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arXiv · 2203.02208

The 700 ks Chandra Spiderweb Field I: evidence for widespread nuclear activity in the Protocluster

P. Tozzi·L. Pentericci·R. Gilli·M. Pannella·F. Fiore·G. Miley·M. Nonino·H. J. A. Rottgering·V. Strazzullo·C. S. Anderson·S. Borgani·A. Calabro'·C. Carilli·H. Dannerbauer·L. Di Mascolo·C. Feruglio·R. Gobat·S. Jin·A. Liu·T. Mroczkowski·C. Norman·E. Rasia·P. Rosati·A. Saro
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Abstract

(Abridged) We present an analysis of the 700 ks Chandra ACIS-S observation of the field around the Spiderweb Galaxy at z=2.156, focusing on the nuclear activity in the associated large-scale environment. We identify unresolved X-ray sources down to flux limits of 1.3X10^{-16} and 3.9X10^{-16} erg/s/cm^2 in the soft and hard band, respectively. We search for counterparts in the optical, NIR and submm bands to identify X-ray sources belonging to the protocluster. We detect 107 X-ray unresolved sources within 5 arcmin (corresponding to 2.5 Mpc) of J1140-2629, among which 13 have optical counterparts with spectroscopic redshift 2.11 ~1.84+-0.04. The best-fit intrinsic absorption for 5 protocluster X-ray members is N_H>10^{23} cm^{-2}, while other 6 have upper limits of the order of fewX10^{22} cm^{-2}. Two sources can only be fitted with very flat \Gamma<=1, and are therefore considered Compton-thick candidates. Their 0.5-10 keV rest frame luminosities are larger than 2X10^{43} erg/s, significantly greater than X-ray luminosities expected from star formation activity. The X-ray luminosity function of AGN in the volume associated to the Spiderweb protocluster in the range 10^{43} 10.5, corresponding to an enhancement of 6.0^{+9.0}_{-3.0} with respect to the COSMOS field at comparable redshifts and stellar mass range. We conclude that the galaxy population in the Spiderweb Protocluster is characterized by enhanced X-ray nuclear activity triggered by environmental effects on Mpc scales.

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P. Tozzi, L. Pentericci, R. Gilli, M. Pannella, F. Fiore, G. Miley, M. Nonino, H. J. A. Rottgering, V. Strazzullo, C. S. Anderson, S. Borgani, A. Calabro', C. Carilli, H. Dannerbauer, L. Di Mascolo, C. Feruglio, R. Gobat, S. Jin, A. Liu, T. Mroczkowski, C. Norman, E. Rasia, P. Rosati, A. Saro. 2022-03-04. The 700 ks Chandra Spiderweb Field I: evidence for widespread nuclear activity in the Protocluster. https://doi.org/10.1051/0004-6361/202142333

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