JWST detections of amorphous and crystalline HDO ice toward massive protostars
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2024
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| author | Slavicinska, Katerina van Dishoeck, Ewine F. Tychoniec, Łukasz Nazari, Pooneh Rubinstein, Adam E. Gutermuth, Robert Tyagi, Himanshu Chen, Yuan Brunken, Nashanty G. C. Rocha, Will R. M. Manoj, P. Narang, Mayank Megeath, S. Thomas Yang, Yao-Lun Looney, Leslie W. Tobin, John J. Beuther, Henrik Bourke, Tyler L. Linnartz, Harold Federman, Samuel Watson, Dan M. Linz, Hendrik |
| author_facet | Slavicinska, Katerina van Dishoeck, Ewine F. Tychoniec, Łukasz Nazari, Pooneh Rubinstein, Adam E. Gutermuth, Robert Tyagi, Himanshu Chen, Yuan Brunken, Nashanty G. C. Rocha, Will R. M. Manoj, P. Narang, Mayank Megeath, S. Thomas Yang, Yao-Lun Looney, Leslie W. Tobin, John J. Beuther, Henrik Bourke, Tyler L. Linnartz, Harold Federman, Samuel Watson, Dan M. Linz, Hendrik |
| contents | This work aims to utilize the increased sensitivity and resolution of the JWST to quantify the HDO/H$_{2}$O ratio in ices toward young stellar objects (YSOs) and to determine if the HDO/H$_{2}$O ratios measured in the gas phase toward massive YSOs (MYSOs) are representative of the ratios in their ice envelopes. Two protostars observed in the Investigating Protostellar Accretion (IPA) program using JWST NIRSpec were analyzed: HOPS 370, an intermediate-mass YSO (IMYSO), and IRAS 20126+4104, a MYSO. The HDO ice toward these sources was detected above the 3$σ$ level and quantified via its 4.1 $μ$m band. The contributions from the CH$_{3}$OH combination modes to the observed optical depth in this spectral region were constrained via the CH$_{3}$OH 3.53 $μ$m band to ensure that the integrated optical depth of the HDO feature was not overestimated. H$_{2}$O ice was quantified via its 3 $μ$m band. From these fits, ice HDO/H$_{2}$O abundance ratios of 4.6$\pm$1.8$\times$10$^{-3}$ and 2.6$\pm$1.2$\times$10$^{-3}$ are obtained for HOPS 370 and IRAS 20126+4104, respectively. The simultaneous detections of both crystalline HDO and crystalline H$_{2}$O corroborate the assignment of the observed feature at 4.1 $μ$m to HDO ice. The ice HDO/H$_{2}$O ratios are similar to the highest reported gas HDO/H$_{2}$O ratios measured toward MYSOs as well as the hot inner regions of isolated low-mass protostars, suggesting that at least some of the gas HDO/H$_{2}$O ratios measured toward massive hot cores are representative of the HDO/H$_{2}$O ratios in ices. The need for an H$_{2}$O-rich CH$_{3}$OH component in the CH$_{3}$OH ice analysis supports recent experimental and observational results that indicate that some CH$_{3}$OH ice may form prior to the CO freeze-out stage in H$_{2}$O-rich ice layers. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2404_15399 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | JWST detections of amorphous and crystalline HDO ice toward massive protostars Slavicinska, Katerina van Dishoeck, Ewine F. Tychoniec, Łukasz Nazari, Pooneh Rubinstein, Adam E. Gutermuth, Robert Tyagi, Himanshu Chen, Yuan Brunken, Nashanty G. C. Rocha, Will R. M. Manoj, P. Narang, Mayank Megeath, S. Thomas Yang, Yao-Lun Looney, Leslie W. Tobin, John J. Beuther, Henrik Bourke, Tyler L. Linnartz, Harold Federman, Samuel Watson, Dan M. Linz, Hendrik Solar and Stellar Astrophysics Astrophysics of Galaxies This work aims to utilize the increased sensitivity and resolution of the JWST to quantify the HDO/H$_{2}$O ratio in ices toward young stellar objects (YSOs) and to determine if the HDO/H$_{2}$O ratios measured in the gas phase toward massive YSOs (MYSOs) are representative of the ratios in their ice envelopes. Two protostars observed in the Investigating Protostellar Accretion (IPA) program using JWST NIRSpec were analyzed: HOPS 370, an intermediate-mass YSO (IMYSO), and IRAS 20126+4104, a MYSO. The HDO ice toward these sources was detected above the 3$σ$ level and quantified via its 4.1 $μ$m band. The contributions from the CH$_{3}$OH combination modes to the observed optical depth in this spectral region were constrained via the CH$_{3}$OH 3.53 $μ$m band to ensure that the integrated optical depth of the HDO feature was not overestimated. H$_{2}$O ice was quantified via its 3 $μ$m band. From these fits, ice HDO/H$_{2}$O abundance ratios of 4.6$\pm$1.8$\times$10$^{-3}$ and 2.6$\pm$1.2$\times$10$^{-3}$ are obtained for HOPS 370 and IRAS 20126+4104, respectively. The simultaneous detections of both crystalline HDO and crystalline H$_{2}$O corroborate the assignment of the observed feature at 4.1 $μ$m to HDO ice. The ice HDO/H$_{2}$O ratios are similar to the highest reported gas HDO/H$_{2}$O ratios measured toward MYSOs as well as the hot inner regions of isolated low-mass protostars, suggesting that at least some of the gas HDO/H$_{2}$O ratios measured toward massive hot cores are representative of the HDO/H$_{2}$O ratios in ices. The need for an H$_{2}$O-rich CH$_{3}$OH component in the CH$_{3}$OH ice analysis supports recent experimental and observational results that indicate that some CH$_{3}$OH ice may form prior to the CO freeze-out stage in H$_{2}$O-rich ice layers. |
| title | JWST detections of amorphous and crystalline HDO ice toward massive protostars |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2404.15399 |