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Title: FIRST MEASUREMENTS OF {sup 15}N FRACTIONATION IN N{sub 2}H{sup +} TOWARD HIGH-MASS STAR-FORMING CORES

We report on the first measurements of the isotopic ratio {sup 14}N/{sup 15}N in N{sub 2}H{sup +} toward a statistically significant sample of high-mass star-forming cores. The sources belong to the three main evolutionary categories of the high-mass star formation process: high-mass starless cores, high-mass protostellar objects, and ultracompact H ii regions. Simultaneous measurements of the {sup 14}N/{sup 15}N ratio in CN have been made. The {sup 14}N/{sup 15}N ratios derived from N{sub 2}H{sup +} show a large spread (from ∼180 up to ∼1300), while those derived from CN are in between the value measured in the terrestrial atmosphere (∼270) and that of the proto-solar nebula (∼440) for the large majority of the sources within the errors. However, this different spread might be due to the fact that the sources detected in the N{sub 2}H{sup +} isotopologues are more than those detected in the CN ones. The {sup 14}N/{sup 15}N ratio does not change significantly with the source evolutionary stage, which indicates that time seems to be irrelevant for the fractionation of nitrogen. We also find a possible anticorrelation between the {sup 14}N/{sup 15}N (as derived from N{sub 2}H{sup +}) and the H/D isotopic ratios. This suggests that {sup 15}Nmore » enrichment could not be linked to the parameters that cause D enrichment, in agreement with the prediction by recent chemical models. These models, however, are not able to reproduce the observed large spread in {sup 14}N/{sup 15}N, pointing out that some important routes of nitrogen fractionation could be still missing in the models.« less
Authors:
 [1] ; ;  [2] ;  [3] ;  [4]
  1. INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy)
  2. Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, D-85748 Garching (Germany)
  3. Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, P.O. Box 3-72, 58090 Morelia, Michoacán, México (Mexico)
  4. Univ. Grenoble Alpes, IPAG, F-38000 Grenoble (France)
Publication Date:
OSTI Identifier:
22518922
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 808; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON NITRIDES; CYANIDES; FRACTIONATION; ISOTOPE RATIO; MASS; MOLECULES; NITROGEN; NITROGEN 14; NITROGEN 15; SOLAR NEBULA; STAR EVOLUTION; STARS