Fossil Groups in the Sloan Digital Sky Survey
نویسندگان
چکیده
A search for fossil groups in the Sloan Digital Sky Survey was performed using virtual observatory tools. A cross-match of the positions of all SDSS Luminous Red Galaxies (with r < 19 and measured spectroscopic redshifts) with sources in the ROSAT All-Sky Survey catalog resulted in a list of elliptical galaxies with extended X-ray emission (with a galaxy/ROSAT-source distance of less than 0.5 arcmin in all cases). A search for neighbors of the selected elliptical galaxies within a radius of 0.5h 70 Mpc was conducted taking into account the r-band magnitudes and spectroscopic or photometric redshifts of all objects within this area, leading to a sample of 34 candidate fossil groups. Considering this sample, the estimated space density of fossil systems is n = (1.0± 0.6)× 10 h50 Mpc . Subject headings: astronomical data bases: miscellaneous — galaxies: elliptical and lenticular, cD — galaxies: clusters: general — X-rays: galaxies: clusters
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