Astron. Astrophys. Suppl. Ser. 135, 255-271

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

R.C. Kraan-Korteweg^1,2 - W. van Driel³ - F. Briggs⁴ - B. Binggeli⁵ - T.I. Mostefaoui²

Send offprint request: R.C. Kraan-Korteweg, Universidad de Guanajuato, Mexico; e-mail: kraan@astro.ugto.mx

1 - Departemento de Astronomia, Universidad de Guanajuato, Apartado Postal 144 Guanajuato, GTO 36000, Mexico
2 - DAEC, Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon Cedex, France
3 - Unité Scientifique Nançay, CNRS USR B704, Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon Cedex, France
4 - Kapteyn Astronomical Institute, Groningen University, P.O. Box 800, NL-9700 AV Groningen, The Netherlands
5 - Astronomical Institute, University of Basel, Venusstrasse 7, CH-4102 Binningen, Switzerland

Received September 23; accepted November 3, 1998

Abstract:

A radio spectroscopic driftscan survey in the 21 cm line with the Nançay decimetric radio telescope of 0.08 steradians of sky in the direction of the constellation Canes Venatici covering a heliocentric velocity range of $-350 < V_{\rm hel} < 2350$ kms^-1 produced 53 spectral features, which was further reduced to a sample of 33 reliably detected galaxies by extensive follow-up observations. With a typical noise level of $\rm rms = 10\,mJy$ after Hanning smoothing, the survey is - depending on where the detections are located with regard to the centre of the beam - sensitive to $M_{\rm HI} = 1-2 {\ }10^8\, {h}^{-2}$${ M}_\odot$ at $23 \,{h}^{-1}$ Mpc and to $M_{\rm HI} = 4-8 {\ }10^7\, {h}^{-2}$${ M}_\odot$ throughout the CVn groups.

The survey region had been previously examined on deep optical plates by Binggeli 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 these deep optical surveys were uncovered in our HI survey, neither in the groups nor the voids. The implication is that no substantial quantity of neutral hydrogen contained in gas-rich galaxies has been missed in these well-studied groups. All late-type members of our sample are listed in the Fisher & Tully (1981b) optically selected sample of nearby late-type galaxies; the only system not contained in Fisher and Tully's Catalog is the S0 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 account of the locally overdense region.

Key words: galaxies: distances and redshifts -- galaxies: general -- galaxies: ISM -- radio lines: galaxies -- surveys