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Second half of 2003

Sep 19 Prof. Robert Deupree (Saint Mary's)
Multi-Dimensional Stellar Structure and Evolution
After a brief introduction to the Institute of Computational Astrophysics, I will outline a number of areas in which multi-dimensional simulations of stars might be expected to provide interesting results. Among these are the treatments of rotation, convection (particularly the time dependent interaction of convection with a time dependent event), and semiconvection. I am currently exploring cases under each of these and will discuss results for the 2D evolution of rotating models, the time dependent behavior of 2D and 3D simulations of convection in the core helium flash, and a preliminary calculation of semiconvection.
Host: John Percy
Sep 26 Prof. George Pavlov (Penn State)
X-rays from Isolated Pulsars and their Pulsar-wind Nebulae
Chandra and XMM-Newton observations of about 50 isolated (nonaccreting) pulsars have provided valuable data on the X-ray properties of these objects. Thanks to the higher sensitivity and better spectral resolution of the Chandra ACIS and XMM EPIC detectors, we can separate the thermal and nonthermal components of their spectra and study the radiation from the neutron star surfaces and magnetospheres with much higher certainty than it was possible in the pre-Chandra era. Particularly important is the high spatial resolution of Chandra data, which allows one to separate the pulsar radiation from that of compact pulsar wind nebulae (PWNe) around young pulsars and study the PWN morphology and spectra. Monitoring observations of the brightest PWNe, around the Crab and Vela pulsars, revealed stunning pictures of their complicated dynamic behavior. I will overview the general X-ray properties of pulsars and PWNe and present most interesting examples of observations of individual objects.
Host: Chris Thompson
Oct 3 Prof. John Dickey (Minnesota)
New features in the inner and outer Milky Way
New surveys of the 21-cm line and continuum emission from the Milky Way disk are finding unexpected structures in the interstellar medium. I will present new data from the Southern Galactic Plane Survey in several areas, including chimneys and supershells traced by the HI gas, spiral features in the far outer disk, scale heights and corrugations of the inner disk, HI self-absorption clouds that appear to be intermediate between the classical diffuse and molecular populations, and structures in the Stokes Q and U emission that are invisible in Stokes I. Overall the new HI surveys of the Milky Way are changing our picture of the interstellar medium and the relationship between the disk and the halo.
Host: Chris Matzner
Oct 10 Dr Jelle Kaastra (Space Research Organisation Netherlands)
X-ray detection of the Warm-Hot Intergalactic Medium
One of the outstanding problems in cosmology is the lack of baryons in the local universe. The major part of the baryons are presently invisible. Recent XMM-Newton observations have shown the presence of the so-called Warm-Hot Intergalactic Medium (WHIM) in the outer parts of four clusters of galaxies. It represents the cool gas that is still falling towards the clusters along filaments, and that radiates in the soft X-ray band after it has been shocked. In this talk I summarize these XMM-Newton results as well as recent attempts to measure the WHIM in absorption towards strong continuum sources using high-resolution X-ray spectra. Finally I discuss the prospects for future instrumentation to detect and characterise the WHIM.
Host: Marten van Kerkwijk
Oct 16
Thu., 3PM!
CITA/DAA		 Prof. Koen Kuijken (Leiden)
Bulges Large and Small
I will describe two projects on the kinematics of spheroids. The first concerns a study with HST of proper motions in the bulge of the Milky Way, which is being used to investigate the orbit structure of the galactic bulge/bar, and the gravitational potential in the central kpc of the Galaxy.
The second part of the talk will present the first results of the Planetary Nebulae Spectrograph project. This is centered around a purpose-built instrument for large-scale measurements of the kinematics of stars in the outskirts of elliptical galaxies, where the dark matter potential is expected to dominate the dynamics. First results are puzzling and intriguing.
Host: Marten van Kerkwijk
Oct 17 Dr Mark Sullivan (UoT)
Tracing cosmic star-formation through time
Determining the precise form of the cosmic star-formation history remains a key goal of modern observational cosmology. In this talk, I will present the latest results from two redshift surveys, selected at UV and radio wavelengths, aimed at tracing the evolution in star-formation in galaxies over the redshift interval 0<z<1. I will discuss the role of dust obscuration, star-formation time-scales and environment in interpreting these and future redshift surveys, and discuss the implications of the survey results for measuring star-formation rates in galaxies at all redshifts.
Oct 24 Dr Lincoln Greenhill (SAO)
X Marks the Spot: The Most Detailed Picture Yet of a Massive Star in Formation
High-mass star formation is not well understood chiefly because examples are deeply embedded, relatively distant, and crowded with sources of emission. We have mapped in detail the structure and proper motion of material 20-500 AU from one of the closest massive YSOs, radio source-I in the Orion KL region. We observe rotating streams of material driven in a wide angle bipolar wind from the surface of an edge-on accretion disk. The example of source-I provides good evidence that massive star formation proceeds via accretion in spite of the effects of radiation pressure.
Host: Yuri Levin
Oct 31 Prof. Ray Carlberg (UoT)
A 30m optical-infrared Telescope for Canada
