as SNe Ia progenitors.
September 4th @ 11:30am
Gary Da Costa (MSO)
Title: Does omega Centauri have tidal tails?
The results of a spectroscopic search with the AAT's 2dF multi-fibre spectrograph for candidate members of the unusual globular cluster Omega Centauri at and beyond the cluster tidal radius will be presented. Both radial velocity and line strength information is used to identify possible candidate members. The outcome is a limit on the fraction of the total cluster mass contained in the region between 1 and 2 cluster tidal radii, and will be discussed in the context of theories which postulate that Omega Centauri is the remnant nucleus of a tidally disrupted dwarf galaxy
September 3rd @ 11:00am
Max Spolaor (Swinburne)
Title: Galactic Archaeology: observational clues for galaxy formation mechanisms of early-type galaxies
August 21st @ 3pm
Anneke Praagman (Swinburne)
Title: TBD
August 14th @ 11:30am
Karl Glazebrook (Swinburne)
Title: Red Nuggets at high-redshift. The diminutive early history of Elliptical Galaxies
Recent observations from several near-IR selected samples, such as ours from the Gemini Deep Deep Surve,y have found substantial evidence for considerable size evolution in the population of massive elliptical galaxies at z>1.4. I will talk about the discovery of this phenomenon and the real challenge it presents for our models of galaxy evolution, with special attention to the 'red nuggets', massive r<1 kpc elliptical galaxies seen at this epoch, but which have completely disappeared today.
July 31st @ 11:30am
Brandon Kelly (University of Arizona)
Title: Observational Constraints on Quasar Structure
A succesful model for the nature of the quasar accretion process involves the UV/optical continuum arising from a geometrically thin, optically thick cold accretion disk, and the X-ray continuum arising from a hot, optically thin corona that Compton upscatters the disk UV photons. While it appears that the basic ingredients of the quasar engine are currently understood, a number of uncertainties remain, including the source of the viscosity that drives the accretion process, and the nature of the X-ray emitting region. Recently, it has become possible to investigate the dependence of quasar emission on black hole mass, enabling new opportunities for observationally constraining quasar structure. In this talk I will review techniques for estimating black hole mass in unobscured quasars. I will then discuss our recent work on studying how quasar optical/UV and X-ray emission depends on black hole mass and Eddington ratio, as well as how the variability properties of quasars depend on these quantities. I will discuss our results within the context of quasar structure and black hole feedback.
July 30th @ 18:00
Michael Kramer (Jodrell Bank Centre for Astrophysics)
Title: Public Lecture: Fundamental physics in Space: Was Einstein right?
Nature has provided us with superb cosmic clocks that are observable as pulsating radio sources - pulsars. Discovered in Cambridge more than 40 years ago, about 1800 are known by now, most of them discovered with the Parkes telescope in NSW. Pulsars are useful tools in studying fundamental physics, ranging from the properties of super-dense matter to tests of Einstein's theory of gravity, and from physics under extreme conditions to cosmology. This talk will summarize the most fascinating applications of pulsars and will also cast a look into the future where gigantic telescopes will revolutionize our observations of pulsars and potentially our understanding of physics.

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The lecture is free, but as seating limited, please contact Carolyn Cliff 03 9214 5569 or ccliff@swin.edu.au to reserve a seat.

