University of Toronto Astronomy Colloquia



	ASTRONOMY COLLOQUIA

Fall 2010

Sep 24	Dr. Adam Muzzin (Yale) *The Role of Environment and Self-regulation in Galaxy Evolution at 1 < z < 4* Studies of the local universe have shown that almost any parameter we use to describe a galaxy - color, age, size, morphology, etc. - is correlated with both its mass and environment. In principle, similar measurements at high redshift could distinguish the physical processes responsible for these correlations; however, high-redshift field galaxy surveys such as DEEP2, COSMOS and VVDS have produced conflicting results about the role of mass/environment in galaxy evolution. I will present a new attempt to understand this problem using distant galaxy clusters, the most extreme high-density environments in the universe. The Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS) is a three-year spectroscopic program using the Gemini North and South telescopes that provides highly complete spectroscopy for 10 rich clusters at z ~ 1. Initial results from GCLASS suggest that even in clusters, galaxy formation is primarily self-regulated, with environment playing only a supporting role over long timescales. I will conclude by discussing results from the NEWFIRM Medium Band Survey (NMBS) that show that massive galaxies exist in the field up to z ~ 2 - 4 and still display a bi-modality, which also argues strongly for the self-regulation interpretation.
Oct 05 Tue,12PM Cody Hall	Dr. Alan W. McConnachie (NRC Herzberg Institute of Astrophysics) *Galaxy evolution in the near field with the Pan-Andromeda Archaeological Survey* It is on galactic scales that our understanding of the cosmological evolution of matter is most incomplete. Many of the predicted features of galaxies, such as faint satellites and diffuse stellar haloes, are extremely low surface brightness (>30mag/sq.arcsec). The Milky Way, M31 and M33 are currently the only three large galaxies in the Universe which can therefore provide robust tests of, and constraints on, many fundamental predictions of galaxy formation models. The Pan-Andromeda Archaeological Survey (PAndAS) is a large program using CFHT/MegaCam, that has surveyed nearly 400 sq.degrees in the surroundings of the M31/M33 sub-group, and which is providing the deepest and most complete panorama of galaxy haloes available. This survey has revealed copious stellar streams and substructures, most notable of which is a giant distortion surrounding M33 which helps constrain the orbital history of the Local Group. Large numbers of new dwarf galaxies have been discovered, allowing the derivation of the luminosity function for an entire satellite system to faint magnitudes, and new discoveries of outer halo globular clusters are providing unexpected handles on the accretion history of our nearest galactic neighbor. In addition to reviewing recent results from PAndAS, I will discuss the future development of this field and the facilities it will require, particularly with respect to high resolution wide-field photometry and wide-field spectroscopic capabilities.
Oct 08	Dr. Leisa K. Townsley (The Pennsylvania State University) *Not Your Grandmother's HII Regions: An X-ray Tour of Massive Star-forming Regions* The Chandra X-ray Observatory is providing remarkable new views of massive star-forming regions, revealing all stages in the life cycle of high-mass stars and their effects on their surroundings. We will tour several such regions, highlighting physical processes that characterize the life of a cluster of massive stars, from deeply-embedded cores too young to have established an HII region to superbubbles so large that they shape our views of galaxies. Along the way we see that X-ray observations reveal hundreds of pre-main sequence stars accompanying the massive stars that power great HII region complexes. The most massive stars themselves are often anomalously hard X-ray emitters; this may be a new indicator of close binarity or strong magnetic fields. These complexes are sometimes suffused by diffuse X-ray structures, signatures of multi-million-degree plasmas created by fast O-star winds. In older regions we see the X-ray remains of the deaths of massive stars that stayed close to their birthplaces, exploding as cavity supernovae within the superbubbles that these clusters created.
Oct 15	Dr. Julieta Fierro (UNAM) *Using dance during public lectures* I shall address the different ways that I use in order to convey public understanding of astronomy. I shall emphasize how giving a public lecture including ballet and demonstrations can enrich the experience. Notes added by John Percy: Julieta Fierro is one of the world's best-known and most-honoured astronomy communicators. She is the author of over 40 books, former director of a science centre, and a star of radio and TV in Mexico, as well as a faculty member at UNAM. Her educational and public presentations have always been engagingly theatrical; incorporation of dance is an obvious next step. It is an effective strategy for audiences that do not relate to the standard 50-minute lecture format!
