arXiv:0911.4297v1 [astro-ph.CO] 22 Nov 2009 Draft version November 22, 2009 Preprint typeset using L A T E X style emulateapj v. 08/22/09 ENVIRONMENT OF MAMBO GALAXIES IN THE COSMOS FIELD ∗ M. Aravena 1,2,3 , F. Bertoldi 2 , C. Carilli 4 , E. Schinnerer 5 , H. J. McCracken 6 , M. Salvato 7,8,9 , D. Riechers 7,10 , K. Sheth 1 ,V. Smˇ olci´ c 7 , P. Capak 11 , A. M. Koekemoer 12 , K. M. Menten 3 Draft version November 22, 2009 ABSTRACT Submillimeter galaxies (SMG) represent a dust-obscured high-redshift population undergoing mas- sive star formation activity. Their properties and space density have suggested that they may evolve into spheroidal galaxies residing in galaxy clusters. In this paper, we report the discovery of compact (∼ 10 -20 ′′ ) galaxy overdensities centered at the position of three SMGs detected with the Max-Planck Millimeter Bolometer camera (MAMBO) in the COSMOS field. These associations are statistically significant. The photometric redshifts of galaxies in these structures are consistent with their asso- ciated SMGs; all of them are between z =1.4 - 2.5, implying projected physical sizes of ∼ 170 kpc for the overdensities. Our results suggest that about 30% of the radio-identified bright SMGs in that redshift range form in galaxy density peaks in the crucial epoch when most stars formed. Subject headings: galaxies: evolution — galaxies: high-redshift — galaxies: starburst — galaxies: clusters: general 1. INTRODUCTION Submillimeter galaxies (SMG) are dust-obscured starburst galaxies at high-redshift (Smail et al. 1997; Hughes et al. 1998; Barger et al. 1998). Their large dy- namical (Greve et al. 2005; Tacconi et al. 2006, 2008) and stellar masses (Borys et al. 2005; Dye et al. 2008), as well as their number densities and clustering properties (Scott et al. 2002; Blain et al. 2004; Viero et al. 2009), suggest they could be the progenitors of present-day luminous ellipticals (Lilly et al. 1999; Swinbank et al. 2006). Some SMGs are known to be associated with galaxy clusters at high redshifts (e.g. Webb et al. 2005) and to be located in extended overdensities of LBGs and radio galaxy fields (Ivison et al. 2000; Smail et al. 2003; Stevens et al. 2003; Chapman et al. 2008; Daddi et al. 2009; Tamura et al. 2009). If SMGs are progenitors of massive clustered spheroids, ∗ Based on observations obtained, within the COSMOS Legacy Survey, with the IRAM 30 m , NRAO-VLA, HST, CFHT, Subaru, KPNO, CTIO, and ESO Observatories. The National Radio As- tronomy Observatory is a facility of the National Science Founda- tion (NSF), operated under cooperative agreement by Associated Universities Inc. 1 National Radio Astronomy Observatory. 520 Edgemont Road, Charlottesville VA 22903, USA. maravena@nrao.edu 2 Argelander Institut f¨ ur Astronomie. Auf dem H¨ ugel 71, 53121 Bonn, Germany. 3 Max-Planck Institut f¨ ur Radioastronomie. Auf dem H¨ ugel 69, 53121 Bonn, Germany. 4 National Radio Astronomy Observatory. P.O. Box O, Socorro, NM 87801, USA 5 Max-Planck-Institut fr Astronomie. K¨ onigstuhl 17, D-69117 Heidelberg, Germany 6 Institut d’Astrophysique de Paris. 98bis boulevard Arago, 75014 Paris, France 7 California Institute of Technology. 1200 East California Boule- vard, Pasadena, CA 91125, USA 8 Max-Planck Institut f¨ ur Plasmaphysik. Boltzmannstrasse 2, D-85748, Garching, Germany 9 Excellence Cluster Universe, Boltzmannstrasse 2. D-85748, Garching, Germany 10 Hubble fellow 11 Spitzer Science Center, Caltech, Pasadena, CA 91125, USA 12 Space Telescope Science Institute. 3700 San Martin Drive, Baltimore, MD 21218, USA they would likely show signs of clustering in the epoch when these galaxies have their peak in activity and lumi- nosity (z ∼ 1 - 3), similar to what is observed for power- ful AGN (Miley & De Breuck 2008). Attempts to mea- sure the clustering of SMGs indicate that they are asso- ciated with massive dark matter halos and possibly trace the largest scale structures at high redshifts (Blain et al. 2004; Viero et al. 2009; Weiss et al. 2009). However, cur- rent submillimeter blank-field surveys either cover small areas in the sky, yielding a few tens of sources within con- tiguous fields (Coppin et al. 2006; Bertoldi et al. 2007; Scott et al. 2008; Perera et al. 2008; Austermann et al. 2009), or are limited by poor angular resolution albeit covering large regions (Devlin et al. 2009). Hence, good quantitative studies of the small to large scale clustering of the SMG population are not feasible until large sur- veys comprising a few square degrees on the sky under good resolution ( 20 ′′ ) can be made. Studies of the environment of SMGs are possible when utilizing the rich complementary data available for cur- rent (sub)millimeter fields. Whether SMGs are embed- ded in regions with an enhanced number of optical/near- IR detected high-redshift galaxies has yet not been quan- tified. In this paper, we investigate to what extent SMGs are located in clustered fields. For this, we make use of deep optical and near-IR imaging data in the central part of the COSMOS field to measure the density of high- redshift BzK galaxies in the surroundings of SMGs. This allows us to study the relation of blank-field detected SMGs with the most prominent galaxy density peaks at high-redshift. Hereafter, we assume a cosmology with H 0 = 70 km s −1 Mpc −1 ,Ω Λ =0.7 and Ω M =0.3 and use all magnitudes in the AB system. 2. OBSERVATIONS 2.1. COSMOS photometric data The COSMOS survey (Scoville et al. 2007) covers a sufficiently large area ,1.4 ◦ × 1.4 ◦ , at appropriate depth over nearly the entire electromagnetic spectrum to pro- vide a comprehensive view of galaxy formation and large