The Chemical Clock of High-mass Star-forming Regions: N2H+/CCS
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arXiv
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| Auteurs principaux: | , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866910973668884480 |
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| author | Chen, J. L. Zhang, J. S. Ge, J. X. Wang, Y. X. Yu, H. Z. Zou, Y. P. Yan, Y. T. Wang, X. Y. Wei, D. Y. |
| author_facet | Chen, J. L. Zhang, J. S. Ge, J. X. Wang, Y. X. Yu, H. Z. Zou, Y. P. Yan, Y. T. Wang, X. Y. Wei, D. Y. |
| contents | Using the IRAM 30 m telescope, we presented observations of N2H+ J = 1-0, CCS JN = 87-76 and 77-66 lines toward a large sample of ultracompact HII regions (UC HIIs). Among our 88 UC HIIs, 87 and 33 sources were detected in the N2H+ J = 1-0 and CCS JN = 87-76 lines, respectively. For the CCS 77-66 transition, we detected emission in 10 out of 82 targeted sources, all of which also exhibited emission in the CCS JN = 87-76 line. Physical parameters are derived for our detections, including the optical depth and excitation temperature of N2H+, the rotational temperature of CCS and the column density. Combining our results and previous observation results in different stages of high-mass star-forming regions (HMSFRs), we found that the column density ratio N(N2H+)/N(CCS) increases from high-mass starless cores (HMSCs) through high-mass protostellar cores (HMPOs) to UC HIIs. This implies that N(N2H+)/N(CCS) can trace the evolution process of HMSFRs. It was supported by our gas-grain chemical model, which shows that N(N2H+)/N(CCS) increases with the evolution age of HMSFRs. The temperature, density and chemical age were also constrained from our best-fit model at each stage. Thus, we propose N(N2H+)/N(CCS) as a reliable chemical clock of HMSFRs. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2505_23221 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The Chemical Clock of High-mass Star-forming Regions: N2H+/CCS Chen, J. L. Zhang, J. S. Ge, J. X. Wang, Y. X. Yu, H. Z. Zou, Y. P. Yan, Y. T. Wang, X. Y. Wei, D. Y. Astrophysics of Galaxies Using the IRAM 30 m telescope, we presented observations of N2H+ J = 1-0, CCS JN = 87-76 and 77-66 lines toward a large sample of ultracompact HII regions (UC HIIs). Among our 88 UC HIIs, 87 and 33 sources were detected in the N2H+ J = 1-0 and CCS JN = 87-76 lines, respectively. For the CCS 77-66 transition, we detected emission in 10 out of 82 targeted sources, all of which also exhibited emission in the CCS JN = 87-76 line. Physical parameters are derived for our detections, including the optical depth and excitation temperature of N2H+, the rotational temperature of CCS and the column density. Combining our results and previous observation results in different stages of high-mass star-forming regions (HMSFRs), we found that the column density ratio N(N2H+)/N(CCS) increases from high-mass starless cores (HMSCs) through high-mass protostellar cores (HMPOs) to UC HIIs. This implies that N(N2H+)/N(CCS) can trace the evolution process of HMSFRs. It was supported by our gas-grain chemical model, which shows that N(N2H+)/N(CCS) increases with the evolution age of HMSFRs. The temperature, density and chemical age were also constrained from our best-fit model at each stage. Thus, we propose N(N2H+)/N(CCS) as a reliable chemical clock of HMSFRs. |
| title | The Chemical Clock of High-mass Star-forming Regions: N2H+/CCS |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2505.23221 |