• Van Dokkum, Pieter
• Franx, Marijn
• Ellingson, Erica
• Hoekstra, Henk
• Lacy, Mark
• Surace, Jason
• Rettura, Alessandro
• Lidman, Chris
• Webb, Tracy
• Nantais, Julie
• Hicks, Amalia
• Muzzin, Adam
• Wilson, Gillian
• Noble, Allison
• Yee, H. K. C.
• Gilbank, David
• Demarco, Ricardo
• Balogh, Michael

Abstract

We evaluate the effects of environment and stellar mass on galaxy properties at 0.85 〈z 〈 1.20 using a 3.6 μm-selected spectroscopic sample of 797 cluster and field galaxies drawn from the Gemini Cluster Astrophysics Spectroscopic Survey. We confirm that for galaxies with log M <SUB>*</SUB>/M <SUB>☉</SUB> 〉 9.3 the well-known correlations between environment and properties such as star-forming fraction (f <SUB>SF</SUB>), star formation rate (SFR), specific SFR (SSFR), D <SUB> n </SUB>(4000), and color are already in place at z ~ 1. We separate the effects of environment and stellar mass on galaxies by comparing the properties of star-forming and quiescent galaxies at fixed environment and fixed stellar mass. The SSFR of star-forming galaxies at fixed environment is correlated with stellar mass; however, at fixed stellar mass it is independent of environment. The same trend exists for the D <SUB> n </SUB>(4000) measures of both the star-forming and quiescent galaxies and shows that their properties are determined primarily by their stellar mass, not by their environment. Instead, it appears that environment's primary role is to control the fraction of star-forming galaxies. Using the spectra we identify candidate poststarburst galaxies and find that those with 9.3 〈 log M <SUB>*</SUB>/M <SUB>☉</SUB> 〈 10.7 are 3.1 ± 1.1 times more common in high-density regions compared to low-density regions. The clear association of poststarbursts with high-density regions as well as the lack of a correlation between the SSFRs and D <SUB> n </SUB>(4000)s of star-forming galaxies with their environment strongly suggests that at z ~ 1 the environmental-quenching timescale must be rapid. Lastly, we construct a simple quenching model which demonstrates that the lack of a correlation between the D <SUB> n </SUB>(4000) of quiescent galaxies and their environment results naturally if self quenching dominates over environmental quenching at z 〉 1, or if the evolution of the self-quenching rate mirrors the evolution of the environmental-quenching rate at z 〉 1, regardless of which dominates.Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

Topics

• density
• impedance spectroscopy
• cluster
• forming
• quenching