MUNA Lunch Talk:

Al Wootten


Nitrogen Isotopic Fractionation in Interstellar Ammonia

November 23

12:10PM, Room 230, NRAO, Edgemont Road


Using the Green Bank Telescope, we have obtained accurate measurements of the 14N/15N isotopic ratio in ammonia in two cold interstellar clouds, Barnard 1 and NGC 1333, where high abundances of multiply-deuterated molecules have been observed. The 14N/15N isotopic ratio in Barnard 1, 360 ? 54 (3 sig uncertainty), is particularly well constrained and falls between the local interstellar medium/proto-solar ratio of 450 and the terrestrial atmospheric ratio of 272. The NGC 1333 measurement is consistent with the Barnard 1 result, but has a larger uncertainty. We do not see evidence for the very high 15N enhancements seen in cometary CN. Our observations show that accurate measurements of nitrogen fractionation in ammonia in cold interstellar clouds are feasible using the GBT. Observations of a larger, carefully selected sample of prestellar cores with varying temperatures and gas densities can significantly improve our understanding of the nitrogen fractionation in the local interstellar medium and its relation to the isotopic ratios measured in various solar system reservoirs.