Nancay "blind" 21 cm line survey of the Canes Venatici group region

A radio spectroscopic driftscan survey in the 21 cm line with the Nancay de cimetric radio telescope of 0.08 steradians of sky in the direction of the constellation Canes Venatici covering a heliocentric velocity range of -350 < V-hel < 2350 kms(-1) produced 53 spectral features, which was further re duced to a sample of 33 reliably detected galaxies by extensive follow-up o bservations. With a typical noise level of rms = 10 mJy after Hanning smoot hing, the survey is - depending on where the detections are located with re gard to the centre of the beam sensitive to M-HI = 1 - 2 10(8) h(-2)M(.) at 23 h(-1) Mpc and to M-HI = 4 - 8 10(7) h(-2)M(.) throughout the CVn groups . The survey region had been previously examined on deep optical plates by Bi nggeli et al. (1990) and contains loose groups with many gas-rich galaxies as well as voids. No galaxies that had not been previously identified in th ese deep optical surveys were uncovered in our HI survey, neither in the gr oups nor the voids. The implication is that no substantial quantity of neut ral hydrogen contained in gas-rich galaxies has been missed in these well-s tudied groups. All late-type members of our sample are listed in the Fisher & Tully (1981b) optically selected sample of nearby late-type galaxies; th e only system not contained in Fisher and Tully's Catalog is the SO galaxy NGC 4203. Within the well-sampled CVn group volume with distances corrected for flow motions, the HI mass function is best fitted with the Zwaan et al . (1997) HI mass function (alpha = -1.2) scaled by a factor of f = 4.5 in a ccount of the locally overdense region.