HI Clouds detected towards Virgo with the Arecibo Legacy Fast ALFA Survey

TL;DR

The ALFALFA survey detects various HI clouds in Virgo, revealing objects with unique properties, some linked to optical counterparts and others potentially tidal or optically dark, expanding understanding of galaxy environments.

Contribution

This study presents new HI detections in Virgo, including optically dark clouds and tidal features, with follow-up VLA observations providing detailed insights.

Findings

Detection of HI clouds with and without optical counterparts

Identification of potential tidal HI features

Discovery of optically dark HI clouds

Abstract

The Arecibo Legacy Fast ALFA survey is in the process of yielding a complete HI dataset of the Virgo Cluster and its environs (Giovanelli et al. 2007, Kent et al., in preparation). Assuming a distance to Virgo of 16.7 Mpc, the minimum detectable HI mass by ALFALFA is of order 2 x 10^7 Msun. A number of the HI detections appear to have interesting properties. Some appear associated with, but offset from, low surface brightness optical counterparts; others, at larger spatial offsets, may be tidally related to optical counterparts. Yet another class includes detections which are not identifiable with any optical counterparts. We present the ALFALFA results on these objects in the Virgo region, as well as followup aperture synthesis observations obtained with the VLA.