Oct 22	Dr. Wesley C. Fraser (Caltech) *Relics of Planet Formation: Understanding the History of the Kuiper Belt* The small body populations of the outer Solar system such as the Kuiper belt, of which Pluto is a member, are relic objects of incomplete planet growth. As such, these objects are an ideal metric to test and understand the middle stages of planet formation. Two particularly insightful ways to study the Kuiper belt are through its size distribution and the compositions of its members. The size distribution is one of the most fundamental properties of a planetesimal population. As the size of an object is primarily determined from the collisions it has suffered - both disruptive and accretionary - the size distribution holds the key to unlocking the growth and disruption history that ultimately created that population. I will present my latest efforts in measuring the Kuiper belt size distribution, and discuss the belt's virulent evolution these observations imply. In particular, I will show how accretion in the outer Solar system was a very short lived process, most likely halted by the gravitational influence of the gas giant planets which collisionally disrupted and dispersed the primordial Kuiper belt objects from their natal locations, and intermixed populations from different regions of the primordial disk. The compositions of planetesimals is another fundamental property. Past Kuiper belt compositional studies have revealed an astonishingly simple spectral behavior correlated with orbital class, with a frustratingly elusive explanation. I will present the results of a large compositional program I have undertaken with the HST. The results of this program have not only explained the dynamical-compositional correlations in the Kuiper belt, but also provided a link between the observed compositions and the formation history of the belt.
Oct 29	Dr. Mark Reid (CfA) *Measuring the Cosmos* Over 2000 years ago, Hipparcus measured the distance to the Moon by triangulation from two locations across the Mediterranean Sea. However, determining distances to stars proved much more difficult. Many of the best scientists of the 16th through 18th centuries attempted to measure stellar parallax, not only to determine the scale of the cosmos but also to test Heliocentric cosmologies. While these efforts failed, along the way they lead to many discoveries, including atmospheric refraction, precession, and aberration of light. It was not until the 19th century that Bessel measured the first stellar parallax. Distance measurement in astronomy remained a difficult problem even into the early 20th century, when the nature of galaxies ("spiral nebulae") was still debated. While we now know the distances of galaxies at the edge of the Universe, we have only just begun to measure distances accurately throughout the Milky Way. I will present new results on parallaxes and motions of star forming regions and the compact object at the center of the Milky Way. Using the Very Long Baseline Array we now can achieve positional accuracy approaching 10 micro-arcseconds! These measurements address fundamental problems in Galactic dynamics, evidence for supermassive black holes, and the mass of the dark matter halo of the Milky Way.
Nov 02 Tue,12PM	Dr. Tom Williams (Rice) *Four years determine an astronomer's life: Leon Campbell at the Boyden Station* As the discipline of astrophysics crystallized late in the nineteenth century, Edward Charles Pickering, Director of the Harvard College Observatory (HCO), established as the basic mission of that institution, the standardization of basic astrophysical techniques, photometry and spectroscopy. Pickering then devoted the HCO’s assets to the application of those techniques to create large catalogs of standardized astrophysical data (magnitudes and spectral classifications), for stars across the entire sky. Pickering established the Boyden Station near Arequipa, Peru, to provide most of the necessary raw data from which such massive catalogues could be constructed for both the northern and southern hemispheres of the sky. A young Leon Campbell supervised the operation at Boyden Station for four years from 1911 to 1915, a period during which the course of the remainder of his fifty year career was largely determined. This talk will consider the evolution of astrophysics during that period and Campbell’s career at HCO that followed his experience at Arequipa. The story of Campbell’s life and as one of the earliest astronomers to make a career in variable star astronomy emerged as part of the research for the centennial history of the American Association of Variable Star Observers.
