Astronomy and Astrophysics
|Astronomy faculty members with the SHARC-NET supercomputer. From left to right, Doug Welch, Alison Sills, Ralph Pudritz, Hugh Couchman, Christine Wilson, Bill Harris, Peter Sutherland||
Astronomy and astrophysics today is in the midst of a worldwide golden age of discovery that will continue far into the new century. How did the giant structures called galaxies actually form in the early Universe? How do the gaseous clouds within a galaxy condense into stars, and how does a galaxy evolve over time? What is the age and history of our own Galaxy? What types of planets are common around nearby stars? Benefitting from remarkable advances in telescope technology, instrument design, computing techniques, and software for data analysis, modern astrophysics combines many branches of physics, mathematics, and computing to explore the universe beyond the Earth.
The Astrophysics Group at McMaster provides a wide range of expertise and a vital research environment for staff, graduate students, postdoctoral fellows, and visiting colleagues. All of its faculty members, whose research interests are listed below, are national and world leaders in their subdisciplines, and have extensive links with other groups and international organizations in astronomy.
Hugh Couchman is a theoretical cosmologist who uses numerical simulations to investigate the way that cosmic structure (galaxies, clusters of galaxies, and superclusters) built up from small density fluctuations in the pre-galactic gas, beginning at a time roughly 100,000 years after the Big Bang and working forward to the present day 10 billion years later. New telescopes both in space and on the ground are providing a wealth of new data to constrain these simulations and thus to understand the initial conditions from which these vast structures arose. Hugh is a CIAR Fellow, and has recently been awarded a Premier's Research Excellence Award .
|Cosmological simulation of structure growth in an expanding cold dark matter universe.|
William Harris is an observational astronomer who studies the formation and evolution of the oldest visible structures in galaxies -- globular star clusters and galactic halos. For globular clusters within our own Milky Way galaxy, the application of physical models for stellar evolution allows us to put precise limits on the true ages of these ancient star clusters. For other galaxies, particular giant and supergiant ellipticals, the huge numbers of globular clusters that can be found in them give us some of our most prominent visible clues to the way these galaxies assembled. He and his colleagues and students make extensive use of large telescopes around the world, including the Hubble Space Telescope, to obtain deep imaging data for these remote galaxies.
|A portion of the inner halo of NGC 5128, the central giant elliptical in the Centaurus group of galaxies. This image, constructed from Hubble Space Telescope data taken by Bill Harris (McMaster) and Gretchen Harris (Waterloo), gives the first star-by-star look into the inner regions of a giant elliptical galaxy. The bright object at lower left is a globular cluster in NGC 5128.|
Ralph Pudritz is a theoretical astrophysicist who studies the formation of stars both in the local interstellar medium, and in the context of galaxy formation. Stars form as members of star clusters within self-gravitating, cold, and magnetized molecular clouds in galaxies. He and his students have constructed models for clouds, cluster formation, gravitational collapse, and jets and outflows from protostellar disks. They also use sophisticated numerical simulations to chart the formation and evolution of protostellar jets. His current research interests include the formation of planetary systems within protostellar accretion disks. He is also applying the physics of star formation to the study of star formation in protogalaxies - the formation of globular clusters systems being one example. He collaborates with observational astronomers in the group and elsewhere in order to constrain models with good data. Ralph was also the chair of the Long Range Planning Panel which charted the future of Canadian astronomy to 2015.
|Jet and disk in the protostellar object HH30. Image taken by the Hubble Space Telescope.|
Alison Sills is a theoretical astrophysicist whose research interests involve applying our understanding of stellar evolution to a variety of astrophysical problems. In particular, she models the unusual stellar populations in globular clusters, especially those arising from stellar collisions. By understanding the properties of the stellar collisions and the stars that result from such interactions, we can determine the evolution of globular clusters. Some of her other research interests include rotation in stars, extra-solar planets, and binary star systems. Alison is a recipient of a NSERC University Faculty Award.
| A collision between two main sequence stars.
