Introduction:
This year, York University, Canada's third largest university, is celebrating its 40th anniversary. The Department of Physics and Astronomy, a component of the Faculty of Pure and Applied Science at York, currently has a complement of six full-time professors. In order of joining the Department, these professors are Kim Innanen, Wayne Cannon, Michael De Robertis, John Caldwell, Marshall McCall and Norbert Bartel. Paul Delaney arrived at York in 1986 and is currently a senior lecturer. Ralph Nicholls, though retired, continues as a member of the graduate programme. Robin Kingsburgh, Slavek Rucinski and Nancy Evans are adjunct faculty members of the graduate programme. Both Kingsburgh and Rucinski are currently supervising graduate students in the Department. Paul Wiegert, a Research Associate and CITA National Fellow, Michael Bietenholz, a postdoctoral fellow, and several graduate students round out the astronomy group at York.
The Department offers astronomy streams in both the undergraduate and graduate programmes. Emphasis in all years is placed on observing using the 30 and 60cm telescopes that are computer controlled (with a 40cm telescope soon to arrive). The observatory co-ordinator, Paul Delaney, has a mounted a successful public outreach campaign using these facilities that draws over 4,000 visitors each year. Moreover he co-ordinates an active research programme on variable stars with the 60cm in conjunction with graduate student Mel Blake and student volunteers.
The Department teaches astronomy to about 500 Arts and Fine Arts students, between 150-200 first-year science students, as well as a few dozen upper-year students. For the past few years, one of the largest and most successful clubs on campus has been the Astronomy and Physics Club. There is also a very active space-science or SEDS (Students for the Exploration and Development of Space) chapter.
Given the special nature of this issue of the newsletter, some members of the Department have provided a personal retrospective on their career at York, while others have provided a summary of their current research interests.
Recollections of Kim Innanen:
It may be interesting to begin with the comment that my first fulltime academic position, at Western, was in the (then) Department of Mathematics and Astronomy. My background with the first digital computers at Waterloo, and my doctoral work at Toronto had made me comfortable with numerical/computing work. In addition to joining Bill Wehlau to teach courses in Astronomy, the department head (in those days), a mathematician, was anxious to have a course taught in Numerical Analysis. I'm sure that my ready acceptance of that responsibility contributed directly to getting the position. During the following three years at Western, I didn't interact much with physicists at Western, save for one: Ralph Nicholls, with whom I chatted occasionally over lunch at the Faculty Club. Sandra (MA in astronomy, Toronto) and I were engaged, and following our marriage, she found employment as one of Ralph's research assistants. In 1965, Ralph went off to take up his new position at York. This background is relevant for two reasons: obviously, because Ralph and I came to know each other, he knew that I could teach mathematics as well as astronomy, and finally, the clincher: in order to keep his fine research assistant and bring her to York, it was necessary to hire this astronomer!
So it goes. At York, in 1966, all of the scientists worked in the new Farquharson Building. The Steacie Science Library was also completed. My initial responsibilities were two-fold: to teach mathematics courses to the science undergraduates and to help complete the architectural decisions relating to the Astronomical Observatory to be attached to the planned, new science building, later named for R.M. Petrie. Ralph, of course, had been intimately involved with the earlier decision to have an observatory attached to this building.
