Astrochemistry

An Analysis Of The Isomers HCN And HNC In The Evolution Of High-mass Star-forming Regions

By Keith Cowing
Status Report
astro-ph.GA
July 8, 2023
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An Analysis Of The Isomers HCN And HNC In The Evolution Of High-mass Star-forming Regions
Left: Kinetic temperature of ammonia vs. dust temperature obtained from the PPMAP procedure done to the Hi-GAL maps (Marsh et al., 2017). Center: Kinetic temperature of ammonia vs. kinetic temperature derived from the HCN-HNC integrated intensity ratio. Right: Dust temperature vs. kinetic temperature derived from the HCN-HNC integrated intensity ratio. The blue line in all cases indicates the unity. — astro-ph.GA

The study of molecules and their chemistry in star-forming regions is fundamental to understand the physical process occurring in such regions.

The HCN and HNC J=1-0 emissions were used to derive their integrated line intensities (I), to probe a relation recently appeared in the literature between the kinetic temperatures (TK) and the isomeric (I) ratio, and to obtain the isomers abundances (X) in 55 high-mass star-forming regions. These last ones are classified, according to the evolutive stage, as infrared dark clouds, high-mass protostellar objects, hot molecular cores, and ultracompact HII regions.

It is inferred that the TK obtained from the isomeric integrated intensity ratio (IHCN/HNC) are underestimated, and hence we suggest that this relation cannot be employed as an universal thermometer in the interstellar medium. The isomers abundances show a behavior that can be explained from the chemistry occurring as the temperature and the UV radiation increase according to the evolutive stage.

We found that the abundance ratio (XHCN/HNC) hardly could be used as a chemical clock, and we suggest that it can be approximated by IHCN/HNC. This work is part of an on-going study of multiple molecules that stand in the sample of analyzed regions which intends to contribute in the chemical knowledge of high-mass star formation.

N.C. Martinez, S. Paron

Comments: to appear in BoletĂ­n de la AsociaciĂłn Argentina de AstronomĂ­a
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2305.05073 [astro-ph.GA] (or arXiv:2305.05073v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2305.05073
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Submission history
From: Sergio Paron
[v1] Mon, 8 May 2023 22:21:22 UTC (91 KB)
https://arxiv.org/abs/2305.05073
Astrobiology, Astrochemistry

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