Large Molecular Gas Reservoirs in Star-forming Cluster Galaxies

Abstract

We present CO(2-1) observations of 72 galaxies in the nearby, disturbed Antlia galaxy cluster with the Atacama Pathfinder Experiment (APEX) telescope. The galaxies in our sample are selected to span a wide range of stellar masses (10 8 M M 10 10 M ) and star formation rates (0.0005 M yr −1 < SFR < 0.3 M yr −1 ). Reaching a depth of 23 mJy in 50 km s −1 channels, we report a total CO detection rate of 37.5% and a CO detection rate of 86% for sources within 1 dex of the main sequence. We compare our sample with a similar sample of galaxies in the field, finding that, for a fixed stellar mass and SFR, galaxies in the Antlia cluster have comparable molecular gas reservoirs to field galaxies. We find that ∼ 41% (11/27) of our CO detections display non-Gaussian CO(2-1) emission line profiles, and a number of these sources display evidence of quenching in their optical images. We also find that the majority of our sample lie either just below, or far below the main sequence of field galaxies, further hinting at potential ongoing quenching. We conclude that the Antlia cluster represents an intermediate environment between fields and dense clusters, where the gentler intracluster medium (ICM) allows the cluster members to retain their reservoirs of molecular gas, but in which the disturbed ICM is just beginning to influence the member galaxies, resulting in high SFRs and possible ongoing quenching.

Star Formation Enhancement in Barred Disk Galaxies in Interacting Galaxy Clusters

“…This could be also attributed to the bar-driven enhancement of star formation. However, in non-interacting clusters, the bar formation is 17 Several previous studies show that some galaxies in clusters in merging processes or with substructures can have large amounts of H I gas or molecular gas contents that are comparable to field galaxies Cybulski et al 2016;Cairns et al 2019). likely not due to a cluster-wide mechanism occurring in a narrow time period as in the case of interacting clusters. Therefore, a number of bars formed recently (and subsequent star-formation activities triggered recently) would be smaller in non-interacting clusters than in interacting clusters.…”

“…This could be also attributed to the bar-driven enhancement of star formation. However, in non-interacting clusters, the bar formation is 17 Several previous studies show that some galaxies in clusters in merging processes or with substructures can have large amounts of H I gas or molecular gas contents that are comparable to field galaxies (Stroe et al 2015;Cybulski et al 2016;Cairns et al 2019).…”

ENISALA. II. Distinct Star Formation and Active Galactic Nucleus Activity in Merging and Relaxed Galaxy Clusters

“…Cohen et al 2014;Yoon & Im 2020) and blue galaxies (e.g. Wang et al 1997;Cortese et al 2004;Hou et al 2012;Cava et al 2017) and are more gas-rich than counterparts in relaxed clusters (Stroe et al 2015a;Jaffé et al 2012Jaffé et al , 2016Cairns et al 2019). There is also compelling evidence from multiwavelength data that cluster mergers trigger AGN activity (Miller & Owen 2003;Owen et al 1999;Sobral et al 2015;Hwang & Lee 2009).…”

The First Integral Field Unit Spectroscopic View of Shocked Cluster Galaxies

“…Andrade-Santos et al 2017;Rossetti et al 2017) and of particular interest to the community as they present some surprising reversals of the typical environmental trends found in relaxed clusters. Studies contrasting statistical samples of relaxed and merging clusters, found that merging galaxy clusters have a higher density of emission-line, star-forming and blue galaxies, with higher specific SF rates (sSFR), stronger barred morphological features and large gas reservoirs and a higher fraction of active galactic nuclei (AGN) (Miller & Owen 2003;Cortese et al 2004;Hwang & Lee 2009;Hou et al 2012;Jaffé et al 2012Jaffé et al , 2016Sobral et al 2015;Stroe et al 2015b,a;Stroe et al 2017;Cairns et al 2019;Yoon et al 2019;Yoon & Im 2020).…”