Organic Deuteration in Starless Cores

Abstract

Starless cores and gravitationally-bound, collapsing prestellar cores are the incipient phase of star and planet formation. We must understand the evolution of starless and prestellar cores, as the initial conditions of the future protoplanetary disk are set during this phase. A comparison of the chemical maturity of a starless core with its physical properties, such as central density, kinetic temperature, and virial stability, allows for characterization of its chemical evolution rate. Deuteration, where deuterium replaces one or more hydrogen atoms in a molecule, is favored in the cold, dense environments of starless cores, making it a very effective probe of chemical maturity. The B10 region of the Taurus Molecular Cloud is a pristine environment for the study of starless core evolution due to its lack of embedded protostars. We surveyed 11 cores in B10 in oH2CO, HDCO, and pD2CO with the ARO 12m telescope. We find that HDCO, previously thought to deuterate primarily on icy grain surfaces, does not correlate well with CH2DOH, a known tracer of icy grain surface deuteration. We investigate the possibility of a gas-phase component to HDCO deuteration by comparing it to N2D+, a known gas-phase deuteration tracer. We find a general lack of correlation between deuterated organic molecules and the physical parameters of the cores. This may indicate that the cores are evolving at different rates, and that deuteration provides a unique measure of core chemical evolution.