65 kpc of ionized gas trailing behind NGC 4848 during its first crossing of the Coma cluster

TL;DR

This study reports the discovery of a 65 kpc ionized gas tail behind NGC 4848 in the Coma cluster, indicating ram pressure stripping during its first infall into the cluster environment.

Contribution

The paper provides direct observational evidence of ram pressure stripping in NGC 4848, including detailed morphology and gas mass estimates, supporting models of galaxy evolution in clusters.

Findings

65 kpc ionized gas tail detected behind NGC 4848

Galaxy undergoing ram pressure stripping during first cluster infall

Estimated 4 x 10^9 Msun of gas removed in less than 200 Myr

Abstract

In a 5 hour Halpha exposure of the N-W region of the Coma cluster with the 2.1m telescope at SPM (Mx) we discovered a 65 kpc cometary emission of ionized gas trailing behind the SBab galaxy NGC 4848. The tail points in the opposite direction of the cluster center, in the same direction where stripped HI has been detected in previous observations. The galaxy shows bright HII regions in an inner ring-like pattern, where the star formation takes place at the prodigious rate of 8.9 Msun/yr. From the morphology of the galaxy and of the trailing material, we infer that the galaxy is suffering from ram pressure due to its high velocity motion through the cluster IGM. We estimate that 4 x 10^9 Msun of gas is swept out from the galaxy forming the tail. Given the ambient conditions in the Coma cluster (rho = 6.3 x 10^-27 g/cm^3; sigma_vel = 940 km/s) simulations predict that the ram pressure mechanism is able to remove such an amount of gas in less than 200 Myr. This, combined with the geometry of the interaction, indicating radial infall into the cluster, leads to the conclusion that NGC 4848 is caught in its first passage through the dense cluster environment.