Ubiquitous ram pressure stripping in the Coma cluster of galaxies
  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 $r/R_{200}$.
