UV observations of the galaxy cluster Abell 1795 with the optical monitor on XMM-Newton

We present the results of an analysis of broad band UV observations of the central regions of Abell 1795 observed with the optical monitor on XMM-Newton. As have been found with other UV observations of the central regions of clusters of galaxies, we find evidence for star formation. However, we also find evidence for absorption in the cD galaxy on a more extended scale than has been seen with optical imaging. We also report the first UV observation of part of the filamentary structure seen in H-alpha, X-rays and very deep U band imaging. The part of the filament we see is very blue with UV colours consistent with a very early (O/B) stellar population. This is the first direct evidence of a dominant population of early type stars at the centre of Abell 1795 and implies very recent star formation. The relationship of this emission to emission at other wavebands is discussed.

[1]  Brian R. McNamara,et al.  Blue lobe galaxies in the cooling flow clusters Abell 1795 and Abell 2597 , 1993 .

[2]  Alan Dressler,et al.  Ultraviolet Imaging of the Galaxy Cluster CL 0939+4713 (Abell 851) at z=0.41 , 1999, astro-ph/9910094.

[3]  Brian R. McNamara,et al.  Optical Structure in the Abell 1795 Cluster Central Galaxy: Evidence for Stripping and Deflection of Radio Jets , 1996 .

[4]  Brian R. McNamara,et al.  X-ray-emitting filaments in the cooling flow cluster A2029 , 1992 .

[5]  L. Cowie,et al.  Long-slit spectroscopy of gas in the cores of X-ray luminous clusters , 1985 .

[6]  Glenn E. Miller,et al.  The Initial mass function and stellar birthrate in the solar neighborhood , 1979 .

[7]  Lennox L. Cowie,et al.  Two-dimensional spectrophotometry of the cores of X-ray luminous clusters , 1983 .

[8]  Steven W. Allen,et al.  Starbursts in cooling flows: blue continua and emission-line nebulae in central cluster galaxies , 1995 .

[9]  Laurence P. David,et al.  MAPPING THE DARK MATTER IN THE NGC 5044 GROUP WITH ROSAT : EVIDENCE FOR A NEARLY HOMOGENEOUS COOLING FLOW WITH A COOLING WAKE , 1994 .

[10]  G. Mark Voit,et al.  Self-irradiated cooling condensations - The source of the optical line emission from cooling flows , 1990 .

[11]  S. Ettori,et al.  Chandra imaging of the complex X-ray core of the Perseus cluster , 2000, astro-ph/0007456.

[12]  H. Thronson,et al.  Dust and the transfer of stellar radiation within galaxies , 1991 .

[13]  USA,et al.  Measuring cluster temperature profiles with XMM/EPIC , 2000, astro-ph/0011198.

[14]  Los Alamos National Lab,et al.  The XMM-Newton optical/UV monitor telescope , 2000, astro-ph/0011216.

[15]  G. D. Bothun,et al.  Ultraviolet Imaging Observations of the cD Galaxy in Abell 1795: Further Evidence for Massive Star Formation in a Cooling Flow , 1996, astro-ph/9611024.

[16]  S. Charlot,et al.  Spectral evolution of stellar populations using isochrone synthesis , 1993 .

[17]  Patrick J. McCarthy,et al.  Dynamical, physical, and chemical properties of emission-line nebulae in cooling flows , 1989 .

[18]  Marshall W. Bautz,et al.  ASCA observations of cooling flows in clusters of galaxies , 1994 .

[19]  E. Hu,et al.  LY alpha Emission from Cooling Flows and Measures of the Dust Content of Rich Clusters of Galaxies , 1992 .

[20]  A. Pickles.  A Stellar Spectral Flux Library: 1150–25000 Å , 1998 .

[21]  William R. Oegerle,et al.  Dynamics of cD clusters of galaxies. II: Analysis of seven Abell clusters , 1994 .