GBT24A-237

A Search for Dust-free Clouds in the Galactic Disk

Abstract

The Milky Way needs a continuing supply of fresh gas to main its star formation and to account for what is known about interstellar abundances. Some of this gas almost certainly comes from high velocity clouds (HVCs), those ubiquitous aggregations of neutral and ionized gas whose kinematics are not strongly coupled to Galactic rotation. We have identified a component of the Smith HVC that is now passing through the Galactic plane contributing mass to the star-forming regions of the inner Galaxy. This new material should have little dust and a low metallicity. We propose to search for 18cm OH emission from clouds that are part of this structure, along with a control sample of "normal" interstellar clouds. Molecules like OH should be present in diffuse ISM clouds but not in the clouds that originated in an HVC, offering a clean test of the difference between these two populations.

If our hypothesis is correct (OH present in "normal" clouds and absent in accreted HVCs), this would provide a means to potentially identify recently accreted clouds in the Galactic Plane.

This proposal is a re-submission of GBT23B-204 in case all observations are not completed.

Investigators

Name	Institution
Toney Minter *	Green Bank Observatory
Jay Lockman	Green Bank Observatory

* indicates the PI