David L. Cotten, Loris Magnani, Elizabeth A. Wennerstrom, Kevin A. Douglas, Joseph S. Onello
We observed 51 positions in the OH 1667 MHz main line transitions in the translucent, high latitude cloud MBM40. We detected OH in 8 out of 8 positions in the molecular core of the cloud and 24 out of 43 in the surrounding, lower extinction envelope and periphery of the cloud. Using a linear relationship between the integrated OH line intensity and E(B-V), we estimate the mass in the core, the envelope, and the periphery of the cloud to be 9.1, 13.7, and 1.5 solar masses. As much as 60% of the total cloud mass may be found in the envelope (0.12 \leq E(B-V) \leq 0.17 mag) and some molecular mass (6%) in the periphery (E(B-V) < 0.12 mag). The OH 1667 MHz line is an excellent tracers of gas in very low extinction regions and high-sensitivity mapping of the envelopes of molecular clouds may reveal the presence of significant quantities of molecular mass.
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http://arxiv.org/abs/1203.0684
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