The Excess Density of Field Galaxies near z=0.56 around the Gamma-Ray Burst GRB021004 Position

Abstract

We test for reliability any signatures of field galaxies clustering in the GRB 021004 line of sight. The first signature is the GRB 021004 field photometric redshifts distribution based on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences observations with a peak near z ∼ 0.56 estimated from multicolor photometry in the GRB direction. The second signature is the Mg IIλλ2796, 2803 ÅÅ absorption doublet at z ≈ 0.56 in VLT/UVES spectra obtained for the GRB 021004 afterglow. The third signature is the galaxy clustering in a larger (of about 3 • × 3 • ) area around GRB 021004 with an effective peak near z ∼ 0.56 for both the spectral and photometric redshifts from a few catalogs of clusters based on the Sloan Digital Sky Survey (SDSS) and Baryon Oscillation Spectroscopic Survey (BOSS) as a part of SDSS-III. From catalog data the size of the whole inhomogeneity in distribution of the galaxy clusters with the peak near z ≈ 0.56 is also estimated as about 6 • -8 • or 140-190 Mpc. A possibility of inhomogeneity (a galaxy cluster) near the GRB 021004 direction can be also confirmed by an inhomogeneity in the cosmic microwave background related with the Sunyaev-Zeldovich effect.