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

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 (µ r ∼ 27 mag arcsec −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.

Galaxy and mass assembly: luminosity and stellar mass functions in GAMA groups

“…), comparable to what is found in low-density field environments (van Dokkum 2005). Oh et al (2018) find that 20 per cent of galaxies observed in rich clusters show post-merger signatures, whereas only 4 per cent show evidence of ongoing mergers, in agreement with Sheen et al (2012). Oh et al (2018) suggest that the mergers took place before galaxy accretion into the cluster environment, a claim supported by the numerical simulations of Yi et al (2013).…”

Physical properties of the X-ray gas as a dynamical diagnosis for galaxy clusters

“…Our temperature map does not show such high values, since kT ranges from ∼ 4.0 keV up to 7.0 keV. Using the KASI-Yonsei Deep Imaging Survey of Clusters (KYDISC), Oh et al (2018) found more than 400 spectroscopic members, and the redshift histogram is well fit by a gaussian distribution, showing no evidence of merging. What calls our attention is the higher temperature "ring" in the center, which is associated with AGNs, although we found no indication for this in the literature.…”

Discovering the most elusive radio relic in the sky: diffuse shock acceleration caught in the act?

“…Laganá et al (2019) provided detailed XMM-Newton maps of temperature (peaking in the 4-7 keV energy band), pseudopressure, pseudo-entropy, and metallicity in the central region, within the first ∼400 kpc from the cluster centre. They classified A2249 as a non-cool-core disturbed cluster, although Oh et al (2018) and Lopes et al (2018) did not find evidence for merging from the spectroscopic redshift distribution of cluster members. However, a Dressler and Shectman three-dimensional test of the galaxy redshifts suggests that the cluster is disturbed (Lopes et al 2018).…”

“…In this work, we present the discovery of a giant radio relic found at the periphery of the galaxy cluster Abell 2249 (hereafter A2249; RA 257.44080, Dec. 34.45566). Its galaxies and ICM features have been studied in detail at various wavelengths by a number of authors: the cluster mean redshift is z = 0.0838 (Bulbul et al 2016;Lopes et al 2018;Laganá, Durret & Lopes 2019); the velocity dispersion of its constituent galaxies is between σ vel = 894 ± 50 (Lopes et al 2018) and 976 ± 38 km s −1 (Oh et al 2018). Laganá et al (2019) provided detailed XMM-Newton maps of temperature (peaking in the 4-7 keV energy band), pseudopressure, pseudo-entropy, and metallicity in the central region, within the first ∼400 kpc from the cluster centre.…”

“…The radius of the cluster is R 500 = 1.56 ± 0.06, 1.1 +0.3 −0.1 Mpc depending on the mass estimate, which is debated between the values M 500 = 11.7 ± 1.4, 4.0 +5.2 −1.1 , and 3.73 +0.18 −0.19 , in units of 10 14 M , derived from radial velocity distribution, Chandra and Planck data, respectively (Planck Collaboration XXVII 2016; Zhu et al 2016;Lopes et al 2018). At larger radii, R 200 = 2.2 ± 0.1 Mpc and M 200 = 12.7 ± 1.5 × 10 14 M (Lopes et al 2018;Oh et al 2018).…”