Nitrogen isotopes in the interstellar medium: A chemical journey across the Galaxy

Abstract

One of the most important tools to investigate the chemical history of our Galaxy and our own Solar System is to measure the isotopic fractionation of chemical elements. This is the process that distributes the less abundant stable isotopes of an element in different molecules. The isotopic ratios are governed by two main processes: 1. chemical evolution of the whole Galaxy due to stellar nucleosynthesis; 2. local fractionation effects. In this Proceeding we report some results highlighting both processes towards massive star-forming regions.

Nitrogen fractionation in ammonia and its insights into nitrogen chemistry

“…To the best of our knowledge, in the local ISM 15 NH 3 detection has been reported only in Barnard 1 and NGC 1333 (Lis et al 2010) 1 , with 14 N/ 15 N = 334±50 (Barnard 1) and 344± 173 (NGC 1333), which are consistent with the nitrogen isotopic ratio in the local interstellar medium (300−400;Hily-Blant et al 2017;Kahane et al 2018;Colzi et al 2018). Gerin et al (2009) reported a small sample of 14 N/ 15 N measurements in deuterated ammonia (NH 2 D).…”

“…L1544 is a cold and highly concentrated prestellar core, reaching at its centre T ∼ 7 K and n ∼ 10 7 cm −3 (Crapsi et al 2007;Keto et al 2015). It already shows signs of gravitational contraction, also well extended in its envelope (Crapsi et al 2005;Redaelli et al 2022). The uneven illumination from the interstellar radiation field might be responsible for its diversified chemistry (Spezzano et al 2017).…”