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A Possible Chemical Clock in High-mass Star-forming Regions: N(HC3N)/N(N2H+)?
- Source :
- The Astrophysical Journal Supplement Series, Vol 264, Iss 2, p 48 (2023)
- Publication Year :
- 2023
- Publisher :
- IOP Publishing, 2023.
-
Abstract
- We conducted observations of multiple HC _3 N ( J = 10−9, 12−11, and 16−15) lines and the N _2 H ^+ ( J = 1−0) line toward a large sample of 61 ultracompact (UC) H ii regions, through the Institut de Radioastronomie Millmétrique 30 m and the Arizona Radio Observatory 12 m telescopes. The N _2 H ^+ J = 1−0 line is detected in 60 sources and HC _3 N is detected in 59 sources, including 40 sources with three lines, 9 sources with two lines, and 10 sources with one line. Using the rotational diagram, the rotational temperature and column density of HC _3 N were estimated toward sources with at least two HC _3 N lines. For 10 sources with only one HC _3 N line, their parameters were estimated, taking one average value of T _rot . For N _2 H ^+ , we estimated the optical depth of the N _2 H ^+ J = 1−0 line, based on the line intensity ratio of its hyperfine structure lines. Then the excitation temperature and column density were calculated. When combining our results in UC H ii regions and previous observation results on high-mass starless cores, the N (HC _3 N)/ N (N _2 H ^+ ) ratio clearly increases from the region stage. This means that the abundance ratio changes with the evolution of high-mass star-forming regions (HMSFRs). Moreover, positive correlations between the ratio and other evolutionary indicators (dust temperature, bolometric luminosity, and luminosity-to-mass ratio) are found. Thus we propose the ratio of N (HC _3 N)/ N (N _2 H ^+ ) as a reliable chemical clock of HMSFRs.
Details
- Language :
- English
- ISSN :
- 15384365 and 00670049
- Volume :
- 264
- Issue :
- 2
- Database :
- Directory of Open Access Journals
- Journal :
- The Astrophysical Journal Supplement Series
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.51f44e7bf4c442a84fbda1ce5d1151f
- Document Type :
- article
- Full Text :
- https://doi.org/10.3847/1538-4365/acafe6