The Apparent Radial Velocities of 100 Extra-Galactic Nebulae

Abstract

New velocities of 100 nebulae are given in Table I. With the exception of 6, they are all velocities of recession ranging from +50 km/sec, for a member of the Virgo Cluster, to +42,000 km/sec for a member of the Ursa Major Cluster No. 2. In the Virgo Cluster 25 new velocities have been obtained, 9 of them by Sinclair Smith. These, with velocities previously known, show an average range of 500 km/sec around a mean of +1200 km/sec. Magnitudes range from io.o to 15.0. The mean velocity of the fainter members is approximately the same as that of the brighter. Late-type spirals (Sc) are decidedly bluer than E, Sa, or Sb nebulae. The mean spectral type for these groups is: Eo-7, G3.6; Sa, G3.4; Sb, Gi.6; Sc, F8.8. Velocities of the order of +40,000 km/sec have been observed in the Boötes Cluster and in the Ursa Major Cluster No. 2. These values are consistent with estimates of the distance by Hubble and Baade (about ~o million parsecs for both clusters) and indicate that the velocity-distance relation is still sensibly linear to this distance