CASCA 2000 - Abstracts of Talks & Posters

O-01 Halo Dark Matter Searches: If it's not Dark it Doesn't Matter

D. Scott, University of British Columbia

Dark matter continues to be a mysterious and beguiling theme running through modern astrophysics. There are now three distinct dark matter problems: (1) what are the un-shiny baryons? (2) what is the cold particle matter? (3) what is the dark energy? I shall discuss some progress in attempts to illuminate each of these puzzles. A partial answer to the first question may come from recent evidence (including our study of the Hubble Deep Field) that there may be more dead stars around than previously believed, so that faint blue dwarfs could be some of the dark matter. However, this raises some more detailed issues, such as: what is the spatial distribution of this new population? how much of the baryons can be accounted for? could this provide fossil evidence of early star formation in our own and other galaxies?

O-02 Disruption Timescale of Dark Matter Halos

E. Hayashi and J. F. Navarro, University of Victoria

Numerical simulations are used to investigate the dynamical evolution of dark matter satellites in orbit around larger halos. The effects of varying mass resolution, force resolution, orbital type (circular or elliptical) and tidal radius are explored in a series of simple n-body simulations. Changes in the density profile and self-bound mass of satellites with time are compared with the predictions of an impulse approximation model. These results are applied to cosmological simulations in an attempt to predict the disruption timescale of dark matter subhalos in clusters.

O-03 Dark Matter Distribution in Galaxy Disks

S. Courteau and H.-W. Rix, University of British Columbia

I review existing measurements of the dark matter distribution in disks of spiral galaxies, and address which of the stellar disk or the dark matter halo dominates the potential in the central parts of spiral galaxies. I conclude, contrary to previous assumptions of "maximal disks", that dark matter dominates at all radii in faint and bright (non-barred) galaxies.

O-04 CFHT Weak Lensing Survey: A First Glimpse into the Cosmic Web

G.G. Fahlman, CFHT

(Abstract not available at press time)

O-05 Galaxy Clustering Evolution in CNOC2

R.G. Carlberg, H.K.C. Yee, S.L. Morris, H. Lin, P.B. Hall, D. Patton, M. Sawicki, and C.W. Shepherd, University of Toronto

The redshift evolution of the galaxy two-point correlation function is a fundamental cosmological statistic. To identify similar galaxy populations at different redshifts, we select a strict volume-limited sample culled from the 6100 cataloged CNOC2 galaxies. This subsample contains about 2300 galaxies distributed between redshifts 0.1 and 0.65 spread over a total of 1.55 square degrees of sky. A similarly defined low-redshift sample is drawn from the Las Campanas Redshift Survey. We find that the co-moving two-point correlation function can be described as xi(r|z) = (r₀₀/r)^gamma(1+z)^{-(3+epsilon-gamma)} with r₀₀=5.03 ± 0.08 hmpc, epsilon=-0.17±0.18 and gamma=1.87 ± 0.07 over the z=0.03 to 0.65 redshift range, for Omega_M=0.2, Lambda=0. The measured clustering amplitude and its evolution are dependent on the adopted cosmology. The measured evolution rates for Omega_M=1 and flat Omega_M=0.2 background cosmologies are epsilon=0.80 ± 0.22 and epsilon=-0.81±0.19, respectively, with r₀₀ of 5.30 ±0.1 hmpc and 4.85 ± 0.1 hmpc, respectively. The sensitivity of the derived correlations to the evolution corrections and details of the measurements is presented. The analytic prediction of biased clustering evolution for only the low density, Lambda_CDM cosmology is readily consistent with the observations, with biased clustering in an open cosmology somewhat marginally excluded and a biased Omega_M=1 model predicting clustering evolution that is more than 6 standard deviations from the measured value.

O-06 Unveiling Dwarf Galaxies in Low Redshift Galaxy Clusters

W.A. Barkhouse, H.K.C. Yee and O. Lopez-Cruz, University of Toronto

We have recently completed a comprehensive photometric survey of 27 Abell clusters (0.02 < z < 0.04) with the 8k mosaic camera on the KPNO 0.9m telescope. The dwarf galaxy population has been characterized by constructing luminosity functions, measuring spatial variations, dwarf-to-giant galaxy ratios and colour distributions. Preliminary results for several galaxy clusters will be presented.

O-07 Techniques in High Resolution Observations from the Ground and Space and Imaging of the Merging Environments of Radio Galaxies at Redshift 1 to 4

E. Steinbring, University of Victoria

I discuss several techniques that help overcome the limitations of adaptive optics (AO) observations with existing instruments in order to make them more comparable to imaging from space. For example, effective dithering and flat-fielding techniques as well as methods to determine the instrumental point-spread function. The implementation of these techniques as a software package called AOTOOLS is discussed. I also discuss computer simulations of AO systems, notably the Gemini North Telescope Altair instrument, in order to understand and improve them. I apply my AO image processing techniques to observations of high-redshift radio galaxies (HzRGs) with the Canada France Hawaii Telescope Adaptive Optics Bonnette. Along with archival Hubble Space Telescope Wide-Field Planetary Camera data I report on deep imaging in near-infrared (NIR) bands of 6 HzRGs in the redshift range 1 < z < 4. The NIR is probing the restframe visible light - mature stellar populations - at these redshifts. The radio galaxy is resolved in all of these observations and it's `clumpier' appearance at higher redshift leads to the main result - that these galaxies are undergoing mergers at high redshift. Finally, I look to the future of high resolution observations and discuss simulations of imaging and spectroscopy from space. The computer software Next Generation Space Telescope Visible Imager / Multi-Object Spectrograph (NGST VI/MOS) is a `virtual reality' simulator of the NGST observatory providing the user with the opportunity to test real observing campaigns. A web-based version of NGST VI/MOS is available at: http://astrowww.phys.uvic.ca/~steinb.

O-08 Next Generation Space Telescope (NGST)

S. Lilly, University of Toronto

The Canadian Space Agency (CSA) is planning to be a partner with NASA and ESA in the Next Generation Space Telescope (NGST). Canada will make contributions to the project in return for a guaranteed minimum allocation of observing time on the NGST. The NGST is being designed as an 8-m telescope located at the L2 point. There, it will passively cool to about 50K, producing exceptional sensitivity over the 0.6 to 28 micron waveband. NGST's launch is currently scheduled for 2009, with a 5-10 year mission lifetime. I will describe the current specifications for NGST, including the proposed instrument suite. I will also describe the likely Canadian contributions to NGST, presently being negotiated with our partners, and outline how the project will be managed within Canada.

O-09 Recent Developments Regarding Canadian Participation in the Atacama Large Millimeter Array (ALMA)

C. Wilson, McMaster University

I will review recent progress relevant to Canada's participation in the Atacama Large Millimeter Array project. Recent development work in Canada related to ALMA includes: the development of sensitive 230 GHz mixers to be used in testing the prototype antennas at the VLA site; next-generation mixer development; the construction of a 183 GHz radiometer for monitoring the water vapour content above the antennas, which is to be placed on one of the antennas of the Smithsonian Submillimeter Array (SMA) for further tests of this image calibration technique; and the development of a novel design for a water vapour monitor working at a wavelength of 20 microns that has recently received its first tests at the JCMT. I will also summarize recent progress towards a formal agreement for Canada's participation in the ALMA project.

O-10 CASCA President's Address

M. De Robertis, York University

no abstract submitted

O-11 The Potential of White Dwarf Cosmochronology

G. Fontaine, Université de Montréal

White dwarfs represent the end products of stellar evolution for the vast majority of stars and, as such, can be used to constrain the ages of various populations of evolved stars. For example, the oldest white dwarfs in the solar neighborhood (the remnants of the very first generation of intermediate-mass stars in the galactic disk) are still visible, and have been used, in conjunction with cooling theory, to estimate the age of the disk. More recent observations suggest the tantalizing possibility that a population of very old white dwarfs inhabits the galactic halo. Such a population may contribute significantly to "dark" baryonic matter in the Milky Way and may be used to obtain independent estimates of the age of the halo. In addition, white dwarf cosmochronology is likely to play a very significant role in the coming era of giant 8-10 m telescopes when faint white dwarf populations should be routinely discovered and studied in open and globular clusters. When combined with other methods for estimating the ages of these systems, white dwarf cosmochronology should provide unprecedented insight in our global understanding of stellar evolution. This talk will review the potential of the method.

O-12 UV properties of HB stars in GGcs

G. Bono, M. Zoccali, S. Cassisi, and G. Piotto, Rome Observatory

On the basis of HST data we discuss the UV properties of HB stars in selected galactic globular clusters. In order to supply tight constraints on the stellar distribution along the HB the comparison between theory and observations was performed directly in the HST photometric bands. Finally, we mention some useful applications of the color-color plane to estimate both reddening and the location of the gap(s).

O-13 Magnetic Fields of Non-Magnetic Chemically Peculiar Stars

S.L.S Shorlin, G.A. Wade, J.-F. Donati, and J.D. Landstreet, University of Western Ontario

For a century, main sequence A and B stars have been found with strange photospheric chemical abundances. For the last fifty years, some classes of these peculiar stars have been found to have globally ordered magnetic fields, with magnetic peculiar stars comprising 10% of the A and B main sequence population. Other peculiar A and B stars, with different abundance anomalies, have long been considered non-magnetic based on the lack of detectable mean magnetic fields along the line of sight. Recent work has suggested magnetic fields in several examples of these stars, but ones which are very complex as opposed to the well-ordered fields of the magnetic chemically peculiar stars. We present new mean line-of-sight field measurements of 24 "non-magnetic" chemically peculiar stars, which are in some cases an order of magnitude improvement in precision over previous measurements, which confirm their longitudinal fields to be zero. The implications for the strengths and types of fields, if any, which may exist in these stars will be discussed.

O-14 A Search for Eclipsing Binary Stars in NGC 6791 and NGC 6940

M. Blake, York University

The presence of binary stars in old star clusters has bearing on many interesting astrophysical problems - the formation of blue stragglers, SX Phoenicis stars and the dynamical evolution of star clusters. The short period W Uma stars, with periods of around 0.5 days are abundant in some clusters, such as Cr 261, but absent in other clusters; (Kaluzny & Shara 1988). The best way to try to understand the processes that lead to the formation of these systems is to conduct searches for these objects in clusters with a variety of ages and masses. Rucinski & Kaluzny (1993) and Rucinski, Kaluzny and Hilditch (1996) have searched the central regions of NGC 6791 for such systems, detecting 8 contact binaries. We have obtained further observations of NGC 6791 over 6 nights using the Dominion Astrophysical Observatory's Plaskett telescope, and have conducted a search for new binaries and obtained new observations of previously discovered systems. We have also obtained observations of the central region of the nearby, 1Gyr old cluster NGC6940 using the 0.60M telescope of York University on five nights, as part of the undergraduate observing program to York University. We will report on the results of these searches, and outline future observations to search for short period variables in other old clusters.

O-15 Multipolar models of Ap star magnetic fields: Recovery from Stokes IQUV profiles

G.A. Wade, S. Bagnulo and J.D. Landstreet, University of Toronto at Mississauga

We employ new spectropolarimetric observations of Ap star line profiles obtained in all four Stokes parameters (Wade et al. 2000) to recover general dipole plus quadrupole magnetic field configurations (e.g. Landolfi et al. 1998) of two magnetic Ap stars: the cool F0p star Beta CrB and the hotter A4p star 53 Cam. In both cases substantial departures from axisymmetry are detected. While the Stokes IQUV profiles of Beta CrB can be reasonably well fit using our simple model, those of 53 Cam are only very approximately reproduced. We propose that our inability to fit the profiles of 53 Cam points to a field topology which is substantially more complex than has previously been supposed.

