Multiaperture Spectroscopy of Galaxies in Abell 370

Results of spectroscopic observations of 30 galaxies in the distant rich cluster Abell 370 at z = 0.376 are presented which confirm the large fraction of blue galaxies in this cluster measured photometrically by Butcher and Oemler (1978, 1984). None of the spectra can be attributed to active galactic nuclei. All blue galaxy spectra may be described as examples of poststarburst objects with strong higher order Balmer lines and very weak or absent emission lines. A comparison of these data with synthetic spectral calculations indicates that a wide range of burst parameters is needed to describe the blue galaxies. From 1 percent to 10 percent of the galaxy mass forming stars between 30 and 200 million years prior to the epoch of observation spans the allowed range.