NGC3314a/b and NGC3312: Ram pressure stripping in Hydra I cluster substructure

Cluster substructure and ram pressure stripping in individual galaxies are among the primary pieces of evidence for the ongoing growth of galaxy clusters as they accrete galaxies and groups from their surroundings. We present a multiwavelength study of the center of the Hydra I galaxy cluster, including exquisite new MeerKAT H i and DECam Hff imaging which reveal conclusive evidence for ram pressure stripping in NGC3312, NGC3314a, and NGC3314b through compressed H i contours, well-defined H i tails, and ongoing star formation in the stripped gas. In particular, we quantify the stripped material in NGC3312, and NGC3314a, which makes up between 8% and 35% of the gas still in the disk, is forming stars at similar to 0.5 M(circle dot)yr(-1), and extends similar to 30 60 kpc from the main disk. The estimated stellar mass in the tails is an order of magnitude less than the H i mass. A fourth "ring" galaxy at the same velocity does not show signs of ram pressure in H i. In addition, we used the H i and stellar morphologies, combined with a Beta model of the hot intracluster medium, to constrain the real distances of the galaxies to the cluster center, and we used the chance alignment of NGC3314b behind NGC3314a to break the degeneracy between whether the galaxies are in front or in back of the cluster. The drag seen in the H i tails supports our preferred scenario that NGC3312 and NGC3314a are moving toward us as part of a foreground substructure which has already passed its pericenter and is on "out fall" from the cluster. The high surviving H i content of the galaxies may suggest that the substructure or intragroup medium can protect them from the harshest e ffects of ram pressure, or that the galaxies are in fact on more tangential orbits.