The Arecibo Galaxy Environment Survey VI : The Virgo Cluster (II)

TL;DR

This study uses 21 cm observations of the Virgo cluster to analyze galaxy distribution, HI mass function, and evidence of ongoing assembly and gas loss processes, revealing differences between cluster and background galaxies.

Contribution

It provides new HI mass function data and insights into galaxy evolution and gas stripping in the Virgo cluster using combined observational datasets.

Findings

Higher detection rate at low HI masses compared to wider surveys

Spatial and velocity distribution differences indicate ongoing cluster assembly

Evidence of ram pressure stripping affecting galaxy gas content

Abstract

We present 21 cm observations of a 5 x degree region in the Virgo cluster, obtained as part of the Arecibo Galaxy Environment Survey. 13 cluster members are detected, together with 36 objects in the background. We compare and contrast the results from this area with a larger 10 x degree region. We combine the two data sets to produce an HI mass function, which shows a higher detection rate at low masses (but finds fewer massive galaxies) than less sensitive wider-area surveys, such as ALFALFA. We find that the HI-detected galaxies are distributed differently to the non-detections, both spatially and in velocity, providing further evidence that the cluster is still assembling. We use the Tully-Fisher relation to examine the possibility of morphological evolution. We find that highly deficient galaxies, as well as some early-type galaxies, have much lower velocity widths than the Tully-Fisher relation predicts, indicating gas loss via ram pressure stripping. We also find that HI detections without optical counterparts do not fit the predictions of the baryonic Tully-Fisher relation, implying that they are not primordial objects.