2009/08/27 by Audrey Galametz, A. Galametz, Carlos De Breuck +14
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Brightest cluster galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Luminous infrared galaxy #Physics #Radio galaxy #Redshift #astro-ph.CO
paper · pdf · doi:10.1051/0004-6361/200912177
21 pages, 12 figures, 6 tables, accepted for publication in A&A
arxiv created 2009/08/27 · openalex publication_date 2009/09/03 · arxiv updated 2015/05/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We explore the environments of two radio galaxies at <i>z<i/> ~ 1.5, 7C 1751+6809 and 7C 1756+6520, using deep optical and near-infrared imaging. Our data cover 1515 arcmin<sup>2<sup/> fields around the radio galaxies. We develop and apply <i>BzK<i/> color criteria to select cluster member candidates around the radio galaxies and find no evidence of an overdensity of red galaxies within 2 Mpc of 7C 1751+6809. In contrast, 7C 1756+6520 shows a significant overdensity of red galaxies within 2 Mpc of the radio galaxy, by a factor of 3.1<i>±<i/>0.8 relative to the four MUSYC fields. At small separation (<i>r<i/> < 6″), this radio galaxy also has one evolved galaxy candidate, one <i>z<i/> > 1.4 star-forming galaxy candidate, and an AGN candidate (at indeterminate redshift). This is suggestive of several close-by companions. Several concentrations of red galaxies are also noticed in the full 7C 1756+6520 field, forming a possible large-scale structure of evolved galaxies with a NW-SE orientation. We construct the color-magnitude diagram of red galaxies found near 7C 1756+6520 (<i>r<i/> < 2 Mpc), and find a clear red sequence that is truncated at <i>K<i/><sub>s<sub/> ~ 21.5 (AB). We also find an overdensity of mid-infrared selected AGN in the surroundings of 7C 1756+6520. These results are suggestive of a proto-cluster at high redshift.