O-16 Wind Acceleration in Red Supergiants: What We Know from Binaries

P.D. Bennett, A. Brown, G.M. Harper and W.H. Bauer, University of Colorado

Red supergiants (RSGs) are intermediate and high (4-100 solar) mass stars in their core He-burning phase. The massive supergiants are the progenitors of Type II supernovae. As such, these stars dominate the production of heavy elements and their distribution to the interstellar medium. Most of the mass of these stars is not lost during the supernova explosion but gradually via a massive wind during the star's life as a red supergiant. Unfortunately, the fundamental physical mechanism responsible for driving RSG winds has not been established, and so stellar evolutionary models of RSGs can not presently be computed from first principles without making additional empirical assumptions about the nature of stellar mass loss.

In order to better understand the mass loss process, we have empirically constructed models of the outer atmospheres (chromospheres and winds) of red supergiant primaries in eclipsing binary systems (the zeta Aurigae and VV Cephei stars). The zeta Aur primaries are G-M supergiants, while the less massive companions remain on the main sequence as B-A stars. In the ultraviolet, the cool primaries contribute negligible flux, and the observed spectrum is that of the early-type companion's continuum, with absorption from the supergiant's chromosphere superimposed. Monitoring the chromospheric absorption spectrum near eclipse permits the thermodynamic structure of the chromospheric gas along many lines of sight to be mapped. In this way, an empirical model of the supergiant's chromosphere can be constructed. We illustrate the method using HST/GHRS and ground-based observations of the prototype binary zeta Aurigae.

O-17 HII Region NRAO 655 and its ISM Environment

T. Foster and D. Routledge, University of Alberta

New radio and optical observations of Galactic surroundings near (l,b)= 94,2 (degrees) are presented, revealing new information about the inter- stellar medium and objects in this locale. Of eleven Galactic objects in this area, for example, only two have distance estimates. In this paper, we present new CGPS radio continuum observations of the HII region NRAO 655 (G93.4 + 1.8) at 21cm and 74cm, and optical and radio emission line observations at 656nm and 21cm. The radio spectrum of this object confirms its emission as thermal in origin. From the CGPS HI data we find an atomic hydrogen cavity associated with this object at v = -71.5 km /s. This HI cavity corresponds in position and size to the brightest radio continuum emission from NRAO 655. The corresponding kinematic distance is 8.8 kpc, and NRAO 655's linear size is therefore 70 pc X 130 pc. To confirm the 21cm HI velocity we present the first recombination line detection of NRAO 655 (H158 (alpha) line, v = -72 km/s, width 40 km/s), and the first observations of a molecular cloud interacting with NRAO 655 (at -72 km/s). The first ever optical detection of H(alpha) emission line features is also presented, and the H(alpha) emission line luminosity is determined. We find good correlation between optical and radio morphology and between 60 micron infrared and radio morphology.We find anticorrelation between optical and infrared features of NRAO 655. A physical model for NRAO 655 and its environment is proposed.

O-18 The Chandra Observatory - Overview, Capabilities, Scientific Results, and Status

M. Zombeck, Harvard-Smithsonian CFA

On July 23, 1999 the Chandra X-ray Observatory (CXO) was launched by NASA's Space Shuttle Columbia. The first celestial X-rays were observed on August 12, 1999. Since then, after an initial on-orbit activation and calibration phase, the observing program was initiated. An overview of the Chandra X-ray Observatory will be presented along with its capabilities for high spatial resolution imaging and high resolution spectroscopy. Examples of a variety of initial and recent observations will be presented to highlight the observatory's capabilities and the level of science that can be done. The present status of the observatory and the observing program will be presented.

O-19 Strong Field Gravity with X-ray Observations of Accreting Compact Objects: from the present to the future.

L. Stella, Observatory of Rome

A novel perspective for the detection and study of General Relativistic effects in the strong-field regime has emerged over the last few years from observations at X-ray energies of the innermost regions of accretion flows around compact objects (neutron stars and black holes). The motion of matter in these regions can be probed both through spectroscopic measurements (in particular through the profile of the Fe K-shell lines at ~6.5 keV) and time variability studies (fast quasi-periodic signals originating from matter inhomogeneities). I review the results obtained in this field with the ASCA, BeppoSAX and Rossi XTE satellites and discuss the potential of observations to be carried out with the current generation of X-ray satellites (Chandra and XMM/Newton).

O-20 VLBI Observations of the Core and the Jet in the Center of M81

M. F. Bietenholz, N. Bartel and M. P. Rupen, York University

The nearby galaxy M81 is a grand-design spiral that resembles our own Galaxy in type, size, and mass. M81, like our own Galaxy, contains a nuclear radio source that is most likely associated with a supermassive black hole in the gravitational center of the galaxy. M81's nucleus, however, is virtually unaffected by scatter broadening at most radio frequencies, unlike the nuclear source in our Galaxy, Sgr A*, which is largely hidden behind scattering clouds of gas. M81 is also, at a distance of 3.65 Mpc the nearest spiral galaxy with an AGN. Our observations have shown that its center there is a stationary core and a short, jittery, one-sided jet. We present results from our recent space-VLBI (VSOP) and ground VLBI observations and discuss the implications for our understanding of the center of M81.

O-21 News From The Sudbury Neutrino Observatory

C. Waltham, University of British Columbia

The construction of the Sudbury Neutrino Observatory (SNO) project was started in 1992 and completed in April, 1999. The SNO detector has been in smooth operation since then, collecting a continuous stream of solar and "atmospheric" (cosmic ray-induced) neutrinos. It is sensitive to a supernova event anywhere in our Galaxy. The observatory is a 1,000 tonne heavy water Cherenkov detector situated 2,070 m underground in Inco's Creighton Mine near Sudbury, Ontario. The project is a Canadian, US and UK collaboration. Through the use of heavy water SNO will be able to detect a number of neutrino reactions, including one sensitive specifically to solar electron neutrinos and another to all neutrino types. With these two reactions the detector will be able to search for the neutrino flavour change (a.k.a. "neutrino oscillation") which is widely expected to be the cause of the well-known deficit of measured solar neutrinos.

O-22 Asteroseismology of a Subgiant

D. Guenther, Saint Mary's University

Using the guide telescope on the failed WIRE satellite, Derek Buzasi claims to have observed p-mode (solar-like) oscillations on the subgiant alpha Ursae Majoris A (Buzasi et al. 2000, ApJ). We present the results of a detailed stellar model analysis, pointing out some of the unique features of the oscillation spectra of subgiants. We also discuss whether or not the model results are consistent with the observations.

O-23 MOST Recent News: Progress on Canada's Space Telescope

J.M. Matthews, R. Kuschnig, R. Johnson, J. Pazder, G.A.H. Walker, K. Skaret, E. Shkolnik, and T. Lanting, University of British Columbia

MOST is Canada's first space science microsatellite and its first optical space telescope project, aiming for launch in 2002. It is designed to measure (as its acronym implies) Microvariability & Oscillations of STars in broadband light with a precision of a few micromagnitudes over timescales from minutes to days. The resulting eigenfrequency data will be used primarily for stellar seismology, to probe the structure and ages of Sun-like stars, magnetic stars, Wolf-Rayet stars and metal-poor subdwarfs. The subdwarfs should yield age estimates which would place a meaningful lower limit on the age of the Universe. MOST should also be capable of detecting light variations due to giant extrasolar planets found in Doppler surveys, and constrain their radii and atmospheric compositions.

How will such a Humble Space Telescope (15-cm aperture, on board a 50-kg microsat whose total budget is of order $10M) accomplish all this? The MOST Project has recently completed two Critical Design Reviews so I can answer this question with a brief status report on the mission, the instrument design, and its modes of operation.

O-24 Space weather: the orbital environment of the MOST microsatellite

K. Skaret, and J.M. Matthews, University of British Columbia

Although space provides a dark and atmosphere-free haven for telescopes, the low-earth orbital environment has its own set of observing conditions or 'space weather'. Now, as we enter a period of maximum solar activity, space weather will play an even greater role in the success of space borne astronomy missions. The orbital environment will, in part, determine the sensitivity and duration of the MOST (Microvariability and Oscillations of STars) space telescope mission. In particular, the radiation environment of the low earth polar orbit (800 km altitude) will create cumulative effects in the CCD which may degrade the ability of the satellite to perform the ultra-precise photometry necessary to perform asteroseismology. Ionising dose and bulk damage have been calculated for the satellite shielding geometry and results show that radiation damage of the CCD will not hamper mission goals within the first 2 years of flight. Single event upset (SEU) rates (the occurrence of random bit errors due to a single charged particle) have been calculated. Also, the effects of atomic oxygen on optical coatings and the presence of the bright limb of the earth on photometric precision are discussed.

O-25 Extrasolar Giant Planets: a New Class of Astronomical Objects

T. Guillot, Observatoire de la Côte d'Azur, Nice, France

While Jupiter, Saturn, Uranus and Neptune were the only giant planets known to exist prior 1995, about 9 giant planets out of 10 are now known to lie outside our solar system, a proportion that is increasing steadily. The discovery of planets orbiting solar-type stars has opened up a new field in astronomy, at the crossroads of planetary sciences, stellar physics, studies of protoplanetary disks and celestial dynamics. Our knowledge of these new objects remains fuzzy: we mainly know a minimum value of their mass (0.2 to 10 times the mass of Jupiter) and their orbital characteristics (orbital distances of 0.04 to more than 2AU, excentricities between 0 and 0.6). Yet, this is already sufficient to shake the bases of theories of giant planet formation. A glimpse of the very nature of extrasolar giant planets has now been caught thanks to the discovery of planetary transits in front of the central star every 3.5 days. The slight dimming of the star translates into a planetary radius about 40% larger than that of Jupiter, confirming the expectation that these objects are hydrogen-helium gas giants. Using detail modeling of the structure and evolution of giant planets, we should be able to constrain the amount of heavy elements that they contain, a quantity that should betray their formation mechanisms.

O-26 The D/H Ratio in Giant Planet Atmospheres

G.R. Davis, T.R. Fulton and D.A. Naylor, University of Saskatchewan

The accurate determination of the D/H ratio in the giant planets has profound cosmogonical implications. Until recently, this quantity could be obtained only by indirect methods: by measurement of the CH3D/CH4 ratio using infrared bands of methane, or by measurement of quadrupole lines of HD in the visible region of the spectrum. Both methods result in large uncertainties since their interpretation relies on poorly-determined parameters.

The Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO) offers an unprecedented opportunity to measure the D/H ratios directly, since the first two rotational lines of HD lie in the spectral range of this instrument: R(0) at 112um and R(1) at 56um. Both lines were measured in all four giant planets. Analysis of these data has proved challenging due to a number of instrumental factors. These challenges, their solutions, and the results to date will be presented.

O-27 What MOST Can Tell Us About the Close-in Extrasolar Giant Planets

S. Seager, School of Natural Sciences, Institute for Advanced Study, Princeton, NJ

The discovery of 51 Peg b in 1995, only 0.05 AU from its parent star, heralded an unexpected, new class of planets. The recent transit detection of HD209458b confirms that this class of EGPs --- now with several members --- are gas giants. Five times closer to their parent stars than Mercury is to our Sun, the close-in extrasolar giant planets (CEGPs) are highly irradiated by their parent stars. At effective temperatures of 1100 to 1600 K their atmospheres are closer to those of brown dwarfs and cool L dwarfs than to those of our own Solar System planets. Because of their proximity to the parent star, the CEGPs are potentially bright in reflected light. With high precision photometry, MOST will be able to observe the reflected light curves. For a transiting planet, MOST may be able to detect moons and planetary rings (if they exist) and atmospheric refraction from the CEGP atmosphere. I will present results of theoretical computations, and discuss what can be inferred from the MOST observations.

