Abstract
ABSTRACT We present results on the environmental dependence of the star-forming galaxy main sequence in 11 galaxy cluster fields at 1.0 < z < 1.5 from the Gemini Observations of Galaxies in Rich Early Environments Survey (GOGREEN) survey. We use a homogeneously selected sample of field and cluster galaxies whose membership is derived from dynamical analysis. Using [$\rm{O{\small II}}$]-derived star formation rates (SFRs), we find that cluster galaxies have suppressed SFRs at fixed stellar mass in comparison to their field counterparts by a factor of 1.4 ± 0.1 (∼3.3σ) across the stellar mass range: 9.0 < log (M*/M⊙) < 11.2. We also find that this modest suppression in the cluster galaxy star-forming main sequence is mass and redshift dependent: the difference between cluster and field increases towards lower stellar masses and lower redshift. When comparing the distribution of cluster and field galaxy SFRs to the star-forming main sequence, we find an overall shift towards lower SFRs in the cluster population, and note the absence of a tail of high SFR galaxies as seen in the field. Given this observed suppression in the cluster galaxy star-forming main sequence, we explore the implications for several scenarios such as formation time differences between cluster and field galaxies, and environmentally induced star formation quenching and associated time-scales.
Highlights
Measurements of the galaxy stellar mass function and cosmic star formation rate (SFR) as a function of redshift have demonstrated that the global star formation activity of galaxies peaked at z ∼ 2, declining until the present day (e.g. Madau & Dickinson 2014 and references therein)
We show the mean star formation rates (SFRs) of cluster and field galaxies in bins of stellar mass where bin widths are chosen adaptively to maintain a similar number of objects in each stellar mass bin
We identify a modest environmental dependence on the star-forming galaxy main sequence: cluster galaxy SFRs are lower than their counterparts in the field at fixed stellar mass
Summary
Measurements of the galaxy stellar mass function and cosmic star formation rate (SFR) as a function of redshift have demonstrated that the global star formation activity of galaxies peaked at z ∼ 2, declining until the present day (e.g. Madau & Dickinson 2014 and references therein). Kauffmann et al 2004; Balogh et al 2004a; Poggianti et al 2006; Cooper et al 2006, 2007; Kimm et al 2009; von der Linden et al 2010; Peng et al 2010; Muzzin et al 2012; Mok et al 2013; Davies et al 2016; Guglielmo et al 2019; Pintos-Castro et al 2019) One explanation for this trend is that galaxies in groups and clusters are subject to additional processes that enhance the quenching rate The bimodality in the galaxy colour and SFR distribution (e.g. Strateva et al 2001; Baldry et al 2004; Balogh et al 2004b; Cassata et al 2008; Wetzel et al 2012; Taylor et al 2015) suggests that these transition galaxies are rare, implying a rapid transformation from the starforming to quiescent population Identifying these transition galaxies from their lower-than-average SFRs requires large, carefully-selected samples over a wide stellar mass range, and results to-date are mixed. Several studies have claimed little to no trend in the star-forming main sequence with environment (e.g. Peng et al 2010; Wijesinghe et al 2012; Muzzin et al 2012; Wetzel et al 2012; Koyama et al 2013); others find a modest trend in the sense that star-forming galaxies in denser environments have lower star formation rates at fixed stellar mass than that of their counterparts in the field (e.g. Vulcani et al 2010; von der Linden et al 2010; Popesso et al 2011; Patel et al 2011; Haines et al 2013; Paccagnella et al 2016; Rodrıguez del Pino et al 2017; Wang et al 2018)
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