The Arecibo Galaxy Environment Survey V : The Virgo Cluster (I)

TL;DR

This study presents 21 cm observations of the Virgo cluster, detecting 289 sources, including new faint objects, and analyzes their optical counterparts and gas content, revealing differences between cluster and field galaxies.

Contribution

First comprehensive HI survey of the Virgo cluster combining Arecibo data with optical and SDSS data, identifying new faint sources and analyzing gas content in cluster galaxies.

Findings

289 sources detected, 95 in the cluster

30% of detections are new, faint objects

Cluster galaxies undetected in HI are gas-depleted

Abstract

We present 21 cm observations of a 10 $\times$ 2 degree region in the Virgo cluster, obtained as part of the Arecibo Galaxy Environment Survey. 289 sources are detected over the full redshift range (-2,000 $<$ $v$$_{hel}$ $<$ + 20,000 km/s) with 95 belonging to the cluster ($v$$_{hel}$ $<$ 3,000 km/s). We combine our observations with data from the optically selected Virgo Cluster Catalogue (VCC) and the Sloan Digital Sky Survey (SDSS). Most of our detections can be clearly associated with a unique optical counterpart, and 30% of the cluster detections are new objects fainter than the VCC optical completeness limit. 7 detections may have no optical counterpart and we discuss the possible origins of these objects. 7 detections appear associated with early-type galaxies. We perform HI stacking on the HI-undetected galaxies listed in the VCC in this region and show that they must have significantly less gas than those actually detected in HI. Galaxies undetected in HI in the cluster appear to be really devoid of gas, in contrast to a sample of field galaxies from ALFALFA.