A Comparative Study of Density Field Estimation for Galaxies: New Insights into the Evolution of Galaxies with Environment in COSMOS out to z ~ 3
It is well-known that a galaxy's environment has a fundamental influence in shaping its properties. We study the environmental effects on galaxy evolution, with an emphasis on the environment defined as the local number density of galaxies. The density field is estimated with different estimators (weighted adaptive kernel smoothing, 10th and 5th nearest neighbors, Voronoi and Delaunay tessellation) for a K_s < 24 sample of ~190,000 galaxies in the COSMOS field at 0.1 < z < 3.1. The performance of each estimator is evaluated with extensive simulations. We show that overall there is a good agreement between the estimated density fields using different methods over ~2 dex in overdensity values. However, our simulations show that adaptive kernel and Voronoi tessellation outperform other methods. Using the Voronoi tessellation method, we assign surface densities to a mass complete sample of quiescent and star-forming galaxies out to z ~ 3. We show that at a fixed stellar mass, the median color of quiescent galaxies does not depend on their host environment out to z ~ 3. We find that the number and stellar mass density of massive (>10^11 M_⊙) star-forming galaxies have not significantly changed since z ~ 3, regardless of their environment. However, for massive quiescent systems at lower redshifts (z ≲ 1.3), we find a significant evolution in the number and stellar mass densities in denser environments compared to lower density regions. Our results suggest that the relation between stellar mass and local density is more fundamental than the color–density relation and that environment plays a significant role in quenching star-formation activity in galaxies at z ≲ 1.
© 2015 The American Astronomical Society. Received 2015 January 26; accepted 2015 March 27; published 2015 May 27. We gratefully thank the anonymous referee for thoroughly reading the original manuscript and providing very useful comments that improved the quality of the work. B.D. gratefully acknowledges Lucia Pozzetti for providing the data for this study. D.S. acknowledges financial support from LKBF, the Netherlands Organisation for Scientific research (NWO) through a Veni fellowship, from FCT through an FCT Investigator Starting Grant, a Start-up Grant (IF/01154/2012/CP0189/CT0010), and the grant PEst-OE/FIS/UI2751/2014. This study used the COSMOS data based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555, and the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. It is also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program 175.A-01279, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (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 with MegaPrime/MegaCam operated as a joint project by the CFHT Corporation, CEA/DAPNIA, the NRC and CADC of Canada, the CNRS of France, TERAPIX, and the University of Hawaii.
Published - 0004-637X_805_2_121.pdf
Submitted - 1503.07879v1.pdf