DEUTERATED AMMONIA ISOTOPIC FRACTIONATION IN PRESTELLAR CORE L43E

Abstract

Prestellar cores are nitrogen-rich, bound, dense regions within molecular clouds that will eventually lead to star formation. Throughout the interstellar medium, the two stable isotopes of nitrogen, 14N and 15N, are generally found in a ratio of around 330. The nitrogen isotopic fractionation ratio has been observed in fewer than 10 prestellar cores. Chemodynamical core models have difficulty predicting the observed fractionation ratios, which vary widely between different nitrogen-bearing species and different sources, and have difficulty in constraining the fractionation mechanisms of nitrogen-bearing isotopes. We observed the 14N and 15N isotopes of ortho-NH2D in prestellar core L43E using the Arizona Radio Observatory 12m radio telescope on Kitt Peak. Using the radiative transfer software RADEX, we constrained the fractionation ratio to 264+102−72 . Our findings do not support significant fractionation in L43E, and suggest that traditional assumptions, such as assuming identical excitation temperatures for the two molecular nitrogen-bearing species, may not be appropriate.