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Session 110 - Imaging of Cluster Galaxies.
Display session, Thursday, January 18
North Banquet Hall, Convention Center
We present an image of the Abell 1795 cD galaxy and its environment obtained with the Goddard Ultraviolet Imaging Telescope (UIT). Our ultraviolet (UV) image was obtained during the March 1995 Astro-2 Space Shuttle mission using a filter centered at \sim\!1520Å\/ (\Delta\lambda=354Å\/). The ultraviolet image resulting from a 1310 second exposure has stellar images with \sim5.0\arcsec FWHM. We compare these data to published optical, radio (VLA) and archival HST observations. This richness class 2 cluster is known to contain a large cooling flow (\dotM\sim 300M_\sun yr^-1) and its cD galaxy contains a relatively bright yet small radio source (4C26.42). Previous optical observations have shown the cD galaxy possesses a system of H\alpha filaments (van Breugel et al.\/ 1984, ApJ, 276, 79), whose surface brightness is consistent with models in which the emission--lines arise from radiatively regulated accretion (i.e.\/ cooling X--ray gas). Broad-band optical investigations have revealed the presence of ``blue lobes'' near the cD galaxy center. These regions are posited to contain young stars formed via the interaction of a radio jet and the intercluster medium (McNamara amp; O'Connell 1993, AJ, 105, 417). The HST observations show the elliptical galaxy has an easily resolved dust lane structure near its center. The cD galaxy is very bright in the ultraviolet (m_1520=15.1) and exhibits a strong radial color gradient with the center being bluer. Indeed, UV light is detected from the central 7.6\arcsec\times16.1\arcsec (8.4\times17.7 kpc) which can be compared with the optical extents of 38\arcsec\times70\arcsec. We discuss the implications that our new UV data have for the high mass star formation rate, and examine how our photometry fits in with previous models for the unusual features present in the system. Most of the other cluster galaxies are not detected. We report photometry and predicted star formation rates for those that were seen along with upper limits for those galaxies not detected.