O-28 A Bayesian Revolution in Spectral Analysis

P. Gregory, University of British Columbia

Fourier power spectral analysis based on the discrete Fourier transform (DFT) is ubiquitous in science as a results of the introduction of the fast Fourier transform by Cooley and Tukey in 1965. In 1987 E. T. Jaynes derived the DFT directly from the principles of Bayesian probability theory and provided surprising new insights into its role in spectral analysis. This was the starting point for an ongoing Bayesian revolution in the subject which I will briefly outline in this paper.

O-29 Modelling Reionization of the Universe

A. Razoumov, University of British Columbia

A numerical scheme for the solution of the three-dimensional, frequency- and time-dependent radiative transfer equation with variable optical depth is developed for modelling the reionization of the Universe. Until now, the main difficulty in simulating the inhomogeneous reionization has been the treatment of cosmological radiative transfer. The proposed approach is drastically different from previous studies, which either resorted to a very simplified, parametric treatment of radiative transfer, or relied on one-dimensional models. The algorithm presented here is based on explicit multidimensional advection of wavefronts at the speed of light, combined with the implicit solution of the local chemical rate equations separately at each point. We have shown that this method is an attractive choice for simulation of astrophysical ionization fronts, particularly when one is interested in covering a wide range of optical depths within a 3D clumpy medium. This scheme is then applied to the calculation of time-dependent, multi-frequency radiative transfer during the epoch of first object formation in the Universe. In a series of models, the 2.5 Mpc (comoving) simulation volume is evolved between the redshifts of z=15 and 10 for different scenarios of star formation and quasar activity. The current numerical resolution is 128^3 (spatial) x 10^2 (angular) x 3 (frequency), and at each point in space we calculate various stages of hydrogen and helium ionization accounting for nine chemical species altogether. These models can be used to predict the observational signatures of the earliest astrophysical objects in the Universe. At present, the calculations are accurate enough to resolve primordial objects to the scale typical of globular clusters, 1e6 solar masses.

O-30 A Global Survey of the Interstellar Medium of the Galaxy

A.R. Taylor, University of Calgary

The Dominion Radio Astrophysical Observatory has just completed a 5-year observing project to image the radio emission from a 70 degree section of the Galactic Plane as part of the Canadian Galactic Plane Survey (CGPS). The DRAO observations provide simultaneous radio continuum images at two wavelengths 74 cm and 21 cm, and spectral line images of the 21-cm line of neutral atomic hydrogen. In the radio continuum at 21 cm, dual polarisation receivers provide sensitive polarimetry of the ISM. These observations form part of an international collaboration to create a data base, within the CGPS region, of arcminute scale resolution, high spatial dynamic range images of all known major components of the Galactic interstellar medium. The CGPS data products have begun to enter the public domain through the Canadian Astronomical Data Centre.

Based on the success of the CGPS, a new global alliance has now been forged to obtain a high resolution 3-D image of the entire Milky Way Galaxy. This project will combine an expanded CGPS in the the north with atomic hydrogen surveys using the Australia Telescope Compact Array in the south, and the Very Large Array in the equatorial region. At the same time, surveys of CO(1-0) will be carried out using the Five Colleges Radio Astronomy Observatory at low longitudes and the Onsala Space Observatory for the northern plane. I will review the scientific highlights of the CGPS and the specifications and science drivers for the expanded CGPS and the Global Milky Way project.

O-31 The Magnetic Field Configuration in the Outer Region of the Galaxy

J.C. Brown and A.R. Taylor, University of Calgary

Several studies have demonstrated that the Galaxy has a magnetic field with an ordered large-scale structure. We do not, however, know how that field is generated, how it is evolving, or what that overall structure is. It is generally believed that the magnetic field follows the basic pattern of the spiral arms of the Galaxy, yet the field's strength and direction between and within the arms is unknown. Different theoretical models of the generation and evolution of the magnetic field predict different directions. Studying the magnetic field and looking for ``reversals'', where the field's direction changes by 180 degrees, will help identify which model is correct. The focus of our research is to use rotation measures from extragalactic point sources in the Canadian Galactic Plane Survey (CGPS), in conjunction with established data from Pulsars to infer information about Galaxy's magnetic field. In particular, we hope to resolve the debate over how many (if any) reversals are present in the outer region of the Galaxy. In our paper, we will discuss the status of our work to address this question and present a comparison between measured rotation measures and those calculated from different magnetic field models of the outer Galaxy.

O-32 Hydrogen Shadows in the Milky Way

S.J. Gibson, A.R. Taylor, C. Brunt, P.E. Dewdney, and L.A. Higgs, University of Calgary

Atomic hydrogen (HI) with T < 100 K represents a considerable fraction of the interstellar matter in our Galaxy. Unfortunately, the spatial distribution of this gas is hard to study directly: in 21cm emission, cold and warm HI are difficult to separate, while 21cm absorption toward continuum sources is limited to small solid angles.

An alternative approach is to observe HI self-absorption (HISA) against warmer and more extensive background HI emission. We present results of the first wide-field synthesis imaging study of HISA being carried out as part of the Canadian Galactic Plane Survey (CGPS), which is mapping Galactic HI over 650 square degrees between longitudes of 74 and 147 at arcminute scales. To date, we have identified a large number of dark and intricate HISA features which display a range of shapes and properties. Surprisingly, the CGPS HISA clouds demonstrate considerable independence from 12CO emission. This suggests either the traditional view of HISA arising from small amounts of HI in molecular clouds is wrong, or the common assumption of CO tracing H_2 requires reexamination.

O-33 Using Molecular Gas Observations to Constrain Models of AGN Fueling in 'Double Barred' Galaxies

G. Petitpas and C. Wilson, McMaster University

High resolution CO maps of galaxies containing near infrared isophote twists (thought to be indicative of a `bar within a bar') show a wide variety of morphologies, despite the fact that the stellar light distributions are very similar. The CO morphologies range from bars, to rings, to miniature spirals. This suggests that there are differences in the molecular gas properties that allow the gas in each galaxy to respond differently to similar galaxy potentials. This talk presents first results of a detailed study of the molecular gas morphology and physical conditions in these `double barred' galaxies. We will show that the molecular gas properties are capable of discriminating between competing models, and that most galaxies do not contain as much molecular gas as the models require to re-produce the observed structures.

O-34 Fe and Dust in the Orion Nebula

P.G. Martin, J.A. Baldwin, G.J. Ferland, P.A.M. van Hoof, D.A. Verner, and E.M. Verner, CITA, University of Toronto

Detailed comparisons are made between numerical simulations of Fe II emission spectra based on a 371 level Fe II atom and recent high resolution and high signal to noise spectra of the Orion Nebula in which forty faint [Fe II] lines are identified. The similar ionization potentials of the parent ions suggest that [Ni II], [Fe II], [N I], and [O I] should all form in the same region and this is confirmed by detailed photoionization models and the finding that lines of these ions all reveal the same velocity (there is an accelerating outflow in the nebular gas with velocity correlated with ionization stage). The dependence of the model [Fe II] spectrum on electron density and pumping by the stellar continuum is investigated. [Fe II] is produced in gas near the ionization front with density about 10^4 cm^-3. Pumping is essential and the important pumping routes responsible for the observed spectrum are identified. Observations in three different ionization stages show that Fe is highly depleted in the plasma (presumably in dust). The presence of silicate dust is revealed by spectral features in the mid infrared at 10 and 20 microns when the dust is warm enough, as it is near the star theta 1 D in the Trapezium. Fe could be locked up in silicates as part of the molecular structure or perhaps in a differentiated core. In the interstellar medium and presumably in the parent OMC 1 molecular cloud there is also carbonaceous dust. The so-called PAH component (or at least the attached H) does not survive in the hot plasma. New models of the mid infrared dust emission are used to investigate whether other carbonaceous dust survives in the nebula.

O-35 Submillimetre Mapping of the HII Region KR 140

C. Kerton, D. Johnstone, D. Ballantyne, and P.G. Martin, DRAO / NRC

We present the results of submillimetre continuum mapping at 450 and 850 microns of the HII region KR 140. KR 140 is a small (5.7 pc diameter), spherically symmetric HII region located in the Perseus arm of the Galaxy at a distance of 2.3 kpc close to, but apparently isolated from, the W3/4/5 star formation complex. Surrounding the HII region are six IRAS point sources (five of which were mapped in this study). Infrared point sources located at the periphery of HII regions are of interest because they may be associated with star formation induced by the expansion of the HII region. Our analysis of the infrared and submillimetre data shows that two of the point sources are embedded late B type stars, two are parts of the dust shell surrounding the HII region, and one is due to emission from an ensemble of smaller sources. At the distance of KR 140, our observations have sufficient to probe down to the large molecular core scale, and we have also detected a number of submillimetre sources not visible in the IRAS data. The three densest clumps are aligned with a ridge seen in CO (J=1-0) emission and we explore whether there could be a causal relationship between the expansion of the HII region and their existence.

O-36 Sub-millimetre Polarimetry of Star Forming Regions in Orion B

G.H. Moriarty-Schieven, B. Matthews, J. Fiege, National Research Council, Joint Astronomy Centre

Polarimetry of sub-millimetre dust emission allows one to trace the structure of magnetic fields perpendicular to the line-of-sight. We present polarimetric images, obtained with the SCUBA polarimeter at the James Clerke Maxwell Telescope, of three star forming regions within the Orion B molecular cloud. NGC2024 contains a string of low- to intermediate-mass protostars embedded within a filamentary ridge, much like beads on a string. Percentage polarization is very small (<2%) toward the ridge, and increases away from the ridge to >5%. The polarization is very ordered as well, with vectors along the ridge mostly parallel to the ridge, while vectors to the east and west of the ridge are oriented roughly +45deg and -45deg respectively with respect to the ridge. We show several synthetic polarization maps based on various magnetic field geometries, in order to constrain the geometry of the ordered magnetic field in this region. NGC2071IR contains a cluster of protostars dominated by a 15 solar mass YSO which drives a massive bipolar outflow. Toward the emission peak the polarization is very weak (<1%), increasing away from the peak. The vector orientations are perpendicular to each other toward the north-east and south-west (i.e. similar to the orientation of the molecular outflow. The third region, LBS23 (HH 24-26) forms a chain of mostly isolated peaks. Here the polarization (and the magnetic field?) is very weak and very disordered. This work is part of the Canadian Consortium for Star Formation Studies.

O-37 Filamentary Molecular Clouds and Their Prolate Cores - Observational Tests from Sub-Millimetre Polarimetry

J.D. Fiege and R.E. Pudritz, CITA

We review our recent model of self-gravitating, pressure truncated, filamentary molecular clouds threaded by helical magnetic fields. By comparing with observational data, we find that many of the observed virial properties of filaments can be explained by our model. We show that our model is in agreement with the observed ~r^{-2} radial density structure of filamentary clouds.

Observations have shown that many of the cores within filaments are probably prolate in shape. We show that such prolate cores can be naturally explained as a consequence of the helical field inherited from the parent filament. We show several examples of our core models and describe the details of their internal structure.

The plane-of-sky component of the magnetic field threading filaments and cores is traced by the sub-millimetre thermal emission from aligned grains. However, it is difficult to interpret polarization maps because the emission may be the result of a complex 3D magnetic structure projected in the plane of the sky. Moreover, the properties and alignment of grains are not completely understood. We show that the polarization can be modeled by making a few simple assumptions regarding the grain properties and their distribution. We show that our filament models are in qualitative agreement with some recent polarimetric maps obtained by SCUBA. Future tests of our models will rely heavily on this type of analysis.

