GBT26A-578

Extending the GBT M31 Molecular Ring Survey in OH

Abstract

We propose to extend the GBT OH Survey of M31 from the previous semester (GBT25A_129) to include the southern molecular ring of M31. Preliminary results are promising and show that 'normal' or 'thermal' OH emission is four times brighter in the molecular ring than in the outskirts of the galaxy as shown in Busch 2024, which was the GBT pilot survey that prompted this effort.

We ask for half the integration time per sightline and slightly expand our number of sightlines asked here to 22 at five hours per sightline. As OH emission here is around 4-10 mK, the 2mK per channel is more than enough to ensure sensitive data that can produce science ready results, such as comparing OH column densities and the FWHM between the CO and OH lines in M31. The data proposed here will serve as a sensitive legacy dataset in the GBT archive and an alternative check on the "CO-dark gas" content in the nearest Milky Way analog.

Investigators

Name	Institution
GBT Operator	Green Bank Observatory
Michael Busch *	National Radio Astronomy Observatory

* indicates the PI