The Angular Correlations of Galaxies in the COSMOS Field

Creators: McCracken, H. J.; Peacock, J. A.; Guzzo, L.; Capak, P.; Porciani, C.; Scoville, N.; Aussel, H.; Finoguenov, A.; James, J. B.; Kitzbichler, M. G.; Koekemoer, A.; Leauthaud, A.; Le Fèvre, O.; Massey, R.; Mellier, Y.; Mobasher, B.; Norberg, P.; Rhodes, J.; Sanders, D. B.; Sasaki, S. S.; Taniguchi, Y.; Thompson, D. J.; White, S. D. M.; El-Zant, A.

Abstract

We present measurements of the two-point galaxy angular correlation function w(θ) in the COSMOS field. Independent determinations of w(θ) as a function of magnitude limit are presented for both the Hubble Space Telescope (HST) ACS catalog and also the ground-based data from Subaru and the Canada-France-Hawaii Telescope. Despite having significantly different masks, these three determinations agree well. At bright magnitudes (I_(AB) < 22), our data generally match very well with existing measurements and with mock catalogs based on the semianalytic galaxy formation calculations of Kitzbichler & White (2007) from the Millennium Simulation. The exception is that our result is at the upper end of the expected cosmic variance scatter for θ > 10', which we attribute to a particularly rich structure known to exist at z ≃ 0.8. For fainter samples, however, the level of clustering is somewhat higher than reported by some previous studies; in all three catalogs we find w(θ = 1') ≃ 0.014 at a median I_(AB) magnitude of 24. At these very faintest magnitudes, our measurements agree well with the latest determinations from the Canada-France Legacy Survey. This level of clustering is approximately double what is predicted by the semianalytic catalogs (at all angles). The semianalytic results allow an estimate of cosmic variance, which is too small to account for the discrepancy. We therefore conclude that the mean amplitude of clustering at this level is higher than previously estimated.

Additional Information

© 2007 American Astronomical Society. Received 2006 November 10; accepted 2007 April 3. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555; also based on data collected at: the Subaru Telescope, which is operated by The National Astronomical Observatory of Japan; the XMM-Newton, an ESA science Mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by AURA under cooperative agreement with the National Science Foundation; the National Radio Astronomy Observatory, which is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.; and the Canada-France-Hawaii Telescope (CFHT) with MegaPrime/MegaCam, operated as a joint project by the CFHT Corporation, CEA/DAPNIA, the National Research Council of Canada, the Canadian Astronomy Data Centre, the Centre National de la Recherche Scientifique de France, TERAPIX, and the University of Hawaii. The HST COSMOS Treasury program was supported through NASA grant HST-GO-09822. We wish to thank Tony Roman, Denise Taylor, and David Soderblom for their assistance in planning and scheduling the extensive COSMOS observations. We gratefully acknowledge the contributions of the entire COSMOS collaboration, consisting of more than 70 scientists. More information on the COSMOS survey is available at http://www.astro.caltech.edu/~cosmos. It is a pleasure to acknowledge the excellent services provided by the NASA IPAC/IRSA staff (Anastasia Laity, Anastasia Alexov, Bruce Berriman, and John Good) in providing online archive and server capabilities for the COSMOS data sets.

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