Gas-Bearing Early-Type Dwarf Galaxies in Virgo: Evidence for Recent Accretion

TL;DR

This study examines gas-rich early-type dwarf galaxies in Virgo, providing evidence that some have recently reaccreted gas, challenging traditional views on galaxy evolution within clusters.

Contribution

It presents new observational evidence of gas reaccretion in early-type dwarf galaxies, suggesting recent accretion events influence their evolution.

Findings

Half of the HI-detected early-type dwarfs are star-forming.

The other half are quiescent but show signs of recent gas reaccretion.

Cluster environment influences the evolutionary pathways of these dwarfs.

Abstract

We investigate the dwarf (M_B> -16) galaxies in the Virgo cluster in the radio, optical, and ultraviolet regimes. Of the 365 galaxies in this sample, 80 have been detected in HI by the Arecibo Legacy Fast ALFA survey. These detections include 12 early-type dwarfs which have HI and stellar masses similar to the cluster dwarf irregulars and BCDs. In this sample of 12, half have star-formation properties similar to late type dwarfs, while the other half are quiescent like typical early-type dwarfs. We also discuss three possible mechanisms for their evolution: that they are infalling field galaxies that have been or are currently being evolved by the cluster, that they are stripped objects whose gas is recycled, and that the observed HI has been recently reaccreted. Evolution by the cluster adequately explains the star-forming half of the sample, but the quiescent class of early-type dwarfs is most consistent with having recently reaccreted their gas.