Nov 12	Dr. James Di Francesco (NRC-HIA) *Herschel Studies of Star Formation* The Herschel Space Observatory is a 3.5 m diameter telescope launched in 2009 by the European Space Agency to study the cold aspects of the Universe through observations of far-infrared and submillimetre continuum and lines. (Canada participates in this mission through the Canadian Space Agency.) The sensitivity of Herschel to the thermal emission from dust at temperatures < 50 K without any atmospheric absorption makes Herschel an excellent probe of the dense structures within molecular clouds that will eventually form stars. In this presentation, I will highlight many of the early results relevant to star formation from Herschel, in particular those from the low-mass "Gould Belt" Key Project and the high-mass "HOBYS" Key Project. These studies have already revealed very detailed censuses of dense cores within a few key regions. In addition, the locations of such structures within apparently supercritical filaments suggest it is the processes that form of such filaments that ultimately produce stars. In addition, prospects of future observations from these projects will be described.
Nov 19	Prof. John D. Monnier (University of Michigan) *Karl Kamper Memorial Lecture: Imaging the Surfaces of Stars* Under the best conditions, telescope diffraction limits the angular resolution for astronomical imaging. Using interferometry, we can coherently combine light from widely-separated telescopes to overcome the single-telescope diffraction limit to boost our imaging resolution by orders of magnitude. I will review recent technical and scientific breakthroughs made possible by the Michigan Infrared Combiner of the CHARA Array on Mt. Wilson, CA, with baselines of 330 meters allowing near-infrared imaging with sub-milli-arcsecond resolution. I will highlight the first resolved images of main sequence stars besides the Sun, focusing on the oblate and gravity-darkened photospheres of rapidly rotating stars. We can now also resolve the interacting components of close binary stars for the first time and I will give an update on the remarkable on-going eclipse of epsilon Aurigae.
Nov 26	Prof. Kristen Menou (Columbia University) *Exoplanetary Atmospheres* Comparative planetology now encompasses a large set of extrasolar planets. Recently, direct constraints on the atmospheres of a number of exoplanets have become available. I will briefly describe the observational status of this field. I will then report on various efforts to interpret these observations in terms of atmospheric responses to unusual forcing conditions, well beyond the ones found in the Solar System. The future of the field is exciting, with potentially habitable terrestrial planets on the horizon.
Dec 03	Dr. Anne-Marie Weijmans (Dunlap Institute for Astronomy & Astrophysics,U of T) *Evolution, classification and dark matter in early-type galaxies* The Atlas3D project is a survey of a complete sample of nearby early-type galaxies with the integral-field spectrograph SAURON, complemented with auxiliary datasets (imaging, CO, HI) and simulations. In this talk I will give an overview of this large program and discuss some recent results on galaxy evolution and classification. I will then focus on one of the projects that we are undertaking within the Atlas3D program, which is the study of dark matter haloes around early-type galaxies, using wide-field integral-field spectrography.
Dec 10 12PM	Dr. Annette Ferguson (Royal Observatory Edinburgh) *Unveiling the Outer Regions of Disk Galaxies* The last decade has seen remarkable advances in our ability to probe the structure and content of galaxies to extremely low surface brightness levels. Studies have revealed that the baryonic components of galaxies are far larger than previously thought and that galactic peripheries contain a variety of complex stellar structures on both small and large scales. My talk will highlight some recent results on galaxy outskirts derived from deep HST pencil beam and wide-field ground-based studies of galaxies within and beyond the Local Group. Inferences on disk galaxy assembly drawn from these studies will be compared to theoretical expectations, as well as the picture emerging from the distant Universe.(Pleae note the colloquium will start at noon, revised time is 12:00pm to 1:00 pm)
Dec 17	Dr. Preethi Nair (PDF, INAF-Astronomical Observatory of Bologna) *The Impact of Secular Features On The Evolution Of Disk Galaxies* The role of bars in driving secular evolution of galaxies is still highly debated. The fraction of barred galaxies both in the local and high redshift universe are highly debated as well as their role in building bulges and triggering AGN. In this talk, I will present some recent results from studies in the low redshift universe with SDSS and at high redshift with data from the COSMOS survey.

Last modified: 07 Sep 2011, 10:42:27

Marten van Kerkwijk (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

Physics colloquia

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

Current colloquia: 2011B