O-38 Star Formation in NGC 6334 I and I(N)

W. H. McCutcheon, G. Sandell, H.E. Matthews, T.B.H. Kuiper, E.C. Sutton, W.C. Danchi and T. Sato, University of British Columbia

The northern section of the molecular cloud complex NGC 6334 has been mapped in the CO and CS spectral line emission and in continuum emission at a wavelength of 1300 microns. Our observations highlight the two dominant sources, I and I(N), and a host of weaker sources. NGC 6334 I is associated with a cometary ultra-compact HII region and a hot, compact core <10" in size. Mid-IR and CH3OH observations indicate that it is also associated with at least two protostellar sources, each of which may drive a molecular outflow. Region I has an extremely high velocity outflow and with a mechanical luminosity of 390 L(sun). A dynamical age for the outflow is about 3000 years. We also find a weaker outflow originating from the vicinity of NGC 6334 I. In CO and CS this outflow is quite prominent to the NW, but much less so on the eastern side of I, where there is very little molecular gas. Spectral survey data show a molecular environment at position I which is rich in methanol, methyl formate, and dimethyl ether, with lines ranging in energy up to 900 K above the ground state. NGC 6334 I(N) is more dense than I, but cooler, and has none of the high excitation lines observed toward I. I(N) also has an associated outflow, but it is less energetic than the outflow from I. The fully sampled continuum map shows a network of filaments, voids, and cores, many of which are likely to be sites of star formation. A striking feature is a narrow, linear ridge that defines the western boundary. It is unclear if there is a connection between this filament and the many potential sites of star formation, or if the filament existed prior to the star formation activity.

O-39 Resolving and Recognizing the Far Infra-red Background: SCUBA Photometry of Known Galaxies.

M. Halpern, C. Borys, S. Chapman, A. Sajina, and D. Scott, Department of Physics and Astronomy, UBC

Unlike the cosmic microwave background, the far infrared background can be resolved into individual sources, which are distant dusty galaxies. Studying their distribution reveals a lot about the cosmic star formation rate history. These sources routinely show up as several mJ detections in deep SCUBA images. However the beam size is large (14") and galaxies at many different redshifts have the same apparent brightness so identification is difficult.

This is a progress report on an effort to study the star formation rate history while avoiding these source identification difficulties. We perform photometry with SCUBA on pre-selected lists of galaxies in order to determine the contribution to the far infrared background of the populations from which the lists were drawn. This statistical technique allows us to make measurements below the individual source confusion limit. We have looked at a collection of z=3 Lyman-break galaxies, which do not contribute to the background, and at a set of ISO-selected galaxies from the FIRBACK N1 field, which do.

O-40 The Brighter Side of Sub-mm Source Counts: a SCUBA Scan-map of the Hubble Deep Field

C. Borys, S. Chapman, M. Halpern and D. Scott, University of British Columbia

We present here maps of a 12x12 arcminute region centred on the Hubble Deep Field taken with the 450/850 micron SCUBA camera on the JCMT. The maps have an average one-sigma sensitivity to pointsources of roughly 90/6 mJy at 450/850 micron respectively, and thus probe the brighter end of sub-mm source counts. Given the observational challenges associated with SCUBA, an outline of the careful data analysis required by the dataset will be given first. The discussion will then focus on the implication that sources in the map have on current fits, which have been based on deeper, yet smaller area surveys, to the sub-mm number counts. The talk will end with a short description of observation and data analysis followup work currently in progress.

O-41 A Poor Man's Alternative to Numerical Simulations

J. E. Taylor and A. Babul, University of Victoria

Observations of the Milky Way and the Local Group are providing increasingly stringent tests of theories of galaxy formation. Simulating galaxy formation numerically is a difficult task, however, and computationally very expensive. To avoid this computational expense, we have developed a semi-analytic model of the dynamical aspects of galaxy formation. I will describe the main features of this model, and compare its predictions to results from high-resolution numerical simulations. The model succeeds in reproducing many of these results, from the distribution of substructure present in galactic halos to the evolution of individual satellite galaxies in the halo of the Milky Way, at a fraction of the computational cost. As such it has potential applications in studying the survival of the Milky Way's disk, the structure of its dark halo and the formation of its stellar halo.

O-42 BOOMERANG Measurements of CMB Anisotropy

B. Netterfield, University of Toronto

Since the discovery of the Cosmic Microwave Background (CMB) in the 1960's, it has been recognized that measurements of spatial structure in the CMB would significantly increase our understanding of the Universe. Images of acoustic oscillations in the primordial plasma are frozen in at recombination, when the ionized plasma cools to a neutral gas. The angular spectra of these fluctuations can be used to limit the value of cosmological parameters, such as the total energy density of the Universe, and the physical density in Baryons. A generation of experiments around the world has begun the process of characterizing these fluctuations.

A significant step forward in this process is BOOMERANG, a Long Duration Balloon Borne telescope, which made its first antarctic flight in Dec 1998 - Jan 1999. This flight has produced images of the CMB with sensitivity and resolution adequate to resolve these fluctuations, and to capitalize on the CMB's cosmological potential. These images, and their associated angular power spectra will be presented, along with cosmological implications.

P-01 The Spectral and Photometric Imaging Receiver (SPIRE)

G.R. Davis and D.A. Naylor, University of Saskatchewan

The Far Infrared and Submillimetre Telescope (FIRST) is an ESA mission for launch in 2007. It will carry a low-emissivity, 3.5-m telescope and will operate at the Sun-Earth L2 point for 4.5 years, providing a large amount of observing time at wavelengths unrestricted by the terrestrial atmosphere. The entire payload will be cooled with an on-board supply of liquid helium, which determines the lifetime. The JSSA and the CSA recently aapproved Canadian participation in SPIRE, one of the three instruments on the FIRST payload. The main scientific goals of SPIRE are deep extragalactic and galactic imaging surveys and spectroscopy of star-forming regions in our own and nearby galaxies. The SPIRE instrument comprises a 3-band imaging photometer covering the spectral range 200-500um, and an imaging Fourier transform spectrometer (FTS) covering the range 200-670um. The FTS employs a dual-beam configuration with novel broad-band intensity beam dividers. The SPIRE detectors are feedhorn-coupled NTD spider-web bolometers.

The Canadian contributions to the SPIRE instrument will be (a) a cryogenic shutter to provide a cold, controlled background to the instrument, and (b) manpower for the Instrument Control Centre. In addition, we are developing an imaging FTS to the SPIRE design for use in ground-based extragalactic observations with the JCMT. The SPIRE project, the opportunities for Canadian participation, and the ground-based FTS will be described.

P-02 FIRST/HIFI

M. Fich, University of Waterloo

The Far InfraRed and Submillimeter Telescope (FIRST) will be an facility-class space observatory operating at wavelengths between 60 and 670 microns. It will be launched, with the Planck satellite, in 2007 to the second Lagrangian point with a minimum lifetime of three years. The FIRST telescope is 3.5 m in diameter and passively cooled to 80K.

HIFI is a high resolution heterodyne spectrometer is one of three focal plane science instruments for FIRST. The primary purpose of FIRST is to study astrochemistry and HIFI is the main instrument for studying atomic and molecular spectral lines. A consortium of approximately 20 Canadian astronomers are planning to contribute a central part of the HIFI instrument and, in return, will be part of the HIFI Science Team. This poster presents details of the science to be carried out with HIFI and will describe how interested Canadian scientists can become involved in the mission.

P-04 BLAST, a Balloon-borne Large Aperture Sub-millimetre Telescope

M. Halpern, B. Netterfield, D. Scott, P. Ade, J. Bock, P. Debernardis, M. Devlin, J. Gunderson, D. Hughes, J. Klein, S. Masi, P. Mauskopf, L. Page and G. Tucker, University of British Columbia

We are building BLAST, a Balloon-Borne Large Aperture Submillimetre Telescope. The design incorporates a 2 to 3 m aperture mirror and large format bolometer arrays operating at 250 and 500 microns and will operate from a long duration balloon platform. BLAST will address some of the most important galactic and cosmological questions regarding the formation and evolution of stars, galaxies and clusters. It will conduct large area, sensitive galactic and extra-galactic surveys which will (i) identify large numbers of distant high redshit galaxies; (ii) measure cold pre-stellar sources associated with the earliest stages of star and planet formation; and (iii) make high resolution maps of diffuse galactic emission from low to high galactic latitudes. A first flight is expected in 2002.

P-05 Status Report and Upcoming Developments of Gemini

S. Côté, D. Crabtree and T. Davidge, The Canadian Gemini Office

We will review the state of the Gemini telescopes, as the Mauna Kea telescope is preparing for operations and the Cerro Pachon one for first light in the coming few months. We will also report on the first canadian call for proposals for the shared-risk Quickstart semester. Finally we will present the instruments to be offered in the coming semester.

P-06 Twenty Years of CFHT Publications

D.R. Crabtree and L. Bryson, NRC/HIA

The first scientific paper published using CFHT data was submitted in May 1980 and published in August of that year (1980, PASP, 92, 409). In the following 20 years CFHT established itself as one of the leading research telescopes in the world. A database of all refereed CFHT publications is maintained by Liz Bryson, librarian, in collaboration with former CFHT Senior Resident Astronomer, Dennis Crabtree. We have augmented this database with citation numbers retrieved using the ADS (Astrophysics Data System). We present an analysis of the CFHT publication and citation data in this poster.

P-07 Wide-Field Survey of the Globular Cluster System of M104

M. VanDalfsen, J.J. Kavelaars, W.E. Harris, D. Hanes and G. Harris, McMaster University

Last year we acquired deep, wide-field images of the Sombrero galaxy (M104) using the CFH12k camera on the Canada France Hawaii Telescope. M104 is a large edge-on disk galaxy at a distance of 10 Mpc, and has a relatively large number of globular clusters. From this data we will be able to study M104's globular cluster population in great detail. We will present some initial results of the GCS such as the globular cluster luminosity function, colour distribution in (B-R) and thus metallicity, and radial profile.

P-08 The Metal-rich Globular Cluster NGC 6553: Observations with WFPC2, STIS, and NICMOS.

S.F. Beaulieu, G. Gilmore, R.A.W. Elson, R.A. Jonhson, B. Santiago, S. Sigurdsson, and N. Tanvir, University of Cambridge

We present a HST study of the metal-rich globular cluster NGC 6553 using WFPC2, NICMOS and STIS. Our primary motivation is to calibrate the STIS broad-band LP magnitude, and the NICMOS J_110 and H_160 magnitudes, against standard V and I magnitudes for stars of known metallicity and absolute (V) magnitude, for application to our study of LMC globular clusters. NGC 6553 has been shown in earlier studies to have a very unusual colour-magnitude diagram, so we also use our data to investigate the reddening, distance, luminosity function and structure of this cluster. The horizontal branch of NGC 6553 in (V,V-I) is tilted at an angle close to that of the reddening vector. We show that extinction does not, however, explain the tilt, which is presumably a metallicity effect. The colour-magnitude diagram shows an apparent second turnoff some 1.5 magnitudes fainter than that of the cluster. We show that this is most likely the background Galactic bulge: however, in that case, the colour-magnitude diagram of NGC 6553 is not a good match to that of the field bulge population.

P-09 The CFHT Open Star Cluster Survey : CCD Photometry of NGC 2099

J. S. Kalirai, H.B. Richer, P.R. Durrell, G.G. Fahlman, G. Marconi and F. D'Antona, University of British Columbia

We will present preliminary CCD photometric results for the open star cluster NGC 2099 (M37). NGC 2099 is the first of 19 carefully selected open clusters in a survey which was taken using the CFH12k CCD camera. This is the largest close-packed CCD currently being used for astronomical research. The goals of this survey are to identify a large collection of white dwarf stars (approximately 100) and to produce the first major observational tests for the theoretical models available for the white dwarf initial-final mass relationship. The colour-magnitude diagram of NGC 2099 shows that it contains a very rich stellar population and one of the longest (10 magnitudes) and most tightly constrained main sequences ever established for open star clusters. The CMD is also deep enough (V=24) to reveal about a half dozen white dwarf candidates. Additionally, there is an excellent agreement between the theoretical isochrones and the data for the main sequence of the cluster. Consequently, our derivations of cluster parameters, such as age and distance, have refined previous values significantly.

