Glimpsing the imprint of local environment on the galaxy stellar mass function

MNRAS 472, 3512–3531 (2017) doi:10.1093/mnras/stx2245 Advance Access publication 2017 September 4 Glimpsing the imprint of local environment on the galaxy stellar mass function Adam R. Tomczak,1‹ Brian C. Lemaux,1 Lori M. Lubin,1 Roy R. Gal,2 Po-Feng Wu,2,3 Bradford Holden,4 Dale D. Kocevski,5 Simona Mei,6,7,8 Debora Pelliccia,1 Nicholas Rumbaugh9 and Lu Shen1 1 Department of Physics, University of California, Davis, One Shields Ave., Davis, CA 95616, USA of Hawai‘i, Institute for Astronomy, 2680 Woodlawn Drive, HI 96822, USA 3 Max-Planck Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany 4 UCO Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA 5 Department of Physics and Astronomy, Colby College, Waterville, ME 04901, USA 6 LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University Paris 06, F-75014 Paris, France 7 University of Paris Denis Diderot, University of Paris Sorbonne Cité (PSC), F-75205 Paris Cedex 13, France 8 Jet Propulsion Laboratory, Cahill Center for Astronomy & Astrophysics, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA 9 National Center for Supercomputing Applications, University of Illinois, 1205 West Clark St., Urbana, IL 61801, USA 2 University ABSTRACT We investigate the impact of local environment on the galaxy stellar mass function (SMF) spanning a wide range of galaxy densities from the field up to dense cores of massive galaxy clusters. Data are drawn from a sample of eight fields from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey. Deep photometry allow us to select mass-complete samples of galaxies down to 109 M . Taking advantage of >4000 secure spectroscopic redshifts from ORELSE and precise photometric redshifts, we construct threedimensional density maps between 0.55 < z < 1.3 using a Voronoi tessellation approach. We find that the shape of the SMF depends strongly on local environment exhibited by a smooth, continual increase in the relative numbers of high- to low-mass galaxies towards denser environments. A straightforward implication is that local environment proportionally increases the efficiency of (a) destroying lower mass galaxies and/or (b) growth of higher mass galaxies. We also find a presence of this environmental dependence in the SMFs of starforming and quiescent galaxies, although not quite as strongly for the quiescent subsample. To characterize the connection between the SMF of field galaxies and that of denser environments, we devise a simple semi-empirical model. The model begins with a sample of ≈106 galaxies at zstart = 5 with stellar masses distributed according to the field. Simulated galaxies then evolve down to zfinal = 0.8 following empirical prescriptions for star-formation, quenching and galaxy–galaxy merging. We run the simulation multiple times, testing a variety of scenarios with differing overall amounts of merging. Our model suggests that a large number of mergers are required to reproduce the SMF in dense environments. Additionally, a large majority of these mergers would have to occur in intermediate density environments (e.g. galaxy groups). Key words: techniques: photometric – techniques: spectroscopic – galaxies: general – galaxies: evolution – galaxies: groups: general. 1 I N T RO D U C T I O N It has been broadly understood from early observations that galaxies in clusters evolve along different time-scales and/or pathways  E-mail: clusters: relative to those in more isolated environments (e.g. Gunn & Gott 1972; Oemler 1974; Dressler 1980). A variety of mechanisms either unique to or facilitated in cluster environments have been proposed as a means of contextualizing these observations such as ram-pressure stripping (Gunn & Gott 1972) and gravitational interactions between galaxies (Richstone 1976) and with the cluster potential (Farouki & Shapiro 1981). In more recent years, the Sloan  C 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society Accepted 2017 August 25. Received 2017 August 25; in original form 2017 May 5 Imprint of local environment on the galaxy SMF scheme to measurements of the SMF at 0.5  z  1 finding mild to moderate levels of tension (van der Burg et al. 2013; Davidzon et al. 2016). In the latter of these two studies, the authors argue that galaxy–galaxy mergers should also play a significant role in shaping the SMF in high-density environments. In fact, it has been estimated that the merger rate can be 3–4× greater in high- versus low-density environments (Lin et al. 2010; Kampczyk et al. 2013) and exhibits evolution with redshift (López-Sanjuan et al. 2013). It is important to note that the high-density regime examined in these studies combine both galaxy group and galaxy cluster scales, and are more heavily weighted towards group-like environments. Indeed galaxy groups are believed to be the environment most conducive to galaxy–galaxy merging due to their moderate velocity dispersions, whereas velocities in clusters may act to suppress merging despite bolstering elevated number densities of galaxies (Lin et al. 2010). In this paper, we present new measurements of the galaxy SMF as a function of local environment from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey (Lubin et al. 2009). ORELSE is a wide-field survey dedicated to studying galaxy evolution across the full range of local environments with extensive photometric and spectroscopic observations of multiple well-known galaxy overdensities at 0.6 < z < 1.3. In the work presented here, we make use of a subset of eight ORELSE fields from the full sample for which all data have been currently reduced. Nevertheless, this subset covers essentially the entire redshift range of the survey and samples the full range of substructure masses from low-mass groups to rich clusters. This paper is organized as follows. In Section 2, we discuss the photometric and spectroscopic data as well as SED-fitting techniques used to derive galaxy properties. Section 3 describes the various analysis methodologies employed such as the quantitative definition of local environment and the estimation of mass completeness. In Section 4, we discuss the results from our measurements and introduce a simple semi-empirical model as an aid in understanding the connection between the SMF in different environments. Finally, in Section 5, we summarize our results and consider a future direction for a follow-up study. Throughout this paper, we adopt a standard  cold dark matter cosmology with M = 0.3,  = 0.7 and H0 = 70 km s−1 Mpc−1 . 2 DATA In this study, we make use of several fields taken from the ORELSE survey (Lubin et al. 2009). ORELSE is a large multiwavelength photometric and spectroscopic campaign of 161 fields, each containing massive large-scale struc (...truncated)