July 23rd @ 11:30am
Robert Braun (ATNF)
Title: Opaque Atomic Gas and Star Formation Density in M31
We have undertaken a deep, wide-field HI imaging survey of M31, reaching a maximum resolution of about 50 pc and 2 km/s across a 95x48 kpc region. The HI mass and brightness sensitivity at 100 pc resolution for a 25 km/s wide spectral feature is 1500 M_Sun and 0.28 K. Our study reveals ubiquitous HI self-opacity features, discernible in the first instance as filamentary local minima in images of the peak HI brightness temperature. Local minima are organized into complexes of more than kpc length and are particularly associated with the leading edge of spiral arm features. Just as in the Galaxy, there is only patchy correspondence of self-opaque features with CO(1-0) emission. We have produced images of the best-fit physical parameters; kinetic temperature, opacity-corrected column density and non-thermal velocity dispersion, for the brightest spectral feature along each line-of-sight in the M31 disk. Spectroscopically opaque atomic gas is organized into filamentary complexes and isolated clouds down to 100 pc. Localized opacity corrections to the column density exceed an order of magnitude in many cases and add globally to a 30% increase in the atomic gas mass over that inferred from the integrated brightness under the usual assumption of negligible self-opacity. Opaque atomic gas first increases from 20 to 45 K in kinetic temperature with radius to 12 kpc but then declines again to 20 K beyond 20 kpc. We have extended the resolved star formation law down to physical scales more than an order of magnitude smaller in area and mass than has been possible previously. The relation between total-gas-mass- and star-formation-rate-density is significantly tighter than that with molecular-mass and is fully consistent in both slope and normalization with the relation found in the molecule-dominated disk of M51 at 500 pc resolution. Below a gas-mass-density of about 5 M_Sun pc^-2, there is a down-turn in star-formation-rate-density which may represent a real local threshold for massive star formation at a cloud mass of about 5x10^4 M_Sun.
July 17th
Maria Cunningham (UNSW)
Title: The chemistry and dynamics of star formation in the G333 molecular cloud complex
G333 Survey is a multi-wavelength survey of the G333 / RCW 106 region, aiming to put together a comprehensive picture of massive star formation throughout an entire giant molecular cloud complex. The aim of the project is to answer observationally some of the key questions about the dynamical processes surrounding massive star formation (e.g. massive stellar winds and large-scale galactic flows) and their relative importance in regulating the star formation process. These dynamical processes drive the turbulent motions which are ubiquitous in giant molecular clouds (GMCs). We have used the new broadband capabilities of the Mopra telescope to map the distribution of around 20 different molecules in an approximately 1 degree square region of the southern Galactic plane (the G333.6-0.2 giant molecular cloud complex). The multi-molecular line nature of this survey is what distinguishes it from similar surveys, and is crucial for gaining a clear picture of the energetics and dynamics of the gas. Different molecular transitions trace different regions of gas in terms of density and excitation, and so can be used to follow energy transfer through the molecular cloud complex. Our initial investigations of the spatial power spectrum of molecules which trace different critical densities show a picture where turbulence is injected at large scales (hundreds of parsecs), and passes through to smaller parsec scales without significant dissipation.
July 10th
ASA
July 3rd @ 11:30am
Howard Yee (University of Toronto, Canada)
Title: The Red-Sequence Cluster Survey
The Red-Sequence Cluster Survey (RCS2) is a 1000-square-degree, multi-color imaging survey carried out using MegaCam on the 3.6m CFHT which is optimized for the search of galaxy clusters at 0.15
July 1st @ 11:30am
Chiaki Kobayashi (ANU)
Title: Chemodynamical Simulations of Galaxies
We simulate the chemodynamical evolution of galaxies using a SPH code that include star formation, supernova feedback, and chemical enrichment from Type II and Ia Supernovae, and hypernovae. (1) In our cosmological simulations, the cosmic star formation rate show a peak at z~4, with ~10% of the baryons turning into stars. The hypernova feedback drives galactic outflows efficiently in low mass galaxies, which eject heavy elements into the intergalactic medium. This mass dependence of galactic winds results in the observed mass-metallicity relation of galaxies. (2) Using GRAPE-SPH simulations of a hundred elliptical galaxies, we discuss the influence of galaxy mergers on the internal structures. Major mergers break the metallicity gradients of progenitor galaxies, and increase the scatter of the fundamental plane. The observed nearby elliptical galaxies cannot be explained by either monolithic collapse or by major merger alone. Rather it requires a model in which both formation processes arise, such as the present CDM scheme.