P-10 BD+61 2213: an Early-Type Binary System in the Open Cluster NGC 7160

D.E. Holmgren and A.E. Tarasov, Brandon University

New spectral data and orbital parameters are presented for the short- period (P=1.2d) B3 binary system BD+61 2213. This star is a member of the open cluster NGC 7160. On the basis of a spectroscopic orbit and component line profiles (He I 6678A and H alpha) recovered from a spectral disentangling solution, we find primary and secondary minimum masses of 4.3 and 3.2 solar masses respectively. As the system is known to be non-eclipsing, we find a maximum orbital inclination of 53 degrees, which implies that the masses must be at least 8.5 (primary) and 6.2 (secondary) solar masses. From measures of the equivalent width of the component He I 6678A profiles and comparisons of these data with non-LTE model atmosphere calculations, we conclude that both stars are slightly evolved.

P-11 W UMa-type Binary Stars in Globular Clusters

S.M. Rucinski, University of Toronto

A sample of 86 contact binary systems in 14 globular clusters with available color index data in (B-V) or in (V-I) has been analyzed. A large fraction of all systems (at least one third) are numerous foreground Galactic Disk projections over long lines of sight to the clusters. Since the selection of the cluster members has been based on the MV(logP,color) calibrations, the matter of a metallicity-correction required particular attention with the result that such a correction is apparently not needed at the present level of accuracy. Analysis of the color-magnitude and period-color relations shows that globular cluster members have different properties from the Galactic Disk contact systems: They are under-luminous mainly because of the smaller sizes and, consequently, have shorter orbital periods; the color-index effect of the diminished blanketing is relatively less important, especially for (V-I). Because of the indications of a bias against discovery of small-amplitude systems below the Turn Off Point (TOP), efforts at determination of the frequency of occurrence of the contact systems below the TOP have been judged to be premature. However, the frequency among the Blue Straggler stars could be moderately well established at about 45+/-10 BS stars per one contact BS binary; thus, contact binaries are about 3 times more common among the BS stars than among the Old Disk population dwarfs. Contact binary systems with periods longer than 0.6 days are absent in the sample, possibly because the more massive stars have left the contact binary domain.

P-12 Disk Galaxies Within Cold Dark Matter Halos

A. Font and J. Navarro, University of Victoria

We use numerical simulations to investigate the secular evolution of galaxy disks formed within realistic cold dark matter halos. In particular, we explore the effects that substructure and satellite accretions may have on the long-term stability of stellar disks, in an attempt to derive quantitative constraints on the nature of halo substructure and on the rate of satellite accretions experienced by a typical spiral disk. These constraints are then compared with N-body simulations in order to assess whether the evolving potential wells of cold dark matter halos are acceptable hosts of observed galaxy disks.

P-13 HST Archive Imaging Study of Four cD Galaxies

W. Okon and W. Harris, McMaster University

We have extracted deep I-band imaging of central cD galaxies from Abell 262, 3560, 3565, 3742. These are used to study luminosity profiles of the galaxies (three were found to have central region dust lanes and peculiar features which indicate past histories of mergers or interactions). All four have globular cluster systems for which we will obtain luminosity functions down to the GCLF turnover point. The original data were discussed in Lauer et al. (1998).

P-14 The Nature of the Halo Population of NGC 5128 Resolved with NICMOS

F.R. Marleau, J.R. Graham, S. Charlot and M.C. Liu, University of Cambridge

We present the first infrared (IR) color-magnitude diagram (CMD) for the halo of a giant elliptical galaxy. The CMD for the stars in the halo of NGC 5128 (Centaurus A) was constructed from HST NICMOS observations of the WFPC2 CHIP-3 field of Soria et al. (1996) to a 50% completeness magnitude limit of [F160W]=23.8. This field is located at a distance of 08'50" (~9kpc) south of the center of the galaxy. The luminosity function (LF) shows a marked discontinuity at [F160W]~20.0. This is 1-2mag above the tip of the red giant branch (TRGB) expected for an old population (~12 Gyr) at the distance modulus of NGC 5128. We propose that the majority of stars above the TRGB have intermediate ages (~2 Gyr), in agreement with the WFPC2 observations of Soria etal. (1996). Five stars with magnitudes brighter than the LF discontinuity are most probably due to Galactic contamination. The weighted average of the mean giant branch color above our 50% completeness limit is [F110W]-[F160W]=1.22+/-0.08 with a dispersion of 0.19 mag. From our artificial-star experiments we determine that the spread in color is real, suggesting a real spread in metallicity. We estimate the lower and upper bounds of the stellar metallicity range by comparisons with observations of Galactic star clusters and theoretical isochrones. We find that, in the halo field of NGC 5128 we surveyed, stars have metallicities ranging from roughly 1% of solar at the blue end of the color spread to roughly solar at the red end.

P-15 Photometry of the Outer Halo of M31

P.R. Durrell, W.E. Harris, C.J. Pritchet and T. Davidge, University of British Columbia

We are presenting results from a wide-field CFHT-UH8K photometric study of the stars in the outer halo (r=20-45 kpc) of M31. Data reduction is complete for the first field, which is located 20 kpc from the centre of M31 along the SE minor axis, and the resulting VI colour-magnitude diagram reaches I=23.5, which is 3 magnitudes below the RGB-tip. The metallicity distribution function (MDF) of this field is derived using observed globular cluster RGB sequences, and shows the dominant high-metallicity ([Fe/H]=-0.6; much larger than in the Milky Way halo) population previously observed in more interior fields. In addition, a significant (30-35%) metal-poor component has been detected. The stellar surface density in this field continues to follow the steep decline observed for the inner halo. We will also comment on other goals of our survey.

P-16 The Interstellar Medium of M32

G. Welch and L. Sage, Saint Mary's University

The elliptical galaxy M32 is one of several small satellites of the giant spiral M31, first-ranked member of the Local Group. We have used the VLA to search for atomic hydrogen in M32, thereby complementing our earlier attempt to detect molecular gas in this galaxy. Wispy foreground emission, primarily near -33 and -50 km/s, extends across the primary beam. Curiously, a relatively compact, isolated feature at -74 km/s lies on top of the optical image of M32. Given the latitude of -22 degrees this is likely to be a small, nearby HI cloud. No emission is seen near the -205 km/s optical velocity of M32. We find that this galaxy contains less than 40,000 solar masses of cool gas inside an area comparable to that which in similar Local Group members harbours nearly one million solar masses of gas. We show that this poses a fundamental puzzle for understanding the evolution of small elliptical galaxies.

P-17 Diffuse Molecular Gas in the Milky Way

K.A. Douglas, A.R. Taylor, University of Calgary

Observations of the gas and dust content of high-latitude gas clouds have shown interesting relationships between the emission by various constituents of these structures. Several studies comparing IRAS, HI and CO emission in these cirrus clouds have yielded evidence of a molecular component which is not traced by the emission of CO molecules (Reach et al. 1994 ApJ 429, 672; Meyerdierks & Heithausen 1996 A&A 313, 929; Boulanger et al. 1998 A&A 332, 273). Infrared excess emission from IRAS data points to the possibilty of molecular gas component that is warmer and more diffuse than the component of molecular gas traceable by CO. In these studies, the "diffuse" component of molecular hydrogen is found to be comparable in mass to the HI content. This diffuse gas may be widely abundant in the plane of the Galaxy. If present, on the same scales as in these high latitude clouds, it has important implications for many areas of astrophysical interest.

The Canadian Galactic Plane Survey (CGPS) offers an excellent opportunity to study the phenomenon of diffuse molecular gas in the plane of the Galaxy by combined analysis of pc-scale resolution images of CO, HI and dust emission over a large area of the Galactic disk. Preliminary searches in some CGPS fields have already suggested the presence of molecular gas in regions where CO emission is not found. I will present some results of these initial searches and comment on the methodology that will be used to trace and quantify the properties of this diffuse molecular component of the interstellar medium.

P-18 On The Power-Law Relation between The Scalar Field and The Cosmic Expansion Factor in Scalar-Tensor Theories

S.O. Mendes, M.N. Butler, and M.J. West, Saint Mary's University

We explore cosmological solutions to a general scalar-tensor theory for gravity. It is shown that a power-law relationship between the scale factor and the scalar field might be obtained in order to recover the Brans-Dicke expression for the effective gravitational constant. Furthermore, the exponent of such power-law relation is shown to constrain the coupling function Omega of the theory.

P-20 A Search for Protostellar Collapse in Late Class I Sources

E.M. Gregersen, D. Mardones, N.J. Evans II, P.C. Myers, Y. Shirley and C. Wilson, McMaster University

Asymmetric spectra of optically thick spectral lines are associated with protostellar collapse in young stellar objects. Such asymmetries have been believed to be confined solely to the Class 0 stage, but collapse signatures have now been observed in Class I sources with T_bol < 200 K. We present partial results of a survey that extends earlier results in Class 0 and I sources of HCO+, a molecule that shows strong line asymmetry in simulations of collapsing clouds, to Class I sources with T_bol < 650 K to find when protostellar collapse ends and how infall motions change with time.

P-21 Activity Related to Star Formation Associated with G79.3+0.3

R.O. Redman, D.D. Balam, P.A. Feldman and S.J. Carey, HIA / NRC

We have employed several telescopes in a multiwavelength study of star forming activity in and around the nearby Infrared-Dark Cloud (IRDC) G79.3+0.3. The Midcourse Space Experiment (MSX) provided images of the region at 8 microns. The JCMT was employed with SCUBA to image the region at 850 and 450 microns, and with RxA3 to map the transitions of 13CO (2-1) and C18O (2-1). The NRC's 1.82 m Plaskett Telescope was used to image the region with various optical and IR filters, including the transitions of H_alpha, [S II] at 6716/6731 A, [Fe II] at 1.64 microns, the S(1) line of H2 (v=1-0) at 2.12 microns, and a narrow-band CO filter at 2.30 microns.

The SCUBA images reveal a variety of objects in the early stages of star formation, including a Class-0 protostar and another protostar showing evidence of infalling gas. All of the bright, compact sources in the SCUBA images have line wings indicative of outflow. Magnetic fields inferred from the polarization images appear well-ordered and aligned with structures in the maps of dust and gas.

The images made with the Plaskett Telescope have revealed the presence of one or two Herbig-Haro (HH) jets. The source of the strongest jet appears to be a T Tauri-like star embedded in an edge-on disk.

P-22 Interstellar Clumps: Physical Relations, Magnetism, and Energy.

J.P. Vallée, HIA / NRC

Universal scaling relations exist in interstellar molecular clouds and clumps, governing the mean physical parameters such as the gas density n, diameter D, magnetic field B, and gas linewidth W (for recent reviews, see Vallée, 1997 and 1998). The relations follow the form: <n> ~ D**c, <B> ~ <n>**k, <B> ~ <D>**p, <W> ~ <D>**q. In molecular clouds, with D >1 pc but <100 pc, the exponents are: c= -1.0; k = +0.5; p= -0.5; and q = +0.5 (e.g., Larson, 1981). There is a natural separation between clouds and clumps, occurring near 0.5 pc. One does not expect the physical behaviors of clumps (<0.5 pc) to be the same as for clouds (>1 pc). In cold clumps, with D >0.01 pc but <0.50 pc, the gas density is higher than in clouds. Clumps are beginning to reveal their secrets, using observed findings at high angular resolution. Here I report on a statistical study of the exponent values c, k, p, q for clumps, and on the energy components for clumps. The exponent values for clumps are found to differ from those found by Larson (1981) for molecular clouds. The differences could be indicative of ongoing accretion processes in shocked media. The energy distribution in clumps reveals that the support against gravitational collapse in clumps with sizes >0.1 pc comes mainly from turbulent energy, while clumps with sizes <0.1 pc are supported by both magnetic and turbulent energies. The clump size of 0.1 pc is critical in many other aspects.

