Abstract. High sensitivity (rms noise ∼ 0.5 mJy) 21-cm H i line observations were made of 33 galaxies in the Virgo cluster, using the refurbished Arecibo telescope, which resulted in the detection of 12 objects. These data, combined with the measurements available from the literature, provide the first set of H i data that is complete for all 355 late-type (Sa-Im-BCD) galaxies in the Virgo cluster with mp ≤ 18.0 mag. The Virgo cluster H i mass function (HIMF) that was derived for this optically selected galaxy sample is in agreement with the HIMF derived for the Virgo cluster from the blind HIJASS H i survey and is inconsistent with the Field HIMF. This indicates that both in this rich cluster and in the general field, neutral hydrogen is primarily associated with late-type galaxies, with marginal contributions from early-type galaxies and isolated H i clouds. The inconsistency between the cluster and the field HIMF derives primarily from the difference in the optical luminosity function of late-type galaxies in the two environments, combined with the HI deficiency that is known to occur in galaxies in rich clusters.

We present B-and R-band optical imaging and photometry, Hα narrow-band imaging, near-infrared H-band imaging, and H i 21-cm spectroscopy of the nearby (V h =407 km/s), Sd spiral galaxy UGC 7321. UGC 7321 exhibits a remarkably thin stellar disk with no discernible bulge component. The galaxy has a very diffuse, low surface brightness disk, which appears to suffer relatively little internal extinction in spite of its nearly edge-on geometry (i ≈88 • ). If seen face-on, UGC 7321 would have an observed central B-band surface brightness of only ∼23.4 mag arcsec −2 .The UGC 7321 disk shows significant B − R color gradients in both the radial and vertical directions: ∆(B − R) ≥0.80 magnitudes along the galaxy major axis, and ∆(B − R) as large as 0.45 magnitudes is observed parallel to the galaxy minor axis. These color gradients cannot be explained solely by dust and are indicative of changes in the mix of stellar ages and/or metallicity as a function of both radius and height above the galaxy plane. The outer regions of the UGC 7321 disk are too blue to be explained by low metallicity alone (B − R ≤ 0.6), and must be relatively young. However, the galaxy also contains stellar populations with B − R >1.1, indicating it is not a young or recently-formed galaxy.The disk of UGC 7321 is not a simple exponential, but exhibits a light excess at small radii, as well as distinct surface brightness zones. Despite its organized disk structure, many of the global properties of UGC 7321 (M B = −17.0; M HI =1.1×10 9 M ⊙ ;

High sensitivity 21-cm H i line observations with an rms noise level of ∼0.5 mJy were made of 35 spiral galaxies in the Coma Supercluster, using the refurbished Arecibo telescope, leading to detection of 25 objects. These data, combined with the measurements available in the literature, provide the set of H i data for 94% of all late-type galaxies in the Coma Supercluster with an apparent photographic magnitude m p ≤ 15.7 mag. We confirm that the typical scale of H i deficiency around the Coma cluster is 2 Mpc, i.e. one virial radius. Comparing the H i mass function (HIMF) of cluster with non-cluster members of the Coma Supercluster we detected a shortage of high H i mass galaxies among cluster members that can be attributed to the pattern of H i deficiency found in rich clusters.