June 26th @ 11:30am
Terry Bridges (AAO)
Title: HST/Hectospec Study of the Coma Cluster
I'll introduce our multi-waveband study of the Coma galaxy cluster, in particular our HST/ACS Treasury Survey which was awarded 164 orbits in Cycle 15. I'll then discuss early results from a large MMT/Hectospec spectroscopic follow-up program started in 2007, including galaxy metallicities/ages/abundances, and a deep radio luminosity function.
June 24th @ 11:30am
Arif Babul (University of Victoria, Canada)
Title: The Impact of AGN Feedback on Hot X-ray Emitting Gas in Galaxy Clusters
The observed entropy profiles (and by extension, the thermal properties) of the hot X-ray emitting gas in clusters of galaxies show a much greater dispersion than expected if the gas was heated only by shocks associated with infall and mergers. This diversity is best understood as a byproduct of AGN feedback acting on the hot diffuse gas, both before and after cluster formation. Observations suggest that the level of preheating varies from one proto-cluster region to another. The entropy profiles of roughly 50% of the clusters with long central cooling times, the so-called "non-cool core" clusters, require that the gas is "preheated" to high entropy prior to cluster collapse. Those clusters that are not boosted to sufficiently high initial entropies are unstable to cooling and susceptible to massive cooling flows. We have nowdetected star formation in BCGs associated with low entropy systems, indicating that - contrary to today's popular opinion - the gas IS cooling, albeit at a reduced rate. The tempered nature of the cooling flow suggests that AGNs continue to influence the evolution of the intracluster medium even after cluster formation.
June 12th @ 11:30am
David Champion (CSIRO)
Title: The Discovery of an Eccentric Millisecond Pulsar in the Galactic Plane
The evolution of binary systems is governed by their orbital properties and the stellar density of the local environment. Studies of neutron stars in binary star systems offer unique insights into both these issues. In an Arecibo survey of the Galactic disk, we have found PSR J1903+0327, a pulsar with a 2.15-ms rotation period, in a 95-day orbit around a massive companion. Observations in the infra-red suggests that the companion may be a main-sequence star. Theories requiring an origin in the Galactic disk cannot account for the extraordinarily high orbital eccentricity observed (0.44) or a main-sequence companion of a pulsar that has spin properties suggesting a prolonged accretion history. Alternative formation scenarios involve recycling a neutron star in a globular cluster then ejecting it into the Galactic disk, or membership in a hierarchical triple system. Radio timing suggests that the pulsar mass is 1.74+/-0.04 Msun, an unusually high value.
May 15 @ 11:30am
Jarrod Hurley (Swinburne)
Title: Do Globular Clusters Harbour Intermediate-Mass Black Holes?
May 8th @ 2pm
Andrew Melatos (Melbourne Uni)
Title: Pulsar Glitches: Doing Nuclear Physics with LIGO
May 1 @ 11:30am
Philip Lah (MSSSO, ANU)
Title: HI in Galaxies at Moderate Redshifts: Current and Future Observations using Optical Redshifts for HI Coadding
HI in Galaxies at Moderate Redshifts: Current and Future Observations using Optical Redshifts for HI Coadding". It is known that the rate at which stars are produced in galaxies has dropped by a factor of ten in the last 9 billion years (from z ~ 1.0). However, the gas content of galaxies - the fuel supply for star-formation - is only poorly constrained by observations during this period of time. Quantifying the atomic neutral hydrogen gas (HI) content of galaxies using 21 cm emission from distant galaxies (z > 0.1) is difficult with current radio telescopes due to the low flux of the line. However, the average HI content of galaxies at moderate redshifts can be measured by coadding the HI signal from multiple galaxies with known optical positions and redshifts. Our group has been pioneering this technique using the Giant Metrewave Radio Telescope (GMRT) and the Anglo-Australian Telescope (AAT). I will present our current results for the average neutral hydrogen gas content in 121 star forming galaxies at a redshift 0.24 (look-back time of 2.8 Gyr) and the gas content of 324 galaxies surrounding the galaxy cluster Abell 370 at a redshift of 0.37 (look-back time of 4.0 Gyr). I will also discuss the use of the HI coadding technique with the SKA pathfinders and show that they can be used to quantify the average HI content of galaxies out to redshifts of 1.0.