(click on image to play movie -- 2.5Mb mpeg)
Peter Sutherland has his research interests in the modelling of physical processes in pulsars and supernovae, as well as in the numerical codes for radiative transfer models and dynamics. Supernovae, the explosive disruptions of entire stars, are the most violent events stars can undergo, and there are many open questions about the details of the explosion and the subsequent release of radiation as the ejecta expand and thin out.
|Hubble Space Telescope image of Supernove 1987A, showing the evolution of the ejecta with time.|
Doug Welch carries out research in the nature of variable stars and the calibration of the extragalactic distance scale, principally using classical Cepheid variables. In the past few years, he has worked extensively with the MACHO Project, a large-scale international program to survey millions of stars and search for the elusive "dark matter" candidate objects in the halo of our Galaxy. His most recent work has been studying Cepheids in eclipsing binary systems in the Large Magellanic Cloud, double-mode Cepheids and RR Lyrae stars, and the frequency and nature of the so-called Blazhko Effect in fundamental and first overtone mode RR Lyrae. Also, he has on-going collaborations with workers studying the nature of variable stars in globular clusters in our own galaxy with unusual combinations of horizontal branch morphologies and variable star populations.
A lightcurve of an RR Lyrae star showing a Blazhko effect variation -- a change in the shape of the normal lightcurve with a period of a few months.
Christine Wilson carries out observational research in star formation and the interstellar medium, both in our own Galaxy and other nearby galaxies. She and her students frequently use the James Clerk Maxwell Telescope and the Caltech Millimeter Array to study young protostars and structures within nearby molecular clouds, and the relationship between the interstellar medium, star formation, and galactic structure in dwarf galaxies, barred galaxies, and interacting galaxies. Christine is the Canadian Project Scientist for ALMA and has recently been awarded a Premier's Research Excellence Award.
|Polarization of the light coming from the Orion Molecular Cloud star forming region. Data taken with SCUBA at the JCMT.|
The observational astronomers in the group (Harris, Welch, Wilson and their students and colleagues) make extensive use of modern tools such as CCD detectors for photometry and spectroscopy, infrared arrays, multiobject spectrographs, and millimeter-wave interferometers. To collect measurements of the objects they are studying, they frequently travel to visit remote observatories such as the Canada-France-Hawaii Telescope and James Clerk Maxwell Telescope (both on Mauna Kea, Hawaii); the new Gemini twin 8-meter telescopes in Chile and Hawaii; and other sites in Chile, Australia, and the southwestern USA. The Hubble Space Telescope and other new satellite observatories are also seeing increasing use within the group. Graduate students at McMaster learn to use all these facilities in close contact with their supervisors, in ways that are designed to match with their particular thesis research projects.
|Professors Christine Wilson, Doug Welch, and Bill Harris in the control room of the Canada-France-Hawaii Telescope on the summit of Mauna Kea, Hawaii.|
Astrophysics theory students at McMaster can expect to take advantage of close links with the Canadian Institute for Theoretical Astrophysics (CITA), frequent in-house seminar series and ongoing workshops, and an outlook to research which encourages both wide and deep thinking. We operate with the view that most important modern astrophysical problems require a simultaneous assault on both the observational and theoretical fronts. Our program is specifically designed to produce graduates who will be well-versed in both theoretical and observational issues, and not just in a single speciality of one of the faculty members.
Our recent PhD and MSc graduates have had fine success at continuing on in both astrophysics research and other intellectually challenging fields. One of our PhD students was awarded the Plaskett Medal for the best astronomy thesis in Canada. Three PhD grads have been offered Hubble Fellowships, one is on the faculty at Rutgers, one has obtained a position at the Niels Bohr Institute in Denmark, one went to a staff position at the Canada Center for Remote Sensing in Ottawa, and many others can be found at observatories and universities across the USA and Canada.
Although our group is well linked nationally and internationally to astronomy resources around the world, we have devoted considerable effort to building local resources. A sophisticated computing environment is an essential part of our research and training program, built on an extensive network of fast workstations and hundreds of Gbytes worth of disk space that are shared among all users in the group. We are also one of the driving forces in high-performance supercomputing on campus, and are the major users of the local SHARCnet node, a 112 processor COMPAQ AlphaServer SC40. We are committed to constantly upgrading these facilities, and graduate students here will enjoy access to modern hardware that is unexcelled at any other institution in the country.
|McMaster offers outstanding opportunities for graduate studies in forefront astrophysics. We strongly urge that you come to visit, take an informal tour of our facilities, and discuss science with us.||