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The Cosmic Evolution Survey (COSMOS): A Large‐Scale Structure at <i>z</i> = 0.73 and the Relation of Galaxy Morphologies to Local Environment

L. GuzzoINAF-Osservatorio Astronomico di Brera, I-23807, Merate (LC), ItalyP. CassataDipartimento di Astronomia, Università di Padova, I-35100 Padova, ItalyA FinoguenovMax-Planck Institut für Extraterrestrische Physik, Garching, GermanyR. MasseyCalifornia Institute of Technology, MC 105-24, Pasadena, CA 91125Ekta A. ShahCalifornia Institute of Technology, MC 105-24, Pasadena, CA 91125P. CapakCalifornia Institute of Technology, MC 105-24, Pasadena, CA 91125Richard S. EllisCalifornia Institute of Technology, MC 105-24, Pasadena, CA 91125B. MobasherSpace Telescope Science Institute, Baltimore, MD 21218Yoshiaki TaniguchiAstronomical Institute, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, JapanD. J. ThompsonCalifornia Institute of Technology, MC 105-24, Pasadena, CA 91125M. AjikiAstronomical Institute, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, JapanH. AusselService d’Astrophysique, CEA/Saclay, 91191 Gif-sur-Yvette, FranceH. BöhringerMax-Planck Institut für Extraterrestrische Physik, Garching, GermanyM. BrusaMax-Planck Institut für Extraterrestrische Physik, Garching, GermanyDaniela CalzettiSpace Telescope Science Institute, Baltimore, MD 21218A. ComastriINAF-Osservatorio Astronomico di Bologna, Bologna, ItalyA. FranceschiniDipartimento di Astronomia, Università di Padova, I-35100 Padova, ItalyG. HasingerMax-Planck Institut für Extraterrestrische Physik, Garching, GermanyM. M. KasliwalCalifornia Institute of Technology, MC 105-24, Pasadena, CA 91125Manfred G. KitzbichlerMax-Planck-Institut für Astrophysik, D-85748 Garching bei München, GermanyJean‐Paul KneibLaboratoire d’Astrophysique de Marseille, 13376 Marseille Cedex 12, FranceA. M. KoekemoerSpace Telescope Science Institute, Baltimore, MD 21218A. LeauthaudLaboratoire d’Astrophysique de Marseille, 13376 Marseille Cedex 12, FranceH. J. McCrackenInstitut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre et Marie Curie, 75014 Paris, FranceTakashi MurayamaAstronomical Institute, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, JapanTohru NagaoAstronomical Institute, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, JapanJason RhodesCalifornia Institute of Technology, MC 105-24, Pasadena, CA 91125D. B. SandersUniversity of Hawaii, Honolulu, HI 96822S. SasakiAstronomical Institute, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, JapanYasuhiro ShioyaAstronomical Institute, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, JapanL. TascaMax-Planck-Institut für Astrophysik, D-85748 Garching bei München, GermanyJames E. TaylorCalifornia Institute of Technology, MC 105-24, Pasadena, CA 91125

2007en

ABI

Аннотация

We have identified a large-scale structure at z~0.73 in the COSMOS field, coherently described by the distribution of galaxy photometric redshifts, an ACS weak-lensing convergence map and the distribution of extended X-ray sources in a mosaic of XMM observations. The main peak seen in these maps corresponds to a rich cluster with Tx= 3.51+0.60/-0.46 keV and Lx=(1.56+/-0.04) x 10^{44} erg/s ([0.1-2.4] keV band). We estimate an X-ray mass within $r500$ corresponding to M500~1.6 x 10^{14} Msun and a total lensing mass (extrapolated by fitting a NFW profile) M(NFW)=(6+/-3) x 10^15 Msun. We use an automated morphological classification of all galaxies brighter than I_AB=24 over the structure area to measure the fraction of early-type objects as a function of local projected density Sigma_10, based on photometric redshifts derived from ground-based deep multi-band photometry. We recover a robust morphology-density relation at this redshift, indicating, for comparable local densities, a smaller fraction of early-type galaxies than today. Interestingly, this difference is less strong at the highest densities and becomes more severe in intermediate environments. We also find, however, local "inversions'' of the observed global relation, possibly driven by the large-scale environment. In particular, we find direct correspondence of a large concentration of disk galaxies to (the colder side of) a possible shock region detected in the X-ray temperature map and surface brightness distribution of the dominant cluster. We interpret this as potential evidence of shock-induced star formation in existing galaxy disks, during the ongoing merger between two sub-clusters.

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DOI: 10.1086/516588

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