I recall some of my comments confirming the option to have the observatory as a detached, but bridged, structure from the main building, so as to keep it more vibration-free. It was also decided that there should be two telescopes: one for teaching, and the other for research. My other significant duty was to assist in the purchase of telescopes for the two domes. This was somewhat new territory for me (although in the early, sixties, all graduate students in astronomy at Toronto, even theoreticians, had to take a weekly, half-night shift in the observing program, in those days managed by Sidney van den Bergh. I had also learned some of the practical matters of telescope selection from Bill Wehlau, then choosing the newly funded 1.2m reflector at Western). When one is young, one can just forge ahead and even grasp less familiar territory with equanimity. In his travels to Boston, Ralph had become familiar with a successful high-end automobile shop called Competition Associates. Its owner (a David Brown, I believe) had also become involved in making telescopes. Thus it was that when I arrived at the shop to take a look, I remember the interesting sight of the two, white York telescopes-to-be nestled amongst a colourful collection of Ferraris, Maserattis, Porsches etc. A very attractive purchase deal was struck soon thereafter for both reflectors, one a 30-cm, the other a 60-cm. It was also necessary to purchase domes for the observatory, a pair of off-the-shelf Ashdomes. Following installation, they were painted white, and the observatory exterior quickly became a popular photographic feature on many York publicity releases.
In due course, it came time to take delivery of our two telescopes. They arrived, fully assembled, under canvas, on a massive flatbed truck one very cold, windy, January day, escorted by Mr. Brown. We had booked a huge crane to lift the entire telescopes very high, about 30 m; with the help of a portable walkie-talkie, the excellent crane operator eased them through the open dome slits, and set them down on their piers. I was quite relieved when this process was completed, especially because the available clearance for the larger telescope was just a few cm. For reasons of architectural aesthetics, the domes were of the same size. As a result, it became necessary to add a specially designed, fenced platform to allow safe student access to the smaller telescope. Later, we added lifting/lowering facilities to permit removal of the larger mirror for re-aluminizing, done at the DDO. From those earliest days, the Faculty mechanical and electrical shops have been intimately involved in keeping the observatory operational. The telescopes performed extremely well optically and mechanically, but their electronics required significant upgrades. Only recently has the smaller telescope been retired for a more modern one. Soon after this start-up phase, it was possible for me to fade into other matters, for Stanley Jeffers arrived and took up most of the observatory burdens. I was, however, involved in initiating the observatory public visits, a feature which continues to this day. It was also very pleasant to have Chris Purton join us as our resident radio astronomer, and with whom we sponsored a number of postdocs including Alan Wright, Martin Clutton-Brock and Paul Feldman.
Reflections of Wayne Cannon:
Wayne Cannon began a program of VLBI activities at York University in 1972 when he moved from a postdoctoral position at Cal-Tech and accepted a position as an Assistant Professor in the Department of Physics and Astronomy (then the Department of Physics only). This work involved a collaboration with the VLBI group at NRC led by Dr. N. Broten and Dr. T.H. Legg as well as the VLBI group at the University of Toronto led by the late Professor J.L. Yen in the Department of Electrical Engineering. This work was carried out with the early Canadian "analog" VLBI system on baselines between ARO, Owens Valley, and Chilbolton England.
In the late 70's and early 80's support for this VLBI activity was also provided by the Geodetic Survey Division of the Surveys and Mapping Branch as well as the Geophysics Division of the Earth Physics Branch of NRCan (then EMR). When it was apparent that NRC would soon no longer support the old analog VLBI system a collaboration was begun between York University, the University of Toronto, NRC, and the two Divisions within NRCan (EMR) to develop an experimental, digital VLBI system which carried out the delay and Doppler corrections upon recording at the stations. This VLBI system, since dubbed "System-1" or the "S1" VLBI system, had a maximum data rate of 24 Mbit/sec and produced its "first fringes" (analogous to "first light" at an optical observatory) at the correlator facility built in the basement of the Petrie building at York University in the mid-80's.
The development in the late 70's of the 112 Mbit/sec "MkIII" VLBI system and the follow-on 128 Mbit/sec "VLBA" VLBI system made it clear that the 24 Mbit/sec "S1" system was outmoded and work was begun in 1988, under the leadership of W.H. Cannon founder and present Director of the Space Geodynamics Laboratory (SGL) of the (then) newly established Institute for Space and Terrestrial Science (ISTS) on the campus of York University, on the development of the 128 Mbit/sec "S2" VLBI system. This effort was soon joined, with support of the Canadian Space Agency, by a group at the Dominion Radio Astrophysical Observatory (DRAO) under the leadership of Peter Dewdney in development of an S2 VLBI correlator facility for use in space VLBI missions, the Russian-led RadioAstron and the Japanese-led VSOP.