P-23 Star Formation and Magnetic Field Structure along the OMC-3 Ridge in Orion A

B. Matthews and C. Wilson, McMaster University

OMC-3 is part of the so-called Integral Filament in the Orion A molecular cloud. Located at its northern tip, this ridge contains nine embedded dust condensations. Data from the Owens Valley interferometer support previous work which reveals that two of the condensations do not yet show evidence of collapse. The SCUBA polarimeter at the James Clerk Maxwell telescope has been used to measure polarization from aligned dust grains at 850 microns along the 6 arcminute ridge. The polarization patterns reveal the net plane-of-sky magnetic field orientations. A recently developed model of filamentary clouds utilizes helical magnetic fields to support and shape the filament. This model predicts polarization patterns like that observed in OMC-3. Additionally, the depolarization (decreased polarization percentage) along the bright spine of the ridge is predicted by the helical field model and is observed both toward the dust condensations and toward the filament alone. This provides evidence that the features seen in JCMT maps are likely dominated by the filament, not the individual condensations.

P-24 Dust in Very Young Star Forming Regions

S. Plante, Université Laval

Dust is strongly affecting the light we receive from stars. Its effect is most striking when one is looking at very young massive star forming site. As dust affects mostly the UV light and because massive stars are mostly emitting in this spectral range, its imperative to understand how dust is distributed and how the physical parameters of the star forming region affects the dust constituents and distribution. We looked at three different star forming regions in the near and mid-infrared to examine the distribution of the small aromatic molecules as well as the star distribution. We evaluate that the small aromatic molecules emitting in the mid-infrared are probably absent in the regions closest to the ionizing stars, but that they are present where only diffuse radiation is present.

P-25 Integral Field Spectroscopy of Evaporating Disk Systems in Orion using OASIS at CFHT

D. Johnstone, G. Mallen-Ornelas and J. Bally, University of Toronto

We present preliminary results on the structure of objects within the Orion Nebula obtained from two-dimensional spectroscopic observations taken at CFHT. Using OASIS, an Integral Field Spectrograph coupled to the Adaptive Optics Bonnette we have mapped several emission lines and their characteristics, from a sample of young stellar environments at sub-arcsecond spatial resolution. When analysis is complete, the survey will yield information about a variety of atomic ions, probing the physical conditions within the multilayered environment - PDR, neutral flow, shock layers, and ionized gas - of the evaporating disk systems.

P-26 Stellar bubbles and shells in Cygnus

S. Pineault, E.M. Arnal, C.E. Cappa, S. Cichowolski, M. Normandeau and N. St-Louis, Université Laval and NRC.

Data from the Canadian Galactic Plane Survey (CGPS) and from the HIRES infrared survey (IRAS) are used to determine the morphology and physical properties of the interstellar medium in a two-degree by two-degree region in Cygnus. A new and highly symmetrical infrared shell is identified, seen partially overlapping the supernova remnant G78.2+2.1. A compact source is clearly visible near the geometrical center of the shell both in the infrared and in the radio continuum at 4.85 GHz.

P-27 The Canadian Galactic Plane Survey: Exploring the Interstellar Medium using Radio Polarimetry

T. Landecker, P.E. Dewdney, A.D. Gray, B. Uyaniker, J.C. Brown, A.R. Taylor and M. Peracaula, DRAO / NRC

(Abstract not available at press time)

P-28 The Canadian Galactic Plane Survey: The Galactic Plane Seen In Radio Continuum

R. Kothes, B. Uyaniker and T. Landecker, DRAO / NRC

We present images from the Canadian Galactic Plane Survey in radio continuum between 75 and 100 degrees of Galactic longitude and -4 and +6 degrees of Galactic latitude. These observations were taken at 408 MHz and 1420 MHz with the DRAO Synthesis Telescope. Missing short spacings were taken from the 408 MHz all-sky survey by Haslam and the 1420 MHz Stockert Survey of the Northern Hemisphere. We compare the radio continuum observations with the IRAS 60 Micron all sky survey to outline different structures and emission mechanisms in this part of our Galaxy.

P-29 Variable Analysis of Compact sources in the Canadian Galactic Plane Survey

S. Wilder, A.R. Taylor and L.A. Higgs, University of Calgary

The 1420 MHz radio continuum images from Canadian Galactic Plane Survey contain tens of thousands of compact radio sources in the plane of the Galaxy down to a flux density limit of about 1 mJy. Some fraction of these sources will be exotic Galactic radio emitters such as energetic binary star systems, pulsars, flare stars that can be identified by variable radio flux. We are carrying out a sensitive search for variable radio sources bycombined analysis of the CGPS radio images and the Northern VLA Sky Survey, which has a similar radio continuum sensitivity and resolution to the CGPS. This variability search is an order of magnitude deeper than any previous survey for variable radio sources in the Galaxy. We present initial results of an analysis of about 5000 sources in an 80 square degree subregion of the CGPS. The nature of the population of radio continuum sources is further investigated by measurement of spectral indices by comparison with the Westerbork Northern Sky Survey images at 327 MHz.

P-30 ISO Observations of Proto-Planetary Nebulae

K. Volk, S. Kwok and B. Hrivnak, University of Calgary

Objects evolving from the asymptotic giant branch (AGB) phase to the planetary nebula (PN) phase have strong infrared emission from their remnant circumstellar dust shells. It was by searching for objects with infrared properties intermediate between those of AGB stars and PNs that most protoplanetary nebulae (PPN) have been identified. We obtained infrared spectra of a number of PPN during the ISO mission which are now being analyzed. The carbon-rich sources, which were highly obscured carbon stars on the AGB, show a number of interesting infrared features such as the UIR bands (due to small carbon-based molecules), the 21 micron feature (which may be due to TiC grains), and the 30 micron feature (unidentified). Detailed analysis of the infrared spectra show that the underlying infrared emission is very well fit by amorphous carbon grains, and this allows us to study the features explicitly. We have strong evidence that the 30 micron feature is made up of two components: a feature at 27 microns and a broader feature at 34 microns. These components vary in strength from source to source, and currently we do not know how all the features are related. The changes in these features in different PPNs indicate chemical evolution of the circumstellar material, which may include the formation of "organic" compounds. We will present the results of detailed dust emission models of these objects.

P-31 The First Year of FUSE (Far Ultraviolet Spectroscopic Explorer).

J.B. Hutchings, A.W. Fullerton and P. Chayer, NRC and the Canadian Space agency

The Far Ultraviolet Spectroscopic Explorer (FUSE) was successfully launched into orbit on June 24, 1999. Its mission is to explore the universe at far-ultraviolet wavelengths (905--1187 Angstroms) with high spectral resolution. Thus far, over 200 galactic and extragalactic targets drawn from Science Team and Guest Investigator programs have been observed. Highlights of the early results include 1) detection of hot gas in the Galactic halo and extragalactic sources via the O VI 1032-8 A lines; 2) widespread presence of cool molecular Hydrogen seen in the strong Lyman and Werner bands; 3) abundance studies in the interstellar medium of our and other galaxies; 4) differences in the structure of winds of massive stars in the LMC and SMC. A primary objective of the FUSE mission is the determination of the abundance ratio of deuterium to hydrogen along many sight lines. FUSE performance and science results are described, along with opportunities for Canadian observing time in cycle 2.

P-32 FUSE Observations of the Subdwarf B Star PG0749+658

P. Chayer, R.G. Ohl and H.W. Moos, Johns Hopkins University

High-dispersion observations of the far-ultraviolet (FUV) spectrum of the subdwarf B star PG0749+658 (Teff = 24,600K and log g = 5.5) reveal the presence of many photospheric and interstellar lines. The spectrum, obtained by the Far Ultraviolet Spectroscopic Explorer (FUSE), has a resolution of about R = 12000--15000 and covers a wavelength range of 905--1187 Angstroms. We determine C, N, Si, P, S, Cr, Mn, Fe, and Ni abundances, and upper limits on the abundance of Cl and V, using a grid of synthetic spectra based on a LTE stellar atmosphere model. Abundance anomalies are observed in the atmosphere of this sdB star. He, C, N, Si, and Cl are depleted by a factor greater than 10 with respect to solar, while P, S, and Fe are diminished by less than a factor of 10. We measure a solar abundance of Cr and Mn and a Ni enhancement of about 0.6 dex. The measured abundances are generally consistent with predictions based on the equilibrium radiative levitation theory, except for He and Si. The underabundances of He and Si are not explained by this theory alone.

P-33 A FUSE Survey of O VI in the Winds of LMC O Stars

A.W. Fullerton, D.L. Massa, and J.B. Hutchings, University of Victoria/Johns Hopkins University

High-resolution FUSE spectra of stellar wind profiles in the O VI resonance doublet are presented for a sample of O stars in the Large Magellanic Cloud. This transition is the best diagnostic of high-energy processes in the optical/UV range. It is present in the winds of all the stars in the sample, which cover spectral classes from O3 to B0.5 with emphasis on luminosity classes I-III. The strength and morphology of the P Cygni profiles change systematically along the temperature sequence: early types exhibit pronounced emission lobes, while later types show weaker emission but comparatively strong absorption at high velocity. This morphology suggests that the distribution of O VI ions is concentrated towards larger wind velocities, particularly for the later spectral types. Work is underway to quantify this distribution, in order to constrain the properties of the ensembles of embedded shocks that are the likely production mechanism for O VI.

P-34 A Far-UV Spectral Library of Hot Stars with FUSE

A. Pellerin, Université Laval

During my Ph.D., I will build an evolutionary synthesis code with applications for far-UV spectroscopy. With the launch of the Far Ultraviolet Spectroscopic Explorer (FUSE), the far-UV spectral range, which is very rich of information of all kind, is now opened to us. Among others, young regions of star formation display, in the far-UV, P-Cygni profiles which are formed in hot star winds. I will present here a sketch of the spectral library of hotstars that I am building based on FUSE data. This library contains so far about 30 spectra of OB stars essentially from the Small Magellanic Cloud. These data already show line behaviors which depend on the hot star physical parameters. One application of the synthesis code, will be, for example, to study the young stellar populations in relation with the starburst-AGN connection.

P-35 The Interstellar Environment of the Wolf-Rayet star WR130

S. Cichowolski, E.M. Arnal, S. Pineault and J.C. Testori, Instituto Argentino de Radioastronomia

The environment of WR130 has been studied using the 21cm HI line and radio continuum (408 and 1420 MHz) data obtained with the DRAO Synthesis Telescope and the HIRES data from the IRAS survey. Both in the radio continuum and in the IRAS data, a large scale ring shape structure is seen. From the analysis of the HI distribution, an HI bubble is found in the velocity range from about -10 to 0 km/s. However the WR star is not in the center of the ring, but it lies in its border. There is also a known HII region superposed on the ring. The most striking characteristic of this HI cavity is its good correlation with the continuum stucture mentioned above. The spectral index distribution is determined using the radio continuum data.

