Systematic reinvestigation of the radial velocities of the galactic globular clusters - Image-tube results

Abstract

Radial velocities measured from around 260 image-tube spectrograms at 120 A/mm, obtained between 1975 and 1978 with the 1-m Yale-Tololo telescope, of 90 globular clusters, NGC 121 in the Small Magellanic Cloud, and 23 evolved stars in four globular clusters, are presented and compared with previous data. Internal plus external measuring errors are estimated to be around 20 km/s per plate. Solid-body solar-motion solutions are used to investigate the impact of the homogeneous velocities on earlier studies, and good overall agreement is found with the velocities of Mayall (1946), Kinman (1959), Webbink (1981), and Zinn and West (1984). From the present data, the solar motion apex is calculated to lie at alpha of 21 h 10 m + or - 52 m and delta of 44.9 + or - 9.8 deg, and the velocity dispersion for the cluster as a whole is calculated to be around 120 km/s. Evidence confirms the G-type clusters rotating more rapidly than the F-type ones.