The consequences of ram pressure stripping on the Virgo cluster spiral galaxy NGC 4522

TL;DR

This study uses new H-alpha observations and numerical modeling to demonstrate that ram pressure stripping caused the gas and star formation features observed in the Virgo galaxy NGC 4522, revealing the galaxy's recent interaction history.

Contribution

It provides a detailed analysis combining observations and models to confirm ram pressure stripping as the cause of gas deficiency and disturbed features in NGC 4522.

Findings

Ram pressure stripping caused HI deficiency and disturbed gas distribution.

Re-accretion of gas clouds explains recent star formation.

Gas at >60'' forms an asymmetric expanding ring, partly above the disk plane.

Abstract

New H-alpha Fabry-Perot interferometer observations of the Virgo cluster spiral galaxy NGC 4522 are presented. A velocity field up to a radius of 60'' was obtained. The observed rotation curve is symmetric. It is not perturbed in the inner disk. For radii >50'' it shows a solid body rotation. We compare these data with a numerical model which includes the effects of ram pressure stripping. The model can reproduce the main characteristics of the H-alpha emission distribution and velocity field. We therefore conclude that the stripping event which caused the HI deficiency and the distorted H-alpha distribution and velocity field has been due to ram pressure. The closest passage of the galaxy to the cluster center is estimated to be approx. 6.5 10^8 yr ago. The observed recent star formation is due to the re-accretion of gas clouds which were accelerated to velocities below the escape velocity during the stripping event. Furthermore, the gas which is located at radii >60'' is part of an asymmetric expanding ring of gas clouds. A substantial part of these clouds is located above the disk plane. We predict the HI gas distribution and velocity field as it would be observed by deep 21 cm observations.