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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
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2024
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| Online Access: | https://arxiv.org/abs/2405.16744 |
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| _version_ | 1866913364199866368 |
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| author | Okoda, Yuki Oya, Yoko Sakai, Nami Watanabe, Yoshimasa López-Sepulcre, Ana Oyama, Takahiro Zeng, Shaoshan Yamamoto, Satoshi |
| author_facet | Okoda, Yuki Oya, Yoko Sakai, Nami Watanabe, Yoshimasa López-Sepulcre, Ana Oyama, Takahiro Zeng, Shaoshan Yamamoto, Satoshi |
| contents | Deuterium fractionation in the closest vicinity of a protostar is important in understanding its potential heritage to a planetary system. Here, we have detected the spectral line emission of CH3OH and its three deuterated species, CH2DOH, CHD2OH, and CH3OD, toward the low-mass protostellar source B335 at a resolution of 0.''03 (5 au) with Atacama Large Millimeter/submillimeter Array. They have a ring distribution within the radius of 24 au with the intensity depression at the continuum peak. We derive the column densities and abundance ratios of the above species at 6 positions in the disk/envelope system as well as the continuum peak. The D/H ratio of CH3OH is ~[0.03-0.13], which is derived by correcting the statistical weight of 3 for CH2DOH. The [CHD2OH]/[CH2DOH] ratio is derived to be higher ([0.14-0.29]). On the other hand, the [CH2DOH]/[CH3OD] ratio ([4.9-15]) is higher than the statistical ratio of 3, and is comparable to those reported for other low-mass sources. We study the physical structure on a few au scale in B335 by analyzing the CH3OH (183,15-182,16, A) and HCOOH (120,12-110,11) line emission. Velocity structures of these lines are reasonably explained as the infalling-rotating motion. The protostellar mass and the upper limit to centrifugal barrier are thus derived to be 0.03-0.07 M_{\odot} and <7 au, respectively, showing that B335 harbors a young protostar with a tiny disk structure. Such youth of the protostar may be related to the relatively high [CH2DOH]/[CH3OH] ratio. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2405_16744 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | CH_3OH and Its Deuterated Species in the Disk/Envelope System of the Low-Mass Protostellar Source B335 Okoda, Yuki Oya, Yoko Sakai, Nami Watanabe, Yoshimasa López-Sepulcre, Ana Oyama, Takahiro Zeng, Shaoshan Yamamoto, Satoshi Astrophysics of Galaxies Solar and Stellar Astrophysics Deuterium fractionation in the closest vicinity of a protostar is important in understanding its potential heritage to a planetary system. Here, we have detected the spectral line emission of CH3OH and its three deuterated species, CH2DOH, CHD2OH, and CH3OD, toward the low-mass protostellar source B335 at a resolution of 0.''03 (5 au) with Atacama Large Millimeter/submillimeter Array. They have a ring distribution within the radius of 24 au with the intensity depression at the continuum peak. We derive the column densities and abundance ratios of the above species at 6 positions in the disk/envelope system as well as the continuum peak. The D/H ratio of CH3OH is ~[0.03-0.13], which is derived by correcting the statistical weight of 3 for CH2DOH. The [CHD2OH]/[CH2DOH] ratio is derived to be higher ([0.14-0.29]). On the other hand, the [CH2DOH]/[CH3OD] ratio ([4.9-15]) is higher than the statistical ratio of 3, and is comparable to those reported for other low-mass sources. We study the physical structure on a few au scale in B335 by analyzing the CH3OH (183,15-182,16, A) and HCOOH (120,12-110,11) line emission. Velocity structures of these lines are reasonably explained as the infalling-rotating motion. The protostellar mass and the upper limit to centrifugal barrier are thus derived to be 0.03-0.07 M_{\odot} and <7 au, respectively, showing that B335 harbors a young protostar with a tiny disk structure. Such youth of the protostar may be related to the relatively high [CH2DOH]/[CH3OH] ratio. |
| title | CH_3OH and Its Deuterated Species in the Disk/Envelope System of the Low-Mass Protostellar Source B335 |
| topic | Astrophysics of Galaxies Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2405.16744 |