A VLA SURVEY OF THE HERCULES CLUSTER .1. THE H-I DATA

This paper presents results from a survey of lambda 21-cm emission fro m galaxies in the Hercules Cluster, A2151 and A2147. Four VLA primary beam areas were covered, a total area of 0.9 square degrees, including some 120 spiral galaxies brighter than 17.5(m). The velocity resoluti on is 44 km s(-1), the angular resolution 25 ''. The detection thresho ld at field center is 2.6 X 10(8)h(-2) M. in H I mass or about 1.8 X 1 0(20) cm(-2) in column density. There are 61 galaxies detected in H I, of which about 25 had been previously detected at lambda 21-cm. About ten of the detections correspond to galaxies that are very faint in t he optical, m(E) greater than or equal to 18 or M greater than or equa l to-17(m)-5 log h. Some of these low surface brightness galaxies have very extended H I disks, with r greater than or equal to 15 kpc. The abundance of H I is a strong function of position in the cluster, with galaxies in the south and west showing hardly any gas, and galaxies i n the north and east of A2151 frequently having massive, extended gas disks. The morphology of the remnants of gas in galaxies in the south and west suggests that the intracluster medium is responsible for thei r H I deficiency, but there are also several dramatic galaxy mergers i n progress. (C) 1997 American Astronomical Society.