Clouds toward the Virgo cluster periphery: gas-rich optically inert galaxies.
Abstract (from CDS):
Aperture synthesis observations of two H I cloud complexes located in the periphery of the Virgo galaxy cluster are presented. These low H I-mass clouds (M_ H I_< 109 M☉) are seen projected on the M region of the western Virgo cluster, where the galaxy population is thought to lie behind the main A cluster surrounding M87. The kinematic measurements of both unresolved Arecibo and resolved Very Large Array (VLA)-C observations are in good agreement. The H I detections cannot be identified with any optical, IR, or UV emission from available archival imaging. They are inert at these wavelengths. The H I masses of the individual VLA detections range from 7.28 ≤ log(M_ H I/M☉_) ≤ 7.85. The total dynamical mass estimates are several times their H I content, ranging from 7.00 ≤ log(Mdyn/M☉) ≤ 9.07, with the assumption that the clouds are self-gravitating and in dynamical equilibrium. We report the observed parameters derived from the VLA observations. One of these H I clouds appears to be the most isolated optically inert detection observed in the outer reaches of Virgo.
galaxies: clusters: individual: Virgo - galaxies: clusters: intracluster medium - galaxies: halos - intergalactic medium - radio lines: galaxies