In the late '80's NRC withdrew support for the operation of the 46 m antenna of the Algonquin Radio Observatory and SGL, on the campus of York university, in collaboration with the Geodetic Survey of NRCan has kept the facility open for VLBI for more than 10 years. ARO is now one of the premier sites defining the International Terrestrial Reference Frame (ITRF) and the International Celestial reference Frame (ICRF).
The "S2" VLBI system has gone on to become a "world standard" VLBI system with as many as 55-60 systems at work in radio astronomy at observatories and correlator facilities in more than a dozen countries. The S2 system is shouldering the research work involved in the "sky survey" portion of the VSOP space VLBI mission underway today. Work has begun at SGL on the campus of York University on the development of the advanced "S3" 1024-2048 Mbit/sec (1-2 Gbit/sec) VLBI systems which will succeed the S2 and is expected to find use in future space VLBI missions.
Michael De Robertis:
Michael De Robertis arrived at York from Lick Observatory in late 1985 as a University Research Fellow, a programme once sponsored by the Natural Science and Engineering Research Council. His interests at that time were primarily in the area of the spectroscopy of active galactic nuclei. He and his students have a particular soft spot for Seyfert galaxies. Interactions with the "local group," however, soon led him into the fascinating areas of studying the environments of various classes of active galaxies, detecting primeval galaxies, as well as a variety of observational problems involving Galactic Structure, including the characteristics of low-mass, metal-poor stars.
Somewhere along the line, perhaps the result of being the Chair of the Local Organizing Committee for the 1991 Canadian Astronomical Society at York University, he became a member of CASCA Board.
John Caldwell:
John Caldwell came to York in the summer of 1986. Plans for the move had been established for some time, and it was expected that he would begin his research career here working on the Space Telescope (later known as the Hubble Space Telescope). He had been working on the ST program since 1977, and the launch was scheduled for late 1986. The tragic explosion of the NASA Challenger spacecraft in January, 1986, with the loss of seven lives, led to extensive delays in all shuttle launches, with the HST finally being launched successfully in 1990. After a couple of well publicized problems, including the infamous "spherical aberration" fiasco, the program settled down to do steady and increasingly spectacular science, as fixes were made and experience was gained. In the first days of the HST, planets were among the favourite targets, because their brightness relative to other celestial objects meant that planetary images were more successfully deconvolvable than extrasolar ones. To this day, planetary astronomers are convinced that the HST owes its survival, during the time when it was the cartoon joke of the day in every media outlet on the planet, to the magnificent images of Mars, Jupiter and Saturn which made credible the early postlaunch claim that Hubble would rise above is inauspicious beginning and become the wonderful success that it is today.
Caldwell was also the director of the Space Astrophysics Laboratory of the Institute for Space and Terrestrial Science, an Ontario Centre of Excellence funded by the provincial government. The Laboratory was operative from 1988 to 1994, during which time it attracted an extremely able complement of professional scientists, including Drs. Christopher Barnet, Cindy Cunningham, Nancy Evans, Xin-Min Hua and Slavek Rucinski. Sadly, the Laboratory was terminated by new management in 1994, when the bottom line became the bottom line. It was judged that the SAL was not sufficiently tied to industrial output to merit continued support. Management drove home the point by renaming the Centre as the Centre for Research in Earth and Space Technology. As confirmation that the science staff of the SAL, named above, really was as good as the director thought and thinks they are, four of the five went on immediately to work in other high profile space astronomy or space science missions. The fifth was unable to relocate because of family commitments, and went to work for another branch of the Ontario government. But members of CASCA who may be contemplating robbing a convenience store in Ontario will be comforted to know that their video picture will be deconvolved by an astronomer who learned how while saving Hubble.
