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Detection of overdensity excess of field galaxies near
a redshift of z≈0.56 around the gamma-ray burst
GRB 021004 position

Russian version

    From observations carried out with the telescopes BTA/SCORPIO and VLT/UVES and from data of new catalogs SDSS-III and others, the characteristic signatures of the clustering of field galaxies with a redshift of z≈0.56 around the gamma-ray burst GRB 021004 position were detected.
    1. From data of multiband BVRI photometry of 263 galaxies (16<B<∼28-th st.magn.) in the BTA field of size ∼4'×4' in direction of this gamma-ray burst (with account for HST/ACS photometry), the distribution of photometric redshifts shows a peak at z≈0.56.
    2. The Mg II2796/2803Å (fig. 2) absorption doublet at a redshift of z=0.56 as detected in the VLT/UVES spectra of GRB 021004 afterglow (with the proper redshift zš=š2.33), i.e. for galaxy clusters with z≈0.56 being around the line of sight of this gamma-ray burst.
    3.The clustering of galaxies was detected in a larger area (∼3×3 sq. degrees) around GRBš021004 position with the effective peak near z≈0.56 (fig. 3), detectable from distributions of spectral and photometric z with the use of new catalogs of galaxy clusters based on data of the Sloan Digital Sky Survey III and also its part, the Baryon Oscillation Spectroscopic Survey.
    4.From data of 6 catalogs (with the depth in r<21.5 st.magn. for photometric and B<23 st.magn. for spectral redshifts z) the size of the whole inhomogeneity in distribution of galaxy clusters – a supercluster with a peak near z≈0.56, was estimated as ∼7°±1°.
    1) Ilya V. Sokolov, Oskar J.A. Bravo Calle and Yu.V. Baryshev , “ Study of BTA, Hubble, and Spitzer GRB 021004 deep field”, Gamma–ray Bursts: 15 Years of GRB Afterglows – Progenitors, Environments and Host Galaxies from the Nearby to the Early Universe (A.J. Castro-Tirado, J.Gorosabel and I.H. Park (eds)), EAS Publications Series, 61 (2013) 435-437 (DOI: 10.1051/eas/1361070)
    2) Sokolov, Ilya V.; Castro-Tirado, A. J.; Verkhodanov, O. V.; Zhelenkova, O. P.; Baryshev, Yu. V., “Clustering of galaxies around the GRB 021004 sight-line at z∼0.5” in “Proceedings of the International Workshop on Quark Phase Transition in Compact Objects and Multimessenger Astronomy: Neutrino Signals, Supernovae and Gamma-Ray Bursts”, Russia, Nizhnij Arkhyz (SAO RAS), Terskol (BNO INR RAS), October, 7 – 14, 2015, pp. 111, Publishing house “Sneg”, Pyatigorsk, 2016. http://adsabs.harvard.edu/abs/2016qptc.conf..111S see pg.111https://www.sao.ru/hq/grb/conf_2015/Proc_SAO-BNO-2015_final_full.pdf
    3) Yu. V. Baryshev, Ilya V. Sokolov, Alex S. Moskvitin et al., “Study of Faint Galaxies in the Field of GRB 021004”, Astrophysical Bulletin, 65, 311 (2010), http://arxiv.org/abs/1010.3910 https://www.sao.ru/Doc-k8/Science/Public/Bulletin/Vol65/N4/p327.pdf.
    4) Sokolov Ilya V., Zhelenkova Olga P., Solovyev Ilya A., Castro-Tirado Alberto J., and Verkhodanov Oleg V., “ The field galaxies clustering in GRB 021004 line of sight and in the larger areas with an effective peak near z≈0.56.” (submitted in the Astrophysical Bulletin).

Ilya Sokolov
Alberto J. Castro-Tirado
Olga Zhelenkova
Yurii Baryshev
Fig.1. Photometric redshift distribution of galaxies with a peak near to z≈0.56 in the BTA GRBš021004 field (of the size ∼4'×4') estimated from BTA multicolor BVRI photometry (+HST/ACS data) of 277 galaxies in direction of this GRB. Fig.2. The Mg II 2796/2803Å absorption doublet at z≈0.56 in the GRB 021004 afterglow VLT/UVES spectra obtained for the afterglow. Fig.3. The galaxy clustering in a larger (∼3 × sq. degrees) rea around GRB 021004 with an effective peak near z≈0.56 for spectral and photometric redshift distributions from new catalogs with galaxy clusters.