VLA HI imaging of the brightest spiral galaxies in Coma

Abstract

We have obtained 21cm 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 (1.2 degrees). The HI detected, yet deficient galaxies show a strong correlation in their HI properties with projected distance from the cluster center. The most strongly HI deficient (HI Def > 0.4) galaxies are located inside a radius of 30 arcmin (aprox 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 HI distribution and/or shifts between the optical and 21cm positions. Seven so called blue disk galaxies in Coma were observed in HI and six were detected. We did a more sensitive search for HI from 11 of the 15 known post starburst galaxies in Coma. None were detected with typical HI mass limits between 3 and 7x10^7 solar masses. Our results present and enhance a picture already familiar for well studied clusters. HI poor galaxies are concentrated toward the center of the cluster. The HI morphology of the central galaxies, with optical disks extending beyond the HI disks is unique to cluster environments and strongly suggests an interaction with the 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 non-detections are to the west. In the outer parts the gas rich galaxies are north of Coma, non-detected spirals are found in the NGC 4944 group to the east and NGC 4839 group to the SW. This supports recent findings that merging of groups is ongoing in the center of Coma, further out the NGC 4944 and NGC 4839 must have passed through the core, while the galaxies to the north have yet to fall in.