The scientific argument for a 30m class telescope ranges from the characterization of extra-solar planets to the spectra of "first light" stars to the physics near the event horizon of our Galaxy's super-massive black hole. A 30m class telescope will also be an important complement to the Canadian investments in ALMA, JWST and the SKA. Adaptive optics is the ongoing technical revolution that will allow these telescopes to operate in the diffraction limited regime. Canadians have proposed that they join a project at a "second to none" level that will allow us to play a leadership role in a landmark "big science" facility of the 21st century.
Nov 7 Prof. Ingrid Stairs (UBC)
Searches for New Pulsars
Radio pulsars provide a goldmine of information for astrophysical studies ranging from neutron-star physics to binary stellar evolution to tests of general relativity. Long-term timing observations are the key to much of this science, but the crucial first step is to discover the interesting pulsars. I will discuss two large-scale searches for new pulsars: the Multibeam survey of the Galactic Plane using the Parkes Telescope in Australia, and a deep search of several globular clusters using the Arecibo and Green Bank Telescopes, highlighting some of the most exciting recent discoveries.
Host: Marten van Kerkwijk
Nov 14 Dr David Gilbank (UoT)
The morphologies of faint Extremely Red Objects
Broadband photometric selection is becoming an increasingly common method to identify high redshift galaxies. One particularly powerful technique is to select `Extremely Red Objects' or EROs (systems with unusually red optical minus near-infrared colours) to identify galaxies with a strong decline in their spectral energy distributions at wavelengths around 1 micron. I shall review progress in our understanding of the nature of z>1 galaxies found in this way, discussing the methods available to distinguish different galaxy sub-populations, and focusing primarily on results from a recent morphological survey of faint EROs.
Nov 21 Prof. Ray Jayawardhana (Michigan)
Exploring young brown dwarfs
Brown dwarfs, which straddle the mass range between stars and planets, appear to be common both in the field and in star-forming regions. Their ubiquity makes the question of their origin an important one, both for our understanding of brown dwarfs themselves as well as for theories on the formation of stars and planets. I will present new results from a multi-faceted observational program that provide valuable clues to the formation and early evolution of sub-stellar objects. In particular, based on measurements of disk frequency in the infrared and accretion signatures in the optical, I will discuss whether young brown dwarfs undergo a T Tauri-like phase and if so how long that phase lasts. I will also show that surface gravities and effective temperatures of very low mass objects can be well determined from a multi-feature analysis of high-resolution spectra in comparison with the latest synthetic spectra. Their masses and radii can then be derived by combining observed photometry with synthetic fluxes, inferred gravities and known cluster distances. A couple of our targets appear to have extremely low masses, possibly below the deuterium burining limit. Our results, together with recent detections in other young clusters (by other groups), suggest that 'planemos' may not be rare and raise questions about their origin.
Host: Norm Murray
Nov 28 Prof. Russ Taylor (Calgary)
The Square Kilometre Array
Advances in observation and theory have brought the current generation of astronomers to the brink of understanding the origin and evolution of the Universe. The next major step, to explore the earliest epochs of the evolution of the Universe, before and during the dawn of first light and the creation of stars and galaxies, and to trace the subsequent formation and evolution of primordial galaxies will require a giant telescope operating at radio wavelengths. I will describe plans for a new radio telescope with a collecting area of a square kilometre, 100 times the collecting area of the Very Large Array. I will focus on the Canadian design concept, the Large Adaptive Reflector. I will also discuss plans to build a demonstrator telescope, the Canadian Large Adaptive Reflector (CLAR), later in this decade.
Host: Ue-Li Pen
Dec 5 Prof. Sara Ellison (Victoria)
Mining for metals in the early universe
Quasar absorption line spectroscopy potentially offers an unbiased probe of neutral hydrogen reservoirs from zero to high redshift. In this talk I will summarise the current knowledge of metal enrichment that has been surveyed in the interstellar and intergalactic media via this technique. I will discuss the "missing metals" problem and potential biases in absorption line system surveys due to dust extinction and gravitational lensing. Finally, I will discuss recent work that has allowed us to extend the technique of QSO spectroscopy to probe the sizes and kinematics of the absorbing galaxies.
Host: Marten van Kerkwijk
Dec 12 Prof. Richard Ellis (Caltech)
Exploring the z>5 Universe
Reionisation was a landmark event in the history of the cosmos and piecing together the order of events which led to the young galaxies we now see at redshifts z~5 is a major goal of future facilities. I will discuss various observational techniques which, with existing facilities, may shed light on when the dark ages ended and present early results from each.
Host: Henk Hoekstra
Last modified: 12 Dec 2003, 16:00:03
Marten van Kerkwijk / MP 1404D / 416-946-7288 / mhvk@astro 		Colloquia are Fridays, at 2 PM, in Cody Hall. They are followed by refreshments in the lounge, AB 201.

Instructions for speakers

Schedule with abstracts

Schedule without abstracts

Student seminars

CITA seminars

Physics colloquia

Past colloquia: 2003A, 2003B, 2004A, 2004B, 2005A, 2005B, 2006A, 2006B, 2007A, 2007B, 2008A, 2008B, 2009A, 2009B, 2010A, 2010B, 2011A

Current colloquia: 2011B