GBT24A-232

The Dark Carbon Falls - An ARKHAM Pilot Project

Abstract

Individual PAH molecules have been detected using the GBT in TMC-1 and benzene has been found by JWST in the J160532 protoplanetary disk. The chemical and physical processes in the intervening stages is not well-understood. This proposal is for pilot observations to explore the mechanism by which the unsaturated, carbon-rich gas-phase chemistry of dark clouds is transformed into the oxygen-rich, saturated chemical inventory of star-forming regions. From an organic chemistry perspective, the destruction of large, unsaturated hydrocarbons and PAHs by reactive oxygen and hydrogen (H, OH, aldehyde [=O] groups, etc.) liberated from icy grain surfaces is an appealing explanation. These observations are designed to test whether this can be achieved largely through the UV-induced photodesorption of water-rich ices, or whether the thermally and kinematically hot environments of a protostar are required. We will conduct pilot deep-drill observations of unsaturated carbon-rich species in each of two active PDR regions: the Orion Bar PDR and the Horsehead PDR. If these preliminary observations show evidence of hydrocarbon erosion in the absence of a protostar, they will form the basis of a GBT Large Proposal to conduct ultra-deep line surveys to explore this chemical transition space. These will be operator-driven, flexible observations.

Investigators

Name	Institution
Brett McGuire *	National Radio Astronomy Observatory; Massachusetts Institute of Technology
Tony Remijan	National Radio Astronomy Observatory
Andrew Lipnicky	National Radio Astronomy Observatory; Rochester Institute of Technology
Andrew Burkhardt	Center for Astrophysics | Harvard & Smithsonian; Wellesley College; Worcester State University
Ilsa Cooke	British Columbia, University of; Rennes 1, Université de
Jasmine So Yee Cheung	Massachusetts Institute of Technology
Alex Byrne	Massachusetts Institute of Technology
Ted Bergin	Michigan at Ann Arbor, University of

* indicates the PI