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

¹ Department of Space and Climate Physics, University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Surrey, UK
² SRON Laboratory for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands
³ Institute of Astronomy, University of Cambridge, Madingly Road, Cambridge, CB3 0HA, UK
⁴ NASA/GSFC, Code 662, Greenbelt, MD 20771, USA
⁵ Columbia Astrophysics Laboratory and Department of Physics, Columbia University, 538 West 120th Street, New York, NY 10027, USA
⁶ Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
⁷ Atrophysics Division, European Space Agency, ESTEC, Postbus 299, 2200AG Noordwijk, The Netherlands
⁸ Department of Physics and Astronomy, The University of Leicester, Leicester, LE1 7RH, UK
⁹ Los Alamos National Laboratory, NIS-2, Los Alamos, NM 87545, USA

J. Mittaz

Received: 2 October 2000
Accepted: 5 November 2000

Abstract

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 Hα, 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 at the centre of this cluster.