A study of the ground-state hydroxyl maser emission associated with 11 regions of star formation

Abstract

The results of an arcsecond-resolution study of the four ground-state hydroxyl masers and 15 GHz continuum emission associated with 11 regions of star formation are reported. Within the 11 regions, over 30 individual sites of maser emission, which are typically closely associated with 15 GHz continuum emission, are identified. Within a particular cluster, different maser transitions are frequently found within 0.5 arcsec of each other, suggesting that several transitions can be pumped in very similar physical condensations. Twenty percent of the maser clusters do not appear closely associated with 15 GHz continuum sources. The findings do not support the idea that hydroxyl masers are uniformly distributed in a thin or thick shell surrounding a central star, or that amplification of continuum background photons plays a significant part in determining the output intensities of hydroxyl masers.