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http://hdl.handle.net/20.500.12386/25125
Titolo: | The Deuterium Fraction in Massive Starless Cores and Dynamical Implications | Autori: | Kong, Shuo Tan, Jonathan C. Caselli, Paola FONTANI, FRANCESCO Pillai, Thushara Butler, Michael J. Shimajiri, Yoshito Nakamura, Fumitaka Sakai, Takeshi |
Data pubblicazione: | 2016 | Rivista: | THE ASTROPHYSICAL JOURNAL | Numero: | 821 | Fascicolo: | 2 | Da pagina:: | 94 | Abstract: | We study deuterium fractionation in two massive starless/early-stage cores, C1-N and C1-S, in Infrared Dark Cloud G028.37+00.07, which was first identified by Tan et al. with ALMA. Line emission from multiple transitions of N<SUB>2</SUB>H<SUP>+</SUP> and N<SUB>2</SUB>D<SUP>+</SUP> were observed with the ALMA, CARMA, SMA, JCMT, NRO 45 m, and IRAM 30 m telescopes. By simultaneously fitting the spectra, we estimate the excitation conditions and deuterium fraction, {D}<SUB>{frac</SUB>}<SUP>{{{N</SUP>}}<SUB>2</SUB>{{{H}}}<SUP>+</SUP>} \equiv \quad [{{{N}}}<SUB>2</SUB>{{{D}}}<SUP>+</SUP>]/[{{{N}}}<SUB>2</SUB>{{{H}}}<SUP>+</SUP>], with values of {D}<SUB>{frac</SUB>}<SUP>{{{N</SUP>}}<SUB>2</SUB>{{{H}}}<SUP>+</SUP>} ≃ 0.2-0.7, several orders of magnitude above the cosmic [D]/[H] ratio. Additional observations of o-H<SUB>2</SUB>D<SUP>+</SUP> are also presented that help constrain the ortho-to-para ratio of H<SUB>2</SUB>, which is a key quantity affecting the degree of deuteration. We then present chemodynamical modeling of the two cores, especially exploring the implications for the collapse rate relative to free-fall, α<SUB>ff</SUB>. In order to reach the high level of observed deuteration of {{{N}}}<SUB>2</SUB>{{{H}}}<SUP>+</SUP>, we find that the most likely evolutionary history of the cores involves collapse at a relatively slow rate, ≲ one-tenth of free-fall. | URI: | http://hdl.handle.net/20.500.12386/25125 | URL: | https://iopscience.iop.org/article/10.3847/0004-637X/821/2/94 | ISSN: | 0004-637X | DOI: | 10.3847/0004-637X/821/2/94 | Bibcode ADS: | 2016ApJ...821...94K | Fulltext: | open |
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