April 15 @ 11:30am
Masami Ouchi (Carnegie Observatories)
Title: TBD
April 11 @ 11:30am
Yashwant Gupta & Jayanta Roy (National Centre for Radio Astrophysics, Pune)
Titles: The Giant Metrewave Radio Telsecope : Status, Science Highlights and Future Plans
and
Development of a Software Back-end for the GMRT
The Giant Metrewave Radio Telescope (GMRT), located near Pune, India, is today a major international facility for work in Radio Astronomy in the frequency range of 150 MHz to 1500 MHz. Consisting of 30 fully steerable antennas of 45 metre diameter each, it can be used as an aperture-synthesis array to produce maps of the radio brightness of extended sources, as well as a phased array with a highly directive beam to study compact radio sources. Each antenna is equipped with multi-frequency feeds and a low noise, high gain heterodyne receiver system, the signal from which is transmitted to a central station using optical fibres. At the central station, multi-purpose back end receivers to process and combine the signals from the 30 antenna stations include (i) a 256 spectral channel correlator and (ii) a phased array combiner followed by a high time resolution pulsar receiver. The sophisticated electronics is backed up with state of the art computing facilities, control and analysis software, to exploit the full capability and versatility of the GMRT. In this talk, we will present an overview of the working of the GMRT. Some of the new and interesting results from the GMRT will also be highlighted. Finally, we will describe the plans for an upgrade of the GMRT, which is expected to significantly increase the scientific potential of the instrument. As part of the upgrade plans, we present the design and implementation of a software back-end for the GMRT. Using primarily COTS components, we have built a 32 antenna, 32 MHz band, dual polarization back-end. This back-end works in a real-time mode, and also supports a baseband recording mode. It will play the dual role of a correlator and a single beam incoherent and phased array pulsar receiver for the GMRT. We present examples of improved data processing that is possible with this software back-end, and highlight possible future applications.
April 10 @ 11:30am
Peder Norberg (IfA, University of Edinburgh)
Title: GAMA: the key to a fundamental Cold Dark Matter model prediction...
The 2 degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey (SDSS) have transformed our view of large scale structure in the low redshift Universe, reinforcing our standard cosmological model: a flat, dark energy dominated collisionless Cold Dark Matter model (\LamdbaCDM). However, neither survey is able to put stringent constraint on a key CDM model prediction, i.e. the shape of the dark matter halo mass function, a crucial component to all hierarchical galaxy formation models. Therefore, we designed the Galaxy And Mass Assembly (GAMA) survey with primary aim to accurately determine the CDM halo mass function over a large mass range. This deep (ten times fainter than SDSS) and wide (~200 sq.deg.) galaxy redshift survey samples the underlying large scale structure with unprecedented detail. In particular, the key scale over which the baryons and baryon physics become critical to our understanding of the structures we see, ie. the 1 kpc to 1 Mpc range, is the one that GAMA probes to an exquiste level. Started in March 08 using AAOmega on the AAT, GAMA has acquired already more than 35k good quality spectra of galaxies, typically ten times fainter than those targeted by SDSS or 2dFGRS. In this talk, I will first overview some of the main results from SDSS & 2dFGRS, emphasizing on both their successes and limitations. This will indirectly lead me towards an outline of the main GAMA science goals. Finally, I will present some preliminary science results using the first 35k spectra of this unique survey.
