A First Determination of the Surface Density of Galaxy Clusters at Very Low X-Ray Fluxes
Abstract
We present the first results of a serendipitous search for clusters of galaxies in deep ROSAT PSPC pointed observations at high Galactic latitude. The survey is being carried out using a wavelet-based detection algorithm which is not biased against extended, low surface brightness sources. A new flux-diameter limited sample of 10 cluster candidates has been created from ~3 deg^2^ surveyed area. Preliminary CCD observations have revealed that a large fraction of these candidates correspond to a visible enhancement in the galaxy surface density, and several others have been identified from other surveys. We believe these sources to be either low- to moderate-redshift groups or intermediate- to high-redshift clusters. We show X-ray and optical images of some of the clusters identified to date. We present, for the first time, the derived number density of the galaxy clusters to a flux limit of 1 x 10^-14^ ergs cm^-2^ s^-1^ (0.5-2.0 keV). This extends the log N-log S of previous cluster surveys by more than one decade in flux. Results are compared to theoretical predictions for cluster number counts.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1995
- DOI:
- 10.1086/187877
- arXiv:
- arXiv:astro-ph/9503064
- Bibcode:
- 1995ApJ...445L..11R
- Keywords:
-
- Galactic Clusters;
- Radiant Flux Density;
- Surface Properties;
- X Ray Astronomy;
- X Ray Imagery;
- X Rays;
- Algorithms;
- Image Processing;
- Red Shift;
- Rosat Mission;
- Astrophysics;
- GALAXIES: CLUSTERS: GENERAL;
- TECHNIQUES: IMAGE PROCESSING;
- X-RAYS: GALAXIES;
- X-RAYS: GENERAL;
- Astrophysics
- E-Print:
- uuencoded compressed Postscript, 7 pages including 4 figures. Accepted for publication in Ap. J. Letters.