2007/03/16 by Fabio Gastaldello, F. Gastaldello, David A. Buote +7 · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/518304
published as Astrophys.J.662:923-926,2007 · 5 pages, 4 colour figures, accepted for publication in ApJ
arxiv created 2007/03/16 · openalex publication_date 2007/06/12 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We report the discovery of a galaxy cluster serendipitously detected as an extended X-ray source in an offset observation of the group NGC 5044. The cluster redshift, z = 0.281, determined from the optical spectrum of the brightest cluster galaxy, agrees with that inferred from the X-ray spectrum using the Fe Kα complex of the hot ICM ( z = 0.27 ± 0.01). Based on the 50 ks XMM-Newton observation, we find that within a radius of 383 kpc the cluster has an unabsorbed X-ray flux f X (0.5-2 keV) = (3.34 ) × 10 -13 ergs cm -2 s -1 , a bolometric X-ray luminosity L X = (2.21 ) × 10 44 ergs s -1 , kT = 3.57 ± 0.12 keV, and metallicity 0.60 ± 0.09 Z ☉ . The cluster obeys the scaling relations for L X and T observed at intermediate redshift. The mass derived from an isothermal NFW model fit is M vir = 3.89 ± 0.35 × 10 14 M ☉ , with a concentration parameter, c = 6.7 ± 0.4, consistent with the range of values expected in the concordance cosmological model for relaxed clusters. The optical properties suggest this could be a "fossil cluster."