April 9 @ 11:30am
Bill Smith (President of AURA)
Title: Presentation on AURA
April 4th @ 11:30am
Berkeley Zych (Swinburne)
Title: Clues to the physical environments of CaII QSO absorbers
SO absorption line studies aim to link the properties of galaxies in emission with their gaseous properties, seen in absorption, thus providing an alternative way to study galaxy populations. Whilst still being a far cry from this lofty goal our understanding of QSO absorbers has come a long way over recent years. The most well studied QSO absorbers in this regard are the so-called damped Lyman-alpha systems (DLAs), defined by their large neutral hydrogen column densities (>2.0e+20 atoms/cm^2), which were supposed for a long time to be strongly linked to star-formation, though observational evidence no longer conclusively supports this. Of particular current interest are the much rarer "cousins" of DLAS, strong CaII absorbers, with their unusually high dust-content. There is some evidence that these absorbers are more closely tied with star-formation in galaxies. I wil present the first high-resolution observations of CaII absorbers from which we can glean information about the physical processes occurring in the gas and constrain the chemical and dust-depletion uniformity in these clouds which has repercussions for the presence of molecular hydrogen in these systems and their links to star-formation in galaxies.
April 3rd @ 11:30am
Chris Lidman (ESO)
Title: Adaptive Optics 101: A practical introduction
Adaptive Optics (AO) is a technique that allows astronomers to remove the detrimental effects of turbulence in Earth's lower atmosphere on the image quality of astronomical sources. It is now routinely used at many observatories and has been successfully applied to many areas of astronomy. The Paranal observatory has 8 AO units feeding 6 instruments: NACO, SINFONI, CRIRES, AMBER, MIDI and MAD. Over the next few years, the number and complexity of AO systems on Paranal will increase with the installation of the adaptive secondary on UT4 (for HAWK-I and MUSE) and the high order AO instrument SPHERE on UT3. AO is an integral part of the E-ELT. This talk is a practical introduction to adaptive optics. E.g., what causes seeing, how does AO improve image quality, what is the isoplanatic angle, why do we need laser guide stars, etc. It is meant for anyone who is interested in using AO instrumentation.
March 20th @ 3:00pm
Jochen Liske (ESO)
Title: The Cosmic Dynamics Experiment
The expansion of the Universe, discovered by Hubble in 1929, remains as one of the fundamental observational cornerstones of contemporary relativistic cosmology. The sheer photon collecting power of future Extremely Large Telescopes will allow us, for the first time, to *directly* probe the history of the expansion: by observing a systematic drift of the redshifts of cosmologically distributed sources over the timescale of a few decades we will be able to map out the change of the expansion velocity as a function of cosmic epoch without making any assumptions regarding the physics or possible evolution of the objects involved. This fundamental physics experiment is equally as elegant as it is observationally and technically challenging. In this talk I will describe the experiment in detail, point out some of the difficulties, discuss possible solutions and outline an ongoing effort to devise an instrument capable of meeting the challenge: CODEX.
March 14th @ 2:00pm
Jessica Chapman (ATNF)
Title: ATNF Future Operations
One of the most important issues for the Australia Telescope National Facility today is to plan the changes to operations necessary to implement the strategies for radio astronomy outlined in the 2006 Australian Astronomy Decadal Plan. By 2012 the Australia Telescope National Facility will be operating four world-class observatories; our current facilities, the Australia Telescope Compact Array, the Parkes and Mopra radio telescopes, and the Australian SKA Pathfinder telescope (ASKAP) - currently under development. The ATNF plans for future operations are summarised in a document 'ATNF Future Operations' that is available through the web link below. We are now discussing these plans, as widely as possible, with our user community. In this session I will give a presentation to describe the plans and will then hold a discussion to receive feedback from the audience. To access the document 'ATNF Future Operations', a web discussion forum and other information please see http://www.atnf.csiro.au/observers/planning/
March 13th @ *12:00pm*
Tornado Li (Swinburne)
Title: Finding Galaxy Groups Using Photometric Redshifts
Using a sample of 1212 galaxy groups drawn from the Red-Sequence Cluster Survey (RCS) four-band photometric-redshift catalogs, we study properties of galaxy groups at 0.2 < z < 0.6 and probe group environmental influence on galaxies therein. The galaxy groups are identified using a `probability Friends-of-Friends' (pFoF) algorithm, which is developed specific to search for galaxy groups using photometric redshifts. I will present the algorithm and its tests on mock catalogs. By applying the pFoF algorithm to the RCS sample, we find that red galaxy fractions in galaxy groups decrease with redshift and the rate has a positive correlation with group richness. This `group downsizing' effect is consistent with the group halo mass being a dominant factor in galaxy evolution. The differences among groups of different richness are most apparent in group centers.
