A Window into Chemistry on Icy Dust Grains - the Deuterated NH3 and CH3OH in Ophiuchus

Abstract

Observing CH3OH and CH2DOH, which enter the gas phase through non-thermal desorption in starless cores, allows us to peer through a window onto the icy surfaces of dust grains at the earliest part of the star formation process. Observations of starless and prestellar cores have detected singly deuterated methanol (CH2DOH) at a 75% detection rate and at abundances more than four orders of magnitude larger than the atomic D/H ratio. However, all but two of the published observations are in Taurus with only one core observed in Ophiuchus. Using the Arizona Radio Observatory 12 m telescope, we observe methanol (CH3OH), CH2DOH, and singly deuterated ammonia (NH2D) in starless and prestellar cores in Ophiuchus with the coldest dust temperatures, comparing the deuterium fractions on icy dust grains with those in the gas phase. Additionally, gas in Ophiuchus - a more active star forming region than Taurus - is disturbed as stars form, which may cause prestellar cores to evolve chemically and physically at different rates than those in Taurus, leading to a different distribution of deuterium fractions in prestellar cores with otherwise similar conditions. This survey will allow us to compare the deuterium fractions between Ophiuchus and Taurus in cores with similar average densities. We will also examine the relationship between the deuterium fractions in cores of Ophiuchus with the physical parameters in starless and prestellar cores such as density, temperature, and virial ratio.