P-36 VLBI Imaging of the Gravity Probe B Guide Star HR 8703

R. R. Ransom, N. Bartel, M. F. Bietenholz, D. E. Lebach, M. I. Ratner, I. I. Shapiro and J.-F. Lestrade, York University

Multi-epoch VLBI observations at 3.6 cm have been made of the RS~CVn binary star HR 8703 (IM Pegasi) in support of the NASA-Stanford relativity gyroscope experiment, Gravity Probe B (GP-B). We present phase-referenced maps of HR 8703 produced from thirteen sets of observations between January 1997 and December 1999. The maps reveal a variety of radio emission structures. Maps from temporal subsets of several observing sessions show both structural evolution in the stellar radio emission and submilliarcsecond motion of the radio brightness peak on hour time scales. We discuss what we have learned so far about the underlying processes responsible for the observed radio emission in HR 8703, and examine the implications for the GP-B experiment of our astrometric results to date.

P-37 Recent CCD Photometry of SX Phoenicis Stars

P.A. Delaney, R.M. Robb, A. Berndsen, R.M. Blake and H. Khosravani, York University

The SX Phoenicis stars are metal poor, population II stars in the process of evolving off the main sequence, characterized by pulsation periods of several hours and amplitudes of less than 0.7 magnitudes. Results are presented from the on-going photometric monitoring of several SX Phoenicis stars made at the York University Observatory as well as the automated Climenhaga Observatory, University of Victoria. A SpectraSource HPC-1 CCD and Photometrics Star I CCD were used at each observatory respectively. Times of extrema, period determinations, sample light curves and O-C diagrams are presented for BL Cam, XX Cyg and BE Lyn. All observations have been made since May 1999. Discussion and analysis of current results as well as their relationship with other recent results are given.

P-38 VSOP Imaging of the Radio-Emitting X-ray Binary Star LSI+61303

S.M. Dougherty, A.R. Taylor, W.K. Scott, M. Peracaula and J.M. Paredes, University of Calgary

LSI+61303 is one of the more unusual of known massive X-ray binary systems. It undergoes nonthermal radio outbursts every 26.5 days, attributed to the eccentric orbit of a gravitationally collapsed object orbiting within the dense circumstellar envelope of the B0e star primary. The relative gamma-ray to X-ray luminosity of the system is far higher than in any other known X-ray binary system, indicating a fundamentally different energy production mechanism. Despite several ground-based VLBI studies,the properties of the radio emission region remain unclear. Observations near peak flux density a few days after onset of the outburst indicate a very compact source ~1 mas in size, suggesting a low rate of expansion a few hundred km/s. However, observations at other epochs indicate initial expansion velocities of order ~0.06c that decelerate upon reaching dimensions of 2 mas. Other observations at quiescence, indicate a low level radio source with dimensions of ~4mas. A clear picture of the evolving radio emission, linking these diverse results remains elusive.

A primary difficulty with ground-based VLBI studies is that the variability time scale is short compared to the time required to obtain sufficient visibility coverage with a typical ground array. In this paper we report observations with the HALCA spacecraft in combination with a large array of ground radio telescopes. These data have been used to obtain, high-resolution, multi-epoch images of a radio outburst over a period of 48 hours, allowing, for the first time, an unambiguous picture of the dynamical evolution of the outburst ejecta from LSI +61303 on sub-mas scales.

P-39 Observations of a New Near Contact Eclipsing Binary System

M. T. Edalati, R. M. Robb, P. A. Delaney and A. Berndsen, Ferdowsi University of Mashhad, Iran

As a result of our search for photometric variations of stars exhibiting both emission lines and significant X-ray emission, we observed the field of LHS2178. A Photometrics STAR I CCD has been used in conjunction with the automated 0.5m telescope of the Climenhaga Observatory. We report here on the serendipitous discovery of a new eclipsing binary star system. The system has a period of 0.33 days and its light curve has been observed in R and I. The depth of the primary minimum is about 0.7 magnitudes in R. V,R,I colours for the system have been determined and suggest a spectral type of approximately K0. Preliminary modeling suggests a near contact system.

P-40 Light Curve Solutions for Eclipsing Binary Systems Containing Cepheid Variables

D. Lepischak and D.L. Welch, McMaster University and the MACHO Collaboration

Eclipsing binaries provide the most direct determination of the physical parameters of stellar systems. An eclipsing system with a variable star as one of the components produces an especially complicated light curve. If the system is also a double-lined spectroscopic binary it offers the only direct means to measure the mass of objects such as Cepheid variables. The MACHO database contains long-term photometric observations of four eclipsing Cepheid systems: the high-mass Cepheid 81.8997.87 and the low-mass Cepheids 78.6338.24 (HV 5756), 6.6454.5 and 5.4763.71. These all have bright (and stable) companions making them excellent double-line spectroscopic candidates. We present here the results of the first modelling of the lightcurves of these stars including orbital elements and dimensions of the system components and predictions of lightcurves for future eclipses.

P-41 The Distribution of Calcium on the Surface of Epsilon UMa: an Abundance Distribution Doppler Image

J.B. Rice, and D.E. Holmgren, Brandon University

We present a surface abundance Doppler image of singly-ionized calcium for the Bp star epsilon UMa based on high signal-to-noise CCD spectra. This map shows striking similarities to that of neutral oxygen (Rice et al, 1997). The Ca II 866.2 nm line has allowed us to obtain a detailed surface abundance map of calcium for epsilon UMa. The calcium abundance map has been used to locate the position of the positive magnetic pole on epsilon UMa at a longitude of 350.8 deg and a latitude of 25.8 deg. Calcium is distributed in a ring along the magnetic equator, along which the abundance is [Ca/H]=-5, which is close to a normal population I value. This represents an enhancement with respect to other regions by a factor of ~ 10^3. A secondary feature is present with [Ca/H]=-6.5. A chemically differentiated stellar wind is proposed as the main mechanism for generating the surface abundance distribution of calcium.

P-42 Revisiting The Classics

R.F. Garrison, C. Capobianco and C. Fayet, University of Toronto

The set of classical shell stars studied by Gulliver in the mid-1970s and by Merrill in the 1930s, 40s and 50s have been re-observed. The observations and reductions were carried out by two undergraduate students as part of a second-year, Research Opportunities Program at the University of Toronto. Shell stars have a wide variety of characteristics, which vary unpredictably, but with a characteristic timescale of the order of decades. A great deal can be learned by occasional monitoring of their spectra. This has not been done systematically since Gulliver's work. The 1.88-m telescope of the David Dunlap Observatory was used with the Cassegrain spectrograph and 1024x1024 CCD. The resulting two-pixel resolution is about one Angstrom. Description of the current shell characteristics is given.

P-43 A New Pulsating Star of the Beta Cephei Type

R. M. Robb, P. A. Delaney, R. D. Cardinal, D. Chaytor and A. Berndsen, University of Victoria

As part of out program of observing the ROSAT X-ray sources, we observed RX J0136.7+6125. The automated 0.5m telescope, Photometrics Star I CCD camera and R filter of the Climenhaga Observatory at the University of Victoria were used during the winters of 1996, 1997, and 2000. From our observations photometric variations were found in the adjacent star BD+60 282 = GSC 4031_631. The variations had a period of about 0.21 days and a peak to peak amplitude of about 0.06 in R. Neither the period nor the amplitude seemed constant. The spectral class of the star is B2II (Motch, 1997, private communication) leading us to believe that this star is a Beta Cephei type.

P-44 Pulsation of the Delta Scuti star V369 Scuti

V.A. Volk, E.F. Milone, K.M. Volk and W.J.F. Wilson, University of Calgary

V369 Scuti is a low amplitude, short period delta Scuti star. These are known to pulsate in multi-frequency radial and non-radial modes. Photoelectric and CCD differential photometry in BVRI from the Rothney Astrophysical Observatory, University of Calgary, and radial velocity measurements from spectra taken at the Dominion Astrophysical Observatory, Victoria, were obtained over the summers of 1997 through 1999. Fourier analyses of the resulting magnitude, colour and velocity curves reveal periods consistent with the published principal period of 0.223 day and its frequency 1 cpd aliases. Multiple frequencies are clearly evident, some of which correspond to p-mode oscillations expected by stellar pulsation models. Using Baade-Wesselink precepts, attempts are being made to describe the change in shape and luminosity of the star.

P-45 Radial Velocities of IAU Standard Stars

C. Scarfe, University of Victoria

As part of an ongoing international campaign, over 2000 radial-velocity observations of IAU standard stars have been obtained with the DAO radial-velocity scanner (RVS). In addition, over 100 new velocities from photographic plates have been added to those published ten years ago. The standard deviation of the RVS velocities is about three times larger than that of the photographic data. The RVS velocities were obtained with a variety of masks, but zero-point adjustments have been made empirically between them and between the RVS and the plates. An absolute zero-point has been provided by observations of bright asteroids. Comparison between the DAO data and large compilations published recently, by groups at the Center for Astrophysics and at the Geneva Observatory, reveals excellent agreement. In particular, a previously troublesome colour-dependent discrepancy between the Geneva observations and others has been eliminated, by adjustments made recently by the Geneva group, to an extent greater than even they had anticipated. The long task of revising the IAU standard system and providing a list of objects with radial velocities known absolutely to better than 100 m/s, and constant at the same level, now seems to be nearly complete.

P-46 Relaxation of Stressed Magnetic Structures, Current Dissipation and Electron Acceleration

K. Tapping, HIA / NRC

Magnetic structures containing trapped plasma are common in stellar atmospheres, planetary magnetospheres, and in the inter- stellar medium. The mean-free path may be comparable with spatial scales in the structures, so the electrical conductivity is problematic and the trapped plasma is best treated as a collection of particles rather than a fluid.

In general Curl B is non-zero, so electrical currents are present. These are carried through drifting of the charged particles trapped in the structures. Also, in general, there are asymmetries in the magnetic structures or properties of the particles that give rise to electrical fields, making the current flow dissipative. Potential energy in the distorted fields is dumped, allowing the magnetic fields to relax. If the required drift velocity for carrying the current is small compared with the thermal velocity, the current flow is stable. However, when this is not the case instabilities develop that can accelerate electrons to high energies.

In this paper we examine the role of inhomogeneities in the relaxation of stressed magnetic structures and a possible role in electron acceleration.

P-47 Magnetically Confined, Rotationally Modulated Stellar Winds of B and O type Stars

G.A. Wade, J.D. Landstreet, S.L.S. Shorlin and T.A.A. Sigut, University of Toronto

Many massive stars exhibit cyclic variability of their stellar winds on timescales compatible with their rotational periods. In this poster we discuss two such stars in which magnetic fields have recently been detected: the pulsating B1IIIe star Beta Cep and the young O7V star Theta 1 Ori C. We demonstrate that new MuSiCoS high-precision spectropolarimetric measurements of these stars are consistent with the presence of weak quasi-dipolar magnetic fields rooted in their photospheres, which couple to the wind and produce the observed line and continuum modulation in the optical, UV and X-ray.

P-48 Simulations of Planetary Transits of Stars in the Globular Cluster 47 Tucanae

M.D. Williams, E.F. Milone, M. McClure, J. Kallrath and S.J. Schiller, University of Calgary

In an attempt to answer some of the questions about planets with short orbital periods, Gilliland et al. conducted an eight day photometric search for planetary transits in the Globular cluster 47 Tucanae. For the purposes of predicting lightcurves that may be observed, a database of lightcurves was constructed. The database spans systems with planetary radius from half a Jupiter radius up to those of brown dwarfs. Since the problem of modelling planetary transits is similar to modelling the lightcurves of eclipsing binary stars, programs that were originally designed for binary stars were used to model the these systems. Two programs were used, the Wilson-Devinney (wd98k93) (Milone et al. in prep, Kallrath & Milone 1999) program and as an aid to constructing an archive, the visualization package Binary Maker 2 (Bradstreet 1993). In addition to predicting possible lightcurves, the database will also be used to speed up the modelling of observed systems by permitting the comparison of lightcurve properties such as the depth and the width of observed transits with those already modeled to estimate the system parameters. The parameters of the planetary system can then be refined using the Wilson-Devinney code and the method of differential corrections. The first observation of a planetary transit was made for the star HD209458. Photometric data from Charbonneau et al. and Henry et al. were used to determine the parameters, like planetary mass and radius, of the HD209458 system. More observations of HD209458 will be sought at the RAO this summer to better determine the system parameters. This work was supported by grants to EFM from the UofC Research Grants Committee and NSERC.

