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[62.06] X-ray Galaxy groups in COSMOS

A. Finoguenov (MPE & JCA UMBC), COSMOS Collaboration

We present the results of a search for galaxy clusters in the first year of XMM-Newton observation of the COSMOS field reaching an unprecedented flux depth for a cluster flux of 2 x 10^-15 ergs cm^-2 s^-1 for its area of 2.2 square degrees, which allows a detection of galaxy groups to a redshift of 0.5, and a Virgo cluster to a redshift of 1.5. Applying a wavelet reconstruction technique to the XMM mosaic of the field in the 0.5-2 keV band, we select 130 clusters candidates. The broad-band imaging, gained to date for the COSMOS field, allows a robust estimate of the photometric redshift for galaxies down to 25 magnitude in I_AB. The current near-infrared coverage (z and K bands) allows to make photo-z estimates to a redshift of 1.4. Using photo-z slices of d z=0.2 and selecting the early-type galaxies, we run an independent cluster search to identify 360 early-type galaxy concentrations in the redshift range 01. Based on these results we provide the logN-logS of the survey and dN/dz. Below redshift of 0.5, where our sensitivity limits allow to detect galaxy groups, a half of the galaxy concentrations, identified in the photo-z has a corresponding diffuse X-ray source. We identify three redshift peaks in the distribution of clusters, located at z=0.4, z=0.7 and the largest one at z=0.9. These results provide well-defined information on the LSS in the COSMOS field and allow a follow-up study of the evolution in the galaxy morphology in dense environments.

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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.