The spatial distribution of galaxies within the CMB cold spot in the Corona Borealis supercluster

Padilla-Torres, C. P.
Gutierrez, C. M.
Rebolo, R.
Genova-Santos, R.
Rubino-Martin, J. A.
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We study the spatial distribution and colours of galaxies within the region covered by the cold spot in the cosmic microwave background (CMB) recently detected by the Very Small Array (VSA; Genova-Santos et al. 2005, 2008) towards the Corona Borealis supercluster (CrB-SC). The spot is in the northern part of a region with a radius ~1 degree (~5 Mpc at the redshift of CrB-SC) enclosing the clusters Abell 2056, 2065, 2059 and 2073, and where the density of galaxies, excluding the contribution from those clusters, is ~2 times higher than the mean value in typical intercluster regions of the CrB-SC. Two of such clusters (Abell 2056 and 2065) are members of the CrB-SC, while the other two are in the background. This high density intercluster region is quite inhomogeneous, being the most remarkable feature a large concentration of galaxies in a narrow filament running from Abell 2065 with a length of ~35 arcmin (~3 Mpc at the redshift of CrB-SC) in the SW-NE direction. This intercluster population of galaxies probably results from the interaction of clusters Abell 2065 and 2056. The area subtended by the VSA cold spot shows an excess of faint (21<r<22) and red (1.1<r-i<1.3) galaxies as compared with typical values within the CrB-SC intercluster regions. This overdensity of galaxies shows a radial dependence and extends out to ~15 arcmin. This could be signature of a previously unnoticed cluster in the background.
Comment: Accepted for publication in MNRAS
Astrophysics - Cosmology and Nongalactic Astrophysics