THE DEUTERIUM FRACTIONATION TIMESCALE IN DENSE CLOUD CORES: A PARAMETER SPACE EXPLORATION

Shuo Kong Paola Caselli 1 Jonathan C. Tan 2 Valentine Wakelam 3 Olli Sipilä
3 AMOR 2015
LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac], UB - Université de Bordeaux, INSU - CNRS - Institut national des sciences de l'Univers , CNRS - Centre National de la Recherche Scientifique
Abstract : The deuterium fraction, [N2D+]/[N2H+], may provide information about the ages of dense, cold gas structures, which are important for comparing dynamical models of cloud core formation and evolution. Here we introduce a complete chemical network with species containing up to three atoms, with the exception of the oxygen chemistry, where reactions involving H3O+ and its deuterated forms have been added, significantly improving the consistency with comprehensive chemical networks. Deuterium chemistry and spin states of H2 and H3+ isotopologues are included in this primarily gas-phase chemical model. We investigate the dependence of deuterium chemistry on these model parameters: density ({{n}H}), temperature, cosmic ray ionization rate, and gas-phase depletion factor of heavy elements ({{f}D}). We also explore the effects of time-dependent freeze-out of gas-phase species and the dynamical evolution of density at various rates relative to free-fall collapse. For a broad range of model parameters, the timescales to reach large values of Dfrac{{N2}{{H}+}}≳ 0.1, observed in some low- and high-mass starless cores, are relatively long compared to the local free-fall timescale. These conclusions are unaffected by introducing time-dependent freeze-out and considering models with evolving density, unless the initial {{f}D} ≳ 10. For fiducial model parameters, achieving Dfrac{{N2}{{H}+}}≳ 0.1 requires collapse to be proceeding at rates at least several times slower than that of free-fall collapse, perhaps indicating a dynamically important role for magnetic fields in supporting starless cores and thus the regulation of star formation.
Type de document :
Article dans une revue
Astrophysical Journal, American Astronomical Society, 2015, 804 (2), pp.id. 98. 〈10.1088/0004-637X/804/2/98〉
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Contributeur : Marie-Paule Pomies <>
Soumis le : jeudi 5 décembre 2013 - 11:36:44
Dernière modification le : dimanche 15 octobre 2017 - 22:44:05

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Shuo Kong, Paola Caselli, Jonathan C. Tan, Valentine Wakelam, Olli Sipilä. THE DEUTERIUM FRACTIONATION TIMESCALE IN DENSE CLOUD CORES: A PARAMETER SPACE EXPLORATION. Astrophysical Journal, American Astronomical Society, 2015, 804 (2), pp.id. 98. 〈10.1088/0004-637X/804/2/98〉. 〈hal-00914300〉

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