KYDISC: Galaxy Morphology, Quenching, and Mergers in the Cluster Environment

TL;DR

This study uses deep imaging to analyze galaxy morphology, quenching, and mergers in 14 galaxy clusters, revealing environmental effects and a high recent merger rate that predates cluster accretion.

Contribution

It provides a comprehensive catalog of cluster galaxies and uncovers new insights into the relationship between galaxy properties and cluster environment, especially regarding mergers and quenching.

Findings

Morphological content correlates with cluster velocity dispersion.

Passive spirals are concentrated in dense cluster centers.

20% of galaxies show signs of recent mergers, higher than theoretical expectations.

Abstract

We present the KASI-Yonsei Deep Imaging Survey of Clusters (KYDISC) targeting 14 clusters at 0.015 < z < 0.144 using the Inamori Magellan Areal Camera and Spectrograph on the 6.5-meter Magellan Baade telescope and the MegaCam on the 3.6-meter Canada-France-Hawaii Telescope. We provide a catalog of cluster galaxies that lists magnitudes, redshifts, morphologies, bulge-to-total ratios, and local density. Based on the 1409 spectroscopically-confirmed cluster galaxies brighter than -19.8 in the r-band, we study galaxy morphology, color, and visual features generated by galaxy mergers. We see a clear trend between morphological content and cluster velocity dispersion, which was not presented by previous studies using local clusters. Passive spirals are preferentially found in a highly dense region (i.e., cluster center), indicating that they have gone through the environmental quenching. In deep images (mu_r ~ 27 mag/"^2), 20% of our sample show signatures of recent mergers, which is not expected from theoretical predictions and a low frequency of ongoing mergers in our sample (~ 4%). Such a high fraction of recent mergers in the cluster environment supports a scenario that the merger events that made the features have preceded the galaxy accretion into the cluster environment. We conclude that mergers affect a cluster population mainly through the pre-processing on recently accreted galaxies.