Marshall McCall:
Marshall McCall arrived at York in 1988. He and his students blend observation with theory to study the formation, evolution and distribution of galaxies.
With M. De Robertis, a novel technique has been developed and applied to search efficiently for primeval galaxies. The advantage of the technique is that it is sensitive to spectral signatures of primeval galaxies over a wide range of redshift.
To study galaxy evolution, HII regions and planetary nebulae are used to probe how stellar birth and death rates and the chemical state of matter vary from place to place within a galaxy and from galaxy to galaxy. Most recently, McCall and collaborators M. Richer and G. Stasinska have been able to elucidate how elliptical galaxies evolved prior to the epoch of rapid gas loss. The work has led to estimates for the total masses of the clouds out of which elliptical galaxies formed, and to a means for evaluating how much gas ellipticals have contributed to the intergalactic medium. Ph.D. student H. Lee has discovered several gas-deficient dwarf irregular galaxies in the Virgo Cluster. Based upon their chemical properties, it appears that whatever mechanism depleted the gas in these galaxies acted over a time scale which was short compared to the time scale for chemical evolution. With R. Straker and R. Kingsburgh, a technique for automatically deriving unbiased luminosity functions for HII regions has been developed. By requiring the integration boundary to be at a fixed fraction of the peak surface brightness of an HII region, luminosity functions become directly linked to the distribution of stellar luminosities in embedded OB associations.
McCall and collaborators R. Buta, K. Innanen, and M. Valtonen are also pursuing research to examine how the Milky Way came to be where it is today. Dynamical simulations of the motion of the Milky Way relative to its neighbours are carried out to evaluate its path through space since the Big Bang. Besides helping to pin down the reason why we are falling towards the Andromeda galaxy, constraints on the age of the universe and the total mass of the Milky Way, dark and light, follow. The work has required detailed study of the local organization of galaxies, especially elucidation of the structure of the Local Sheet, as well as the development of a coherent system of weighing galaxies to pin down the relative masses needed for the simulations. Most recently, a photometric survey of the nearby heavily-obscured IC~342/Maffei group has been completed. After successfully removing the tens of thousands of stars contaminating the fields, three of the galaxies were shown to be among the largest and brightest in the northern sky. Work is in progress to assess the impact of the group on the dynamical evolution of the Local Group.
Norbert Bartel:
Norbert Bartel joined York University as a Professor in the Department of Physics and Astronomy in 1992 after 10 years as a research associate at Harvard University. His scientific interests are focused on galactic and extragalactic compact radio sources such as supernovae, pulsars, black hole candidates, radio stars and the powerful cores of radio galaxies and quasars. With the technique of very-long-baseline interferometry (VLBI) and a network of several large radio telescopes girdling the globe these sources are imaged and their positions determined with an angular resolution and precision more than 1,000 times better than with any optical telescope on Earth.
In particular he leads a project on supernova VLBI. A sequence of images of a young, rapidly expanding supernova is made, the interaction of its shock front with the circumstellar medium is studied and a pulsar is searched for in the centre. The results are composed in a fully animated movie "Supernova - Death of a Star." The movie is aimed to be appropriate for a scientific audience as well as the general public. The first version was recently chosen to represent scientific results from the Very Large Array for inclusion in a promotion movie of the Tourist Department of the State of New Mexico.
His other main project is geared towards the VLBI support of the spaceborne relativity mission, Gravity Probe B, to be launched in 2000. This mission is being developed by NASA and Stanford University, whose goal is to monitor the precessions of on-board gyroscopes with respect to a bright guide star to test two predictions of general relativity. With VLBI, the guide star's proper motion is determined with respect to distant quasars so that the precessions can be referred to a (quasi) inertial reference frame and determined up to 10,000 times more accurately than ever before.
HIA
University of Calgary
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