GBT20B-014

A GBT Search for an Extended Disk of OH Emission in M33

Abstract

In 2012 we carried out a pilot study (GBT/12A-269) to determine whether our observations of ubiquitous thermal OH emission in the Galaxy could be repeated in M33. That program failed to yield a detection, and since 2012 we have focused our efforts on observing 18cm OH emission with the GBT at various directions towards the Outer Galaxy. Very recently, we have uncovered evidence that an extended disk of OH emission exists in the outer Galaxy beyond the solar circle. This disk has a surface brightness of order 1-2 mK and is smoothly extended, underlying more "lumpy" OH concentrations in the Perseus and Outer arms. If such a disk exists in M33, then the area filling factor would be essentially unity in the GBT beam at the distance of M33. This disk is observable in the Galaxy with integrations of typically 10 hours with the GBT. The 2-hr integration times we spent at each pointing in the 2012 study may have been inadequate to reveal such a disk in M33. This proposal aims to correct that error by requesting 70 hours of GBT time in a concerted effort to reveal a similar molecular disk in M33.

Investigators

Name	Institution
Michael Busch *	California at San Diego, University of
David Hogg	National Radio Astronomy Observatory
Ron Allen	Space Telescope Science Institute

* indicates the PI