Abstract
We analyse the structure of galaxies with high specific star formation rate (SSFR) in cluster and field environments in the redshift range $0.5<z<1.0$. Recent studies have shown that these galaxies are strongly depleted in dense environments due to rapid environmental quenching, giving rise to post-starburst galaxies (PSBs). We use effective radii and S\'ersic indices as tracers of galaxy structure, determined using imaging from the UKIDSS Ultra Deep Survey (UDS). We find that the high-SSFR galaxies that survive into the cluster environment have, on average, larger effective radii than those in the field. We suggest that this trend is likely to be driven by the most compact star-forming galaxies being preferentially quenched in dense environments. We also show that the PSBs in clusters have stellar masses and effective radii that are similar to the missing compact star-forming population, suggesting that these PSBs are the result of size-dependent quenching. We propose that both strong stellar feedback and the stripping of the extended halo act together to preferentially and rapidly quench the compact and low-mass star-forming systems in clusters to produce PSBs. We test this scenario using the stacked spectra of 124 high-SSFR galaxies, showing that more compact galaxies are more likely to host outflows. We conclude that a combination of environmental and secular processes is the most likely explanation for the appearance of PSBs in galaxy clusters.
Highlights
In the local Universe the most massive galaxies are passive and elliptical, while low-mass galaxies tend to be star-forming and have disc-dominated morphologies
3.1 Galaxy size as a function of specific star formation rate In Fig. 2 we show the dependence of the median Re on SSFR for the star-forming galaxies in our sample
Using K-band structural parameters available for the Ultra Deep Survey (UDS), we find that high-SSFR galaxies in clusters are typically larger than analogous galaxies in the field
Summary
In the local Universe the most massive galaxies are passive and elliptical, while low-mass galaxies tend to be star-forming and have disc-dominated morphologies. The observed number of quenched low-mass galaxies increases towards the present day (Drory et al 2009; Baldry et al 2012; Moutard et al 2016, 2018). This downsizing in the passive population is generally associated with environmental quenching, and has been measured up to z ∼ 1 (Muzzin et al 2013; Tomczak et al 2014; Socolovsky et al 2018). These evolutionary trends are consistent with galaxies in high-density. Alternative mechanisms invoke galaxygalaxy interactions, such as mergers, harassment or tidal stripping (Moore et al 1996; Toomre & Toomre 1972; Faber 1973), which are examples of other processes typically associated with high and intermediate-density environments
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