March 6th @ 11:30am
Trevor Mendel (Swinburne)
Title: Dynamics of the NGC 5044 group: implications for group galaxy evolution
Groups are now acknowledged to be keystones in the evolution of galaxies, proving to be a necessary link between field and cluster galaxy populations. However, despite the fact that galaxy groups are among the most common structures in the observable universe, our knowledge of mechanisms acting there is limited. I will discuss our efforts to analyse a single group in sufficient detail to reconstruct its evolutionary history, and hence place constraints on pre-processing effects acting in the group environment.
March 4th @ 11:30am
The PILOT Team
Title: The PILOT Roadshow
PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed 2.4m optical/infrared telescope for Dome C on the Antarctic plateau, where the median seeing is 0.3" and the thermal backgrounds 1-2 orders of magnitude below temperate sites. It would be a joint European/Australian facility, with target first light in 2012. The proposed design accomodates both difraction-limited and wide-field seeing-limited observations from 0.4-20um. Key science drivers include Galactic ecology, the oldest galaxies, the most distant gamma-ray bursters, and the equation of state of the Universe. The PILOT Roadshow is intended to spread awareness and initiate creative thought about the unique possibilities of the project. We are also inviting feedback on our strawman design, to ensure that we best meet the science requirements of the community. We will present technical, scientific and political overviews of the project, with plenty of time for feedback and discussion.
February 28th @ 10:30am
Simon Driver (University of St Andrews)
Title: "Galaxy And Mass Assembly (GAMA)"
Galaxies are complex systems containing stars, dust, gas, and plasma. Each of these constituents exhibits distinct structural distributions with significant environmental dependencies. Evidence from the Millennium Galaxy Catalogue (and SDSS) suggests that deciphering galaxies will require both detailed structural and multi-wavelength data coupled with sophisticated modeling of the key physical processes at work. To this end I am attempting to construct a comprehensive high resolution multi-wavelength survey of relatively local galaxies (z<0.5). The resulting database will not only address specific questions pertaining to the nature of dark matter but will also provide a generic resource on the scale of SDSS, and 2MASS. The survey will commence 1st March 08 and has received major allocations of facility time on the AAT, UKIRT, VST, VISTA and most recently Herschel with discussion underway with ASKAP and XMM groups. The final dataset should therefore consist of 200,000 galaxies spread over 250 sq degrees with data for a subset ranging from X-ray to HI.
February 27th @ 11:30am
Darren Croton (Berkeley)
Title: Modeling galaxy formation in the era of large-scale galaxy surveys
Amazing progress has been made in recent years in our understanding of the evolution of galaxies and their connection to the underlying large-scale structure. This has been thanks, in large part, to the quality of galaxy surveys at low and high redshift. This progress looks set to accelerate with upcoming "next generation" surveys. I will discuss simulation and modeling techniques that bridge theories of galaxy formation with the properties of observed galaxy populations. In addition, I will pose a number of open questions important for galactic and extra-galactic astronomy and cosmology, and explain how future large-scale surveys and galaxy formation models may jointly address them.
