On the birthplaces of stars

Abstract

The numbers, ages, and stellar content of open clusters, OB, T, and R associations have been surveyed in order to estimate the amount of mass presently being processed into stars by these groups and to determine the fraction of field stars which were born in each type of group. Clusters can account for about 10% of all stars presently being formed, in agreement with previous estimates. Associations can reasonably account for all stars more massive than 2 to 5 solar masses which are not formed in clusters, and can account for stars of all masses if the association and field-star luminosity functions are similar. If associations are deficient in low-mass stars relative to the field, then an additional birthplace is required.