GBT21A-092

Carbon-grain Sublimation: A New Top-down Component of Protostellar Chemistry

Abstract

A longstanding puzzle in our understanding of planet formation is the low carbon content of our own Earth: a 2-4 orders of magnitude depletion with respect to interstellar grains. The only solution to this conundrum is that carbon grains are destroyed early on in the planet-formation process (during the protostellar phase). As the return of refractory carbon to the gas phase is central to the supply of carbon to terrestrial worlds, constraining the responsible mechanism is of fundamental importance. A promising mechanism is the thermal sublimation of carbon grains at temperatures above ~300 K. A first step in validating this mechanism is establishing the presence of >300 K gas around low-mass protostars. However, this gas is impossible to probe at sub-mm wavelengths due to optically thick dust. By providing high sensitivity at longer wavelengths at which the effects of dust optical depth are minimized, the GBT plays a crucial role in solving the missing-carbon problem. We propose to reveal this hidden hot gas by observing a sample of six low-mass protostars. In addition, two high-mass protostars are observed to characterize this top-down chemistry component that starts from the destruction of larger species instead of bottom up from atoms.

Investigators

Name	Institution
Merel van 't Hoff *	Purdue University
Ted Bergin	Michigan at Ann Arbor, University of

* indicates the PI