The Young Ages of 70 μm-dark Clumps Inferred from Carbon Chain Chemistry
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arXiv
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| Autori principali: | , , , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| _version_ | 1866917915183284224 |
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| author | Worthen, Kadin Svoboda, Brian E. Meier, David S. Ott, Juergen Friesen, Rachel Patience, Jennifer Shirley, Yancy |
| author_facet | Worthen, Kadin Svoboda, Brian E. Meier, David S. Ott, Juergen Friesen, Rachel Patience, Jennifer Shirley, Yancy |
| contents | The physical conditions of the earliest environment of high-mass star formation are currently poorly understood. To that end, we present observations of the carbon chain molecules HC$_5$N , CCS, and HC$_7$N in the 22-25 GHz band towards 12 high-mass 70 micron-dark clumps (SMDC) with the Jansky Very Large Array (VLA). We detect HC$_5$N and CCS towards 11 of these SMDC sources. We calculate column densities and abundances relative to H$_2$ for HC$_5$N and CCS. We do not find any clear HC$_7$N detections in the 11 sources individually, but by stacking the HC$_7$N spectra, we do detect HC$_7$N on average in these sources. We also calculate the ratio of the column densities of HC$_5$N to HC$_7$N using the stacked spectra of both species. We compare our measured abundances of HC$_5$N and our measured ratio of HC$_5$N to HC$_7$N to the UMIST dark cloud chemistry models to constrain an age for the gas assuming a fixed volume density and temperature. The chemical models favor a chemical evolutionary age less than 1 Myr at densities of n(H2) = 2 x 10$^4$ cm$^{-3}$. The consistent carbon-chain detections and young model-derived ages support the conclusion that these 11 70 micron-dark clumps lack high mass protostars because they are young and not because they are inefficient and incapable of high mass star formation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_04283 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The Young Ages of 70 μm-dark Clumps Inferred from Carbon Chain Chemistry Worthen, Kadin Svoboda, Brian E. Meier, David S. Ott, Juergen Friesen, Rachel Patience, Jennifer Shirley, Yancy Astrophysics of Galaxies Solar and Stellar Astrophysics The physical conditions of the earliest environment of high-mass star formation are currently poorly understood. To that end, we present observations of the carbon chain molecules HC$_5$N , CCS, and HC$_7$N in the 22-25 GHz band towards 12 high-mass 70 micron-dark clumps (SMDC) with the Jansky Very Large Array (VLA). We detect HC$_5$N and CCS towards 11 of these SMDC sources. We calculate column densities and abundances relative to H$_2$ for HC$_5$N and CCS. We do not find any clear HC$_7$N detections in the 11 sources individually, but by stacking the HC$_7$N spectra, we do detect HC$_7$N on average in these sources. We also calculate the ratio of the column densities of HC$_5$N to HC$_7$N using the stacked spectra of both species. We compare our measured abundances of HC$_5$N and our measured ratio of HC$_5$N to HC$_7$N to the UMIST dark cloud chemistry models to constrain an age for the gas assuming a fixed volume density and temperature. The chemical models favor a chemical evolutionary age less than 1 Myr at densities of n(H2) = 2 x 10$^4$ cm$^{-3}$. The consistent carbon-chain detections and young model-derived ages support the conclusion that these 11 70 micron-dark clumps lack high mass protostars because they are young and not because they are inefficient and incapable of high mass star formation. |
| title | The Young Ages of 70 μm-dark Clumps Inferred from Carbon Chain Chemistry |
| topic | Astrophysics of Galaxies Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2502.04283 |