Gretchen Harris

Associate Professor
Undergraduate Officer

Office: PHY 251
Phone: (519) 888-4567 ext. 36856
Email: glharris@uwaterloo.ca

Research interests

• Spectroscopic and photometric studies of globular clusters in the Galaxy and extragalactic systems
• Stellar populations in galaxies
• Open clusters

Teaching activities

My main love in teaching is, of course, astronomy. At present, I teach an overview of the solar system (Physics 275) and stellar astrophysics (Physics 375). In addition to these our astronomy group offers an introductory survey course for science majors (Sci 238) and non-science students (Sci 237), and a fourth year galaxies and cosmology course (Physics 475). I have also prepared a version of Sci 238 which is offered by the University of Waterloo Distance Education program.

One of the greatest sources of satisfaction for me here at Waterloo is working with undergraduate students on research projects, both as summer research assistants and through the Physics 437 senior research project.

Research activities

Globular clusters (age ~ 12-15Gyr) are found in the haloes of all known types of galaxies and are thus important dynamical, chemical and evolutionary archaeological probes of all stages of galaxy information. The growing database for extragalactic globular clusters shows them to be similar from galaxy to galaxy, making them also important calibrators of the extragalactic distance scale.

However, the fundamental calibrating database remains strongly restricted to our spiral galaxy (the Milky Way), while most of the extragalatic studies are of elliptical galaxies. My research in this area has involved studies of Milky Way globular clusters, those in our "twin" neighbouring galaxy (M31 in Andromeda), the nearest large elliptical (NGC5128) and the more distant E/SO galaxies NGC1379, NGC6861, and M87. The primary goals of these studies are to a) define the total cluster population and its spatial distribution and compare these properties with other globular cluster systems (GSCs) and b) determine and interpret the abundance properties of GSCs - both internally and in comparison with other systems.

Recent results in various spectroscopic and photometric systems have demonstrated that abundance determinations from the most metal-rich extragalactic globular clusters are highly suspect. At present we have metallicity distributions for only a few dozen galaxies, but they are suggestive of a wide range of enrichment histories, possibly significantly different for spirals and ellipticals.

My main interests are in the improvement of data for a few nearby cluster systems for which we may be able to reduce current uncertainties, verify the nature of these objects as old stellar systems, and establish a small number of fundamental calibrator GSCs in addition to our own Milky Way. Some of my current work includes the first color-magnitude diagram of a globular cluster outside the Local Group of galaxies the stunning discovery that the gas in the newly forming NGC5128 must have gone through an early and rapid enrichment phase to leave it with very old stars whose heavy element abundances are as low as the most metal-poor in the Milky Way halo to as metal-rich as the Sun, and the finding that the cluster luminosity function in the innermost regions of the M87 GSC is virtually identical to that for outer clusters - calling into question many dynamical models related to the disruption of clusters throughout their lifetimes.

Other work in progress includes the determination of spectroscopic abundances of NGC5128 clusters, the use of the new wider-field "mosaic" CCD imagers to provide a more detailed and thorough understanding of the spatial, luminosity and abundance properties of a select few nearby cluster systems, and further WFPC2 imaging of stellar halo fields in NGC 5128.

Selected publications

• G.L.H. Harris, D. Geisler, H.C. Harris and J. Hesser. 1992. Metal Abundances from Washington Photometry of Globular Clusters in NGC 5128. A.J. 104, 613.
• G.L.H. Harris, M.P. FitzGerald, S. Mehta, and B.C. Reed. 1993. NGC 2287 - An Important Intermediate-Age Open Cluster. A.J. 106, 1533.
• L.G. Reed, G.L.H. Harris, and W.E. Harris. 1994. Integrated BVR Photometry of Halo Globular Cluster in M31 II. A.J. 107, 555.
• D.L. Wing, G.L.H. Harris, D.A. Hanes and W.E. Harris. 1995. Measuring Distant Globular Cluster Systems Using Brightness Fluctuations. A.J. 109, 121.
• P. Cote, D.A. Hanes, D.E. McLaughlin, T.J. Bridges, J.E. Hesser and G.L.H. Harris. 1997. Discovery of a Probable CH Star in the Globular Cluster M14 and Implications for the Evolution of Binaries in Clusters. Ap. J. Lett. 476, L15.
• W.E. Harris, G.L.H. Harris, and D.E. McLaughlin. 1998. M87, Globular Clusters and Galactic Winds: Issues in Giant Galaxy Formation. A.J. 115, 1801.
• G.L.H. Harris, G.B. Poole and W.E. Harris. 1998. A Color-Magnitude Diagram for a Globular Cluster in the Giant Elliptical Galaxy NGC 5128, A.J. 116, 2866.
• G.L.H. Harris, W.E. Harris, and G.B Poole. 1999. The Metallicity Distribution in the Halo Stars of NGC 5128: Implications for Galaxy Formation, A.J. 117, 855.