A survey of hydroxyl in three translucent molecular clouds

This work addresses the issue of using the hydroxyl molecule to trace H2 by studying three high-latitude translucent molecular clouds: MBM03, MBM16, and MBM40. OHs efficiency as a tracer was determined by comparing it to the amount of H2 for various cloud positions. Comparisons were also made to other molecular tracers: CO and CH. As a precursor to the formation of CO, it was hypothesized that OH should trace H2 at lower densities. The results show that OH has a strong correlation to the dust content of all the clouds, E(BV). Coupled with the theoretical predictions of astrochemical theories, these results indicate that OH is an effective tracer of H2 at low extinctions. It can also provide new information about cloud dynamics, particularly for clouds with a variable XCO factor. However, different clouds give different results, indicating that OH is not necessarily the most efficient tracer for all clouds.