HST/WFC3 grism observations of z ∼ 1 clusters: the cluster versus field stellar mass–size relation and evidence for size growth of quiescent galaxies from minor mergers. Issue 1 (27th December 2018)

• Record Type: Journal Article
• Authors: Matharu, J; Muzzin, A; Brammer, G B; van der Burg, R F J; Auger, M W; Hewett, P C; van der Wel, A; van Dokkum, P; Balogh, M; Chan, J C C; Demarco, R; Marchesini, D; Nelson, E J; Noble, A; Wilson, G; Yee, H K C
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 484:Issue 1(2019)
• Page Start: 595
• Page End: 617
• Publication Date: 2018-12-27
• Subjects: galaxies: clusters: general -- galaxies: evolution -- galaxies: high-redshift -- galaxies: star formation -- galaxies: stellar content; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty3465
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Minor mergers are thought to be responsible for the size growth of quiescent field galaxies with decreasing redshift. We test this hypothesis using the cluster environment as a laboratory. Satellite galaxies in clusters move at high velocities, making mergers between them rare. The stellar mass–size relation in 10 clusters and in the field is measured and compared at$z$ ∼ 1. Our cluster sample contains 344 spectroscopically confirmed cluster members with Gemini/Gemini Multi-Object Spectrographs and 182 confirmed with Hubble Space Telescope /Wide Field Camera 3 G141 grism spectroscopy. On average, quiescent and star-forming cluster galaxies are smaller than their field counterparts by (0.08 ± 0.04) and (0.07 ± 0.01) dex, respectively. These size offsets are consistent with the average sizes of quiescent and star-forming field galaxies between 1.2 ≤$z$ ≤ 1.5, implying the cluster environment has inhibited size growth between this period and$z$ ∼ 1. The negligible differences measured between the$z$ ∼ 0 field and cluster quiescent mass–size relations in other works imply that the average size of quiescent cluster galaxies must rise with decreasing redshift. Using a toy model, we show that the disappearance of the compact cluster galaxies might be explained if, on average, ${\sim }40{{\ \rm per\ cent}}$ of them merge with their brightest cluster galaxies (BCGs) and${\sim }60{{\ \rm per\ cent}}$ are tidally destroyed into the intracluster light (ICL) between 0 ≤$z$ ≤ 1. This is in agreement with the observed stellar mass growth of BCGs between 0 ≤$z$ ≤ 1 and the observed ICL stellar mass fraction at$z$ ∼ 0. Our results support minor mergers as the cause for the size growth in quiescent field galaxies, with cluster-specific processes responsible for the similarity between the field and cluster quiescent mass–size relations at low redshift.