Ubiquitous ram pressure stripping in the Coma cluster of galaxies

TL;DR

This study reports the detection of Hα trails behind three galaxies in the Coma cluster, providing evidence of ram pressure stripping, and highlights that 63% of late-type galaxies show direct signs of this process.

Contribution

It presents new observations of Hα trails in three galaxies, expanding the known cases of ram pressure stripping in the Coma cluster, and analyzes their kinematic properties.

Findings

Detected 3 new Hα trails indicating ram pressure stripping.

Found 17 out of 27 late-type galaxies show extended ionized gas tails.

Late-type galaxies with Hα tails have distinct kinematic properties.

Abstract

We report the detection of H$\alpha$ trails behind three new intermediate-mass irregular galaxies in the NW outskirts of the nearby cluster of galaxies Abell 1656 (Coma). Hints that these galaxies possess an extended component were found in earlier, deeper H$\alpha$ observations carried out with the Subaru telescope. However the lack of a simultaneous $r$-band exposure, together with the presence of strong stellar ghosts in the Subaru images, prevented us from quantifying the detections. We therefore devoted one full night of H$\alpha$ observation to each of the three galaxies using the San Pedro Martir 2.1m telescope. One-sided tails of H$\alpha$ emission of 10-20 kpc projected size were detected, suggesting an ongoing ram pressure stripping event. We added these 3 new sources of extended ionized gas (EIG) added to the 12 found by Yagi et al. (2010), NGC 4848 (Fossati et al. 2012), and NGC 4921 whose ram pressure stripping is certified by HI asymmetry. This brings the number sources with H$\alpha$ trails to 17 gaseous tails out of 27 (63 \%) late-type galaxies (LTG) galaxies members of the Coma cluster with direct evidence of ram pressure stripping. The 27 LTG galaxies, among these the 17 with extended H$\alpha$ tails, have kinematic properties that are different from the rest of the early-type galaxy (ETG) population of the c ore of the Coma cluster, as they deviate in the phase-space diagram $\Delta$V/$\sigma$ versus $r/R_{200}$.