2 Observational results

Our data consist of 21 cm line data obtained with the VLA. Twelve fields within one Abell radius of the Coma cluster (equivalent to 1.2$^{\circ}$) were observed with the VLA in its C configuration, and two of them reobserved in D configuration. The observed fields and the distribution of the 19 galaxies detected in H I around the cluster are shown in Paper I (Figs. 1 and 2). Most of the fields are devoted to the center of Coma and the regions where SB and PSB galaxies had been reported from optical observations. Our velocity resolution is 21 kms^-1, and 43 kms^-1 for some of the galaxies observed in both C and D configurations. The angular resolution ranges between 20 and 35 arcsec. The rms in the final cubes is between 0.35 and 0.40 mJy beam^-1, except in those fields observed in both C and D configurations, reaching rms values as low as 0.20 mJy beam^-1. Most of the channel maps shown in the Appendix (electronic version) are smoothed in velocity. More details on the H I observations are given in Paper I.

Eight out of the 19 detected galaxies are projected within 0.5 Mpc from the cluster center (we consider the position of the cD NGC4874 as the Coma center). These central galaxies lie inside or near the hot ICM as traced by the ROSAT X-ray emission (Briel et al. 1992; Vikhlinin et al. 1997), and most of them are very H I deficient. The H I deficiency is measured following Giovanelli & Haynes (1985), comparing the observed H I mass with the expected H I mass of an equivalent isolated spiral. Several galaxies detected in H I near the center of Coma show H I truncated disks as well as offsets between the optical and H I distributions (see Sect. 3). In a few cases unexpected differences between optical and H I velocities are found. Six of the galaxies detected in H I are reported by Bothun & Dressler (1986) as having blue disks; five of these are projected inside or near the cluster X-ray emission. None of the PSB galaxies reported by Caldwell et al. (1993, 1997) were detected in H I; we obtain for some of them H I mass upper limits down to $3 \times 10^7~$$M_{\odot}$.

Our radio continuum images are obtained as a byproduct of the H I observations. The images are built by averaging a set of those line free channels in a given cube. All of the H I detected spirals (except NGC4907) are also detected in the continuum with flux densities ranging between 2 and 16 mJy (see Paper I).