Deborah B. Haarsma: Research

In my research, I pursue questions about galaxies and the universe as a whole. Galaxies and galaxy clusters emit light in all parts of the electromagnetic spectrum, and I have used telescopes that detect radio, infrared, optical, and X-ray light. In galaxy clusters, hot gas fills the space between the galaxies, and that hot gas emits X-rays. Typically, a cluster has one large galaxy at the center (called the Brightest Cluster Galaxy, or BCG). In my current project, my team has found a special relationship between the BCG and the hot gas at the core of the cluster, suggesting that both the stars and the gas have their density set by the long merger history of the clutser (in the absence of feedback from supernova explosions or black holes). My students and I collaborate with Prof. Megan Donahue and Prof. Mark Voit at Michigan State University, as well as astronomers in Germany, the U.K., France, and Italy.

Prior to my work on galaxy clusters, most of my work wasin the area of gravitational lensing, a phenomenon of general relativity in which light is bent by gravitational fields, distorting and multiplying the images of distantgalaxies. Gravitational lenses can be used to determine the mass and dark matter content of galaxies by measuring their effect on more distant radio sources. Gravitational lenses can also be used to determine the expansion rate of the universe, its mass density, and the cosmological constant, which in turn determine the age, curvature, and future of the universe. I have also studied the changes in the properties of galaxies over the history of the universe, using the faint radio emission of distant young galaxies.

Refereed Journal Articles:

``Brightest Cluster Galaxies and Core Gas Density in REXCESS Clusters."
Haarsma, D. B., Leisman, L., Donahue, M., Bruch, S., Bohringer, H., Croston, J. H., Pratt, G. W., Voit, G. M., Arnaud, M., Pierini, D.
Submitted to Astrophysical Journal August 2009

``The Central Component of Gravitational Lens Q0957+561."
Haarsma, D. B., Winn, J. N., Shapiro, I., Lehar, J. 2005
Astronomical Journal, 130, 1977.

``The FIRST-Optical-VLA Survey for Lensed Radio Lobes."
Haarsma, D. B., Winn, J. N., Falco, E. E., Kochanek, C. S., Ammar, P., Boersma, C., Fogwell, S., Muxlow, T. W. B., McLeod, B. A., Lehar, J. 2005
Astronomical Journal, 130, 1977.

``VLA-FIRST/GB6 inverted-spectrum radio sources at 20 GHz.''
Guerra, E. J., Newlands, S. M., Haarsma, D. B., Partridge, R. B. 2002
New Astronomy Reviews, 46, 303.

``Toward a Resolution of the Discrepancy Between Different Estimators of Star Formation Rate.''
Hopkins, A. M., Connolly, A. J., Haarsma, D. B., and Cram, L. E. 2001
Astronomical Journal, 122, 288.

``Further investigation of the time delay, magnification ratios, and variability in the gravitational lens 0218+357.''
Cohen, A. S., Hewitt, J. N., Moore, C. B., Haarsma, D. B. 2000
Astrophysical Journal, 545, 578.

``Faint Radio Sources and Star Formation History.''
Haarsma, D. B., Partridge, R. B., Windhorst, R. A., and Richards, E. A. 2000.
Astrophysical Journal, 544, 651

``The Radio Wavelength Time Delay of Gravitational Lens 0957+561.''
Haarsma, D. B., Hewitt, J. N., Lehar, J., Burke, B. F. 1999.
Astrophysical Journal, 510, 64.

``Radio Wavelength Constraints on the Sources of the Far Infrared Background.''
Haarsma, D. B., Partridge, R. B. 1998.
Astrophysical Journal, 503, L5.

``Low Surface Brightness Radio Structure in the Field of Gravitational Lens 0957+561,''
Avruch, I. M., Cohen, A. S., Lehar, J., Conner, S. R., Haarsma, D. B., Burke, B. F. 1997.
Astrophysical Journal, 488, L121.

``The 6 cm Light Curves of B0957+561, 1979-1994: New Features and Implications for the Time Delay,''
Haarsma, D. B., Hewitt, J. N., Lehar, J., Burke, B. F. 1997.
Astrophysical Journal, 479, 102.

Content updated August 2009