| Abstract | A region 0°.7 × 0°.8 around the SB0 galaxy NGC 1023 has been surveyed in H I with the MK IA radio telescope (beamwidth 0°.2 × 0°.2). NGC 1023, which has a heliocentric velocity of 607 km s-1, shows clear rotation, has a hydrogen mass of 1.1 × 109 Msun and has a total mass-to- luminosity ratio of 8.5. Of particular interest is the discovery of a possible intergalactic H I cloud 14 arcmin from NGC 1023 which has a heliocentric velocity of 882 km s-1 and a hydrogen mass of 0.7 × 109 Msun. There is no apparent optical counterpart to this object. The members of the NGC 1023 group divide into two distinct velocity groupings. The lower velocity group at 732 km s-1, corrected for the motion of the Galaxy, contains 11 members for which the virial theorem mass is three to four times the sum of the masses of the individual galaxies and thus may be loosely bound. The mean observed total mass-to-luminosity ratio for this group is 10 while the virial mass-to-luminosity ratio is 38 - a value three to four times lower than derived optically for some small groups. It is likely that the higher velocity group at 1066 km s-1, which includes the H I cloud, is more distant than the main NGC 1023 group of galaxies. |