P-49 The Impact of Faint Binary Stars on the Kepler Search for Extrasolar Planets.

C. Ryan and J. Caldwell, York University

An analysis of HST deep-field images has been performed in support of a proposed NASA mission called Kepler. This mission will complete a photometric survey of 100,000 nearby main-sequence stars in search of transits by earth-sized planets. If such planets are common, and assuming that planetary orbital axes are oriented randomly, it is expected that Kepler will discover about 200 Earth-size planets in or near the habitable zone. At York University we have utilized pure parallel WFPC2 HST F606W data in the STScI archives to determine the number of faint (i.e. 20th to 25th magnitude) stars at various galactic latitudes near the equator. Since the target stars for the Kepler mission will be between 9th and 14th magnitude, a member of the fainter background population could in principle imitate the transit of a planetary companion if it is a binary that is not spatially resolved from the foreground target star by Kepler's optics. This could result in false positive signals. Our research will determine the statistical importance of this problem. Preliminary indications suggest that Kepler can significantly improve the background confusion issue by observing at approximately ten degrees above the equator.

P-50 Non-LTE Calculations for Mn II with Stratified Photospheric Abundance Profiles

T.A.A. Sigut, The University of Western Ontario

Recently, Sigut, Shorlin & Landstreet (2000, ApJ Letters 530, L89) have discovered weak, unexpected emission lines of Mn II, Hg II and P II in the red spectrum of the helium-3 star 3 Cen A and of Mn II in the HgMn star 46 Aql. To investigate the possible origin of these emission lines, detailed non-LTE calculations have been performed for Mn II in a host of model photospheres appropriate for the B stars. Interlocked non-LTE effects in this complex atomic model are examined to see if emission in any of the red Mn II multiplets is predicted. The response of the non-LTE predictions to parameterized photospheric abundance stratification is also investigated.

P-51 Stilling Poseidon: Apsidal Waves and Damping Neptune's Eccentricity

D. McNeil and M.J. Duncan, Queen's University

Neptune's eccentricity is anomalously low, and the loss of angular momentum to the Edgeworth-Kuiper belt by the creation of apsidal waves at the nu_8 precession resonance has recently been suggested by Ward and Hahn (1998) as a possible circularising mechanism. This project explores the interactions between Neptune and a self-gravitating disc by modifying Duncan, Levison and Lee's (1998) symplectic integrator package Swift_SyMBA to include a traditional particle mesh code for calculating intra-disc forces. Preliminary results from the simulations are presented. It is likely that the code will prove useful in studying the collective effects of the disc potential in the early solar system.

P-52 Counting All the Stars

P.A. Delaney and R.M. Robb, York University

With the increasing availability of inexpensive CCD cameras and the improving situation with computer-IRAF resources, a new laboratory exercise has been developed that exposes students to a variety of interesting and useful astronomical concepts. Assuming a homogeneous distribution of stars and no interstellar extinction, a plot of the logarithm of the number of stars as a function of magnitude will have a slope of 0.6. The students use a SBIG ST-8 (or comparable) CCD camera with a 28mm lens to obtain a wide field 10 second exposure of the night sky. After downloading this image into IRAF, DAOFIND is used to do the photometry to illustrate the relationship between the magnitude of the stars and the number of stars visible. When the students compare their results to the expected slope of 0.6, they find that it is significantly smaller. Discussion of this discrepancy illuminates the error in the assumptions. The same data can be used to crudely establish the central location of a cluster of stars. This exercise is useful at the first or second year astronomy undergraduate level.

P-53 An Adaptive Optics Device for Teaching Astronomy

R.M. Robb, E. Steinbring and P.A. Delaney, University of Victoria

The excitement of high resolution imaging generated by the relatively expensive adaptive optics (AO) systems on large telescopes can be communicated to students.

We purchased a tip-tilt AO system from the Santa Barbara Instruments Group for use with undergraduate labs at the University of Victoria. It has been mounted on a Celestron 8-inch located on the roof of our building. The ST-8 camera has an "imaging" CCD and mounted beside it is a small "guiding" CCD.

The guiding CCD is read a few times per second and the position of the guide star is found. A calculation is made to find the correction displacement to tip or tilt the right-angle mirror enough to keep the guide star on the same pixels. The light going to the "imaging" CCD reflects from the same tip/tilt mirror so its image is also corrected. While the results are not as dramatic as you might hope, we do measure a small decrease in the FWHM of the images we have obtained. The students learn about feedback in electromechanical systems and the structure of images.

P-54 The Karma Astronomical Visualisation Software

R. Gooch, University of Calgary

Modern astronomical instruments are producing larger and larger quantities of data, which require powerful computers to process and visualise. In particular, large three-dimensional datasets (such as the Canadian Galactic Plane Survey) stress the limits of the available hardware and visualisation software.

The Karma package is suite of visualisation tools designed for astronomical data and a powerful and flexible programming library which allows rapid development of production-quality visualisation tools. This package is in use in over thirty astronomical institutions around the world.

P-55 An Infrared Water Vapour Monitor for the Correction of Phase Errors in Submillimetre Astronomical Interferometry

D.A. Naylor and G.J. Smith, University of Lethbridge

The performance of existing and planned millimetre and submillimetre astronomical arrays is limited by fluctuations in the amount of atmospheric water vapour along the antenna's line of sight. Correcting the resulting phase distortion of the received signals is seen as a significant technological challenge. Measurements of the variation in the line-of-sight water vapour abundance at the level of 1 micron precipitable water vapour on a time scale of 1 second and at arbitrary antenna positions are required. In this paper we will present the design of, and preliminary results obtained with, a water vapour monitor operating at infrared wavelengths which shows considerable promise for this application. Improvements in, and future plans for, the second generation water vapour monitor currently under development will be discussed.

P-56 A Low-Power CCD System for Space Astronomy

G. Burley, D. Sinclair, R. Johnson and D. Foisy, Carnegie Observatories

A CCD camera for space applications must be versatile, low-power, and robust in the presence of radiation. The MOST micro-satellite will use two EEV charge-coupled devices, each with a 1024 x 1024 pixel imaging area. The CCD controller design is based on a programmable digital-signal processor, with low-power clock drivers and simple signal processing. Other enhancements include error-correcting memory, dual communication buses, and a temperature compensated precision clock.

MOST will incorporate a small (15-cm) optical telescope to perform long-duration stellar photometry observations.

P-57 A Further Improved Light Curve Modeling Package: WD98

E. Milone, C. R. Stagg, M.D. Williams, J. Kallrath, D. Terrell and W. Van Hamme, University of Calgary

Previously we developed a self-iterating, damped least-squares light curve modeling program that was built around the Wilson-Devinney code of ~1993, but augmented by Kurucz atmosphere models: WD95 (See Kallrath & Milone 1999 for a thorough discussion of the philosophy and practical considerations that led to this code). Meanwhile, Wilson (1998) further developed the basic code, replacing his least squares engine, expanding the treatment of reflection and limb-darkening, adding treatment of local scattering effects and allowing time as well as phase input data. We have now applied all our previous improvements to this new WD version; we call the package WD98. In addition, this version can generate a parameter grid with sequential variations of a certain parameter, e.g., the mass ratio. JK developed the code for this PC version. CRS adapted Wilson's 1998 code to a non-iterating but atmospheres-enhanced version that works on the the University of Calgary's Unix (AIX) platform; we call this AIX version wd98k93. In applying them to light curves, we make use of WVH's newly constructed limb-darkening tables for both solar and non-solar compositions, for bolometric and specific passbands, and DT's convenient desk-top two-way (T and log g) interpolator. We provide examples of the effectiveness of this new package. See also the paper by Williams, et al. This work has been supported by NSERC and the University of Calgary Research Grants Committee through grants to EFM.

P-58 Studying the Dispersion of VLBI Pulsar Data Using the Canadian S2 VLBI Correlator

D.A. Del Rizzo, N. Bartel, B.R. Carlson, W.T. Petrachenko and W.H. Cannon, York University/DRAO

A technique has been developed which allows for the investigation and removal of dispersion effects from VLBI pulsar data. This technique is made possible by using the Canadian S2 VLBI Correlator in Penticton. The high temporal and spectral resolution capabilities of this correlator are used to permit a detailed examination of dispersion and dispersion-removal effects on individual pulses, and a comparison of these effects - in magnitude and phase - from pulse to pulse over the duration of an observation. By applying this technique to strong, highly dispersed VLBI pulsar data, the structure of the dispersion curve over time both spatially, and as a function of sky frequency, can be examined in detail. An outline of our analysis procedure highlighted by examples from PSR 0329+54, observed using a data acquisition, recording and correlation system developed entirely in Canada, will be presented.

P-59 A Side-band Separating Balanced Mixer for ALMA

S. Claude, C. Cunningham, J. Sebesta, L. Martin and L. Avery, HIA / NRC

Current millimetre and sub-millimetre radio receivers generally rely on simple heterodyne mixers to down-convert the signal to the lower intermediate frequency. In this process the output of the mixer contains information received in both the upper and lower sidebands. This degrades the receiver performance, as noise from the sky enters the unused sideband. Also, it can result in confusion, as lines appearing in the spectrum can arise from either sideband. If offered, sideband separation is usually provided by a tunable interferometer that terminates the unwanted sideband on a cold load. The Atacama Large Millimetre Array (ALMA) will have 64 antennas, each requiring receivers for 10 separate frequency bands. It is clear that, for this project, interferometers cannot be used due to cost, size and reliability considerations. In this paper we describe a mixer design that separates the sidebands internally, and does so over a broad RF bandwidth. The mixer is physically very compact and has no moving parts. In addition, the mixer is balanced and, as a result, offers a very efficient means of local oscillator injection. This is especially important for the ALMA project where local oscillator power is required over large bandwidths at high frequencies. The mixer is a split waveguide design. One in-phase power splitter divides the input signal and a 90 degree out-of-phase 3dB hybrid coupler splits the local oscillator signal. After being combined using two 90 degree 3dB hybrid couplers, the signal and the local oscillator are injected into two balanced mixers. After down-conversion the IF signal is separated into upper and lower sidebands using a micro-strip 90 degree 3dB hybrid coupler.

P-60 The Chemical Abundances of Carina and Fornax Dwarf Spheroidal Galaxies

G.I. Mandushev, T.A. Smecker-Hane, J.E. Hesser, P.B. Stetson, G. S. Da Costa, and D. Hatzidimtriou, University of California at Irvine

We report on the chemical abundance distribution in the Carina and Fornax dwarf spheroidal galaxies (dSph) derived from low-resolution spectroscopy of red giant stars obtained at Cerro Tololo and the Anglo-Australian Observatory. We have determined values of [Fe/H] on the Carretta & Gratton (1997) scale for 72 stars in Carina dSph and 120 stars in Fornax dSph from the reduced equivalent width of the Ca II infrared triplet lines. The Carina dSph has a mean metallicity of [Fe/H] = -1.65 and an intrinsic metallicity dispersion of 0.39 dex, whereas the Fornax dSph has a mean metallicity of [Fe/H] = -1.07 and an intrinsic metallicity dispersion of 0.44 dex. By directly determining the chemical abundances of dSph stars through spectroscopy, we can overcome the age-metallicity degeneracy inherent in color-magnitude diagrams and determine their star-formation histories with unprecedented accuracy.