VLA H [CLC][CSC]i[/CSC][/CLC] Imaging of the Brightest Spiral Galaxies in Coma

Abstract

We have obtained 21 cm images of 19 spiral galaxies in the Coma cluster, using the VLA in its C and D configurations. The sample selection was based on morphology, brightness, and optical diameters of galaxies within one Abell radius (12). The H I?detected, yet deficient galaxies show a strong correlation in their H I properties with projected distance from the cluster center. The most strongly H I?deficient (Def > 0.4) galaxies are located inside a radius of 30' (~0.6 Mpc) from the center of Coma, roughly the extent of the central X-ray emission. These central galaxies show clear asymmetries in their H I distribution and/or shifts between the optical and 21 cm positions. Another 12 spirals were not detected in H I with typical H I mass upper limits of 108 M?. Seven of the 12 nondetections are located in the central region of Coma, roughly within 30' from the center. The other nondetections are to the east and southwest of the center. We looked for seven so-called blue disk galaxies in Coma in H I and detected six. These galaxies are relatively close to the central region of Coma. The nondetected one is the closest to the center. The six detected blue galaxies are mildly H I deficient. We did a more sensitive search for H I from 11 of the 15 known poststarburst galaxies in Coma. None were detected with typical H I mass limits between 3 and 7 ? 107 M?. Our results present and enhance a picture already familiar for well-studied clusters. H I poor galaxies (deficient ones and nondetections) are concentrated toward the center of the cluster. The H I morphology of the central galaxies with optical disks extending beyond the H I disks is unique to cluster environments and strongly suggests an interaction with the intergalactic medium (IGM). A new result in Coma is the clumpy distribution of gas deficiency. In the cluster center the deficient galaxies are to the east while the nondetections are to the west. In the outer parts the gas rich galaxies are north of Coma, nondetected spirals are found in the NGC 4944 group to the east, and the NGC 4839 group is to the southwest. This supports recent findings that merging of groups is ongoing in the center of Coma, farther out the NGC 4944 and NGC 4839 must have passed at least once through the core, and the galaxies to the north have yet to fall in.