February 26th @ 11:30am
Lee Spitler (Swinburne)
Title: Constraining early galaxy formation with extragalactic globular cluster systems
Systems of globular clusters constitute one of the oldest, distinct stellar systems observable in galaxies today. Nearly all globular clusters formed approximately 11-13 gigayear ago, hence their properties are sensitive only to the conditions characteristic of this early epoch. I will discuss our efforts to determine the influence of such conditions on the present-day properties of galaxies by contrasting the GC systems in host galaxies of different masses, environments and morphologies.
February 19th @ 12:00pm
Emma Ryan-Weber (Cambridge)
Title: Intergalactic metals at high redshift
It is quite remarkable that less than a billion years after the big bang, metals are observed in the intergalactic medium. For metals to be present, widespread star formation must have occurred at redshifts greater than 8. Observing these metals comes with its own set of challenges, since near-Infrared spectroscopy of faint high redshift quasars is required. During this seminar I will discuss our successful search for triply ionized Carbon (CIV) in the IGM at z~6, together with its implications for the cosmic star formation rate at high redshift, the epoch of reionization, and the role of galactic winds in the Lambda-CMD paradigm.
Jan 17 @ 11:30am
Jean-François Gonzalez (CRAL, Lyon, France)
Title: Dust evolution in protoplanetary disks
We investigate the behaviour of dust in protoplanetary disks under the action of gas drag using our 3D, two-fluid (gas+dust) SPH code. We present the evolution of the dust spatial distribution in global simulations of planetless disks as well as of disks containing an already formed planet. The resulting dust structures vary strongly with particle size and planetary gaps are much sharper than in the gas phase, making them easier to detect with ALMA than anticipated. We also find that there is a range of masses where a planet can open a gap in the dust layer whereas it doesn't in the gas disk. Our dust distributions are fed to the radiative transfer code MCFOST to compute synthetic images, in order to derive constraints on the settling and growth of dust grains in observed disks. Finally, we are adding to our code the processes of particle growth to follow the evolution of dust grains to pre-planetesimals.
Jan 15 @ 11:30am
Laure Fouchet (ETH, Zurich, Switzerland)
Title: Influence of the cooling on the planet migration
Planet migration has been extensively studied analytically and numerically under the two assumptions of an infinitely thin and vertically isothermal disk. These two hypotheses deserve to be questionned. We want to investigate the influence of the equation of state on the rate but also the direction of the planet migration. We compare the two extreme cases of the very efficient cooling (disk vertically isothermal) and inefficient cooling (adiabatic disk). We perform 3D SPH simulations of a protoplanetary disk with a 1 Jupiter mass embedded planet initially located at 5 AU and free to move in response to the disk torques. We use the code GASOLINE with either a vertically isothermal equation of state or an adiabatic one but with including schock heating. We find that the migration behavior is indeed very different in the isothermal and adiabatic case. The planet migrates much more slowly inwards in the adiabatic case than in the isothermal one. We even see an event of outward migration whereas it is always inwards in the isothermal case. The planet never fully opens a gap in the adiabatic case contrarily to the isothermal one. This is because the heated gas expands and achieves a larger scaleheigth, and the Hill radius of the planet is no more of order of the disk scaleheigth. We conclude that a more realistic treatment of the energy equation is required in order to properly describe the planet migration and this could be part of the solution to the too high migration rate problem for planet formation.
Jan 10 @ 11:30am
Leanne Duffy (Los Alamos)
Title: Caustic Rings of Dark Matter
The evolution of cold dark matter in phase-space inevitably leads to the formation of caustics, high density regions in physical space. How significant these high density regions are remains a question. One interesting possibility is presented by the caustic ring model, which studies the accretion of dark matter onto galactic halos. I discuss what a caustic is, present an overview of the caustic ring model and some predictions of the model for the Milky Way halo. The resulting dark matter flows and overdensities may have important consequences for both direct and indirect dark matter detection experiments and I outline some of these implications.