Deuterium chemistry in the Orion Bar PDR

Parise, B.; Leurini, S.; Schilke, P.; Roueff, E.; Thorwirth, Sven; Lis, D. C.

doi:10.1051/0004-6361/200912774

Cited by 80 publications

(99 citation statements)

References 54 publications

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“…Our model calculations are in the range determined by Parise et al (2009) and indicates that, in general, fully depleted cores have a lower deuterium fraction (∼ 0.1 − 0.7%) than partially depleted cores (∼ 0.8 − 1.2%). A chemical analysis shows that the rate of formation of DCN is higher in regions with full depletion compared to those with partial depletion.…”

Section: Impact Of Varying the Depletion Efficiencysupporting

confidence: 60%

Deuterium chemistry of dense gas in the vicinity of low-mass and massive star-forming regions

Awad

Viti

Bayet

et al. 2014

Monthly Notices of the Royal Astronomical Society

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The standard interstellar ratio of deuterium to hydrogen (D/H) atoms is ∼ 1.5×10 −5 . However, the deuterium fractionation is in fact found to be enhanced, to different degrees, in cold, dark cores, hot cores around massive star forming regions, lukewarm cores, and warm cores (hereafter, hot corinos) around low-mass star forming regions. In this paper, we investigate the overall differences in the deuterium chemistry between hot cores and hot corinos. We have modelled the chemistry of dense gas around low-mass and massive star forming regions using a gas-grain chemical model. We investigate the influence of varying the core density, the depletion efficiency of gaseous species on to dust grains, the collapse mode and the final mass of the protostar on the chemical evolution of star forming regions. We find that the deuterium chemistry is, in general, most sensitive to variations of the depletion efficiency on to grain surfaces, in agreement with observations. In addition, the results showed that the chemistry is more sensitive to changes in the final density of the collapsing core in hot cores than in hot corinos. Finally, we find that ratios of deuterated sulphur bearing species in dense gas around hot cores and corinos may be good evolutionary indicators in a similar way as their non deuterated counterparts.

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Section: Impact Of Varying the Depletion Efficiencysupporting

confidence: 60%

Deuterium chemistry of dense gas in the vicinity of low-mass and massive star-forming regions

Awad

Viti

Bayet

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…This result confirms the theoretical prediction that the deuterated fraction (column density ratio between a deuterated molecule and its hydrogenated counterpart, D frac ) decreases with the core evolution after the YSO formed (Caselli 2002). The high D frac found in our sources is likely because the abundances of deuterated molecules were enhanced in cold molecular clouds before the formation of the protostar or warm deuterium chemistry derived by CH 2 D + and/or C 2 HD + (Parise et al 2009). These ratios are summarized in Table 2.…”

Section: D/hsupporting

confidence: 90%

“…The millimetre wavelength window is important for studying massive star formation, because it contains many useful molecular probes, such as shock tracers (SiO, SO, HNCO and H 2 CO; Schilke et al 1997;Esplugues et al 2013;Rizzo, Fuente & García-Burillo 2005), long carbon chain molecules (c-C 3 H 2 , HC 3 N and HC 5 N; Morris, Snell & vanden Bout 1977;Chung, Osamu & Masaki 1991;Bergin, Snell & Goldsmith 1996), deuterated molecules (DCN, DCO + , C 2 D and NH 2 D; Shah & Wootten 2001;Pety et al 2007;Parise et al 2009) and dense gas traces (HCN, HCO + , CS and C 2 H; Padovani et al 2009), etc.…”

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confidence: 99%

Millimetre spectral line mapping observations towards four massive star-forming H ii regions

Wang

Zhang

et al. 2017

Mon. Not. R. Astron. Soc.

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We present spectral line mapping observations towards four massive star-forming regionsCepheus A, DR21S, S76E and G34.26+0.15 -with the IRAM 30-m telescope at the 2 and 3 mm bands. In total, 396 spectral lines from 51 molecules, one helium recombination line, 10 hydrogen recombination lines and 16 unidentified lines were detected in these four sources. An emission line of nitrosyl cyanide (ONCN, 14 0, 14 -13 0, 13 ) was detected in G34.26+0.15, as the first detection in massive star-forming regions. We found that c-C 3 H 2 and NH 2 D show enhancement in shocked regions, as suggested by the evidence of SiO and/or SO emission. The column density and rotational temperature of CH 3 CN were estimated with the rotational diagram method for all four sources. Isotope abundance ratios of 12 C/ 13 C were derived using HC 3 N and its 13 C isotopologue, which were around 40 in all four massive star-forming regions and slightly lower than the local interstellar value (∼65). The 14 N/ 15 N and 16 O/ 18 O abundance ratios in these sources were also derived using the double isotopic method, which were slightly lower than in the local interstellar medium. Except for Cep A, the 33 S/ 34 S ratios in the other three targets were derived, which were similar to that in the local interstellar medium. The column density ratios of N(DCN)/N(HCN) and N(DCO + )/N(HCO + ) in these sources were more than two orders of magnitude higher than the elemental [D]/[H] ratio, which is 1.5 × 10 −5 . Our results show that the later stage sources, G34.26+0.15 in particular, present more molecular species than earlier stage sources. Evidence of shock activity is seen in all stages studied.

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“…The steady-state model work presented here includes the updates and modifications of Parise et al (2009), and we have used it to predict relevant D/H ratios for H 2 CO and N 2 H + . The models are shown in Fig.…”

Section: Gas-phase Chemistry Modelsmentioning

confidence: 99%

“…For H 2 CO, the situation was less clear and a formation path involving gas-phase reactions could not be ruled out. In fact, for the warmer Orion Bar PDR region, Parise et al (2009) very recently advocated that gas-phase chemistry is entirely responsible for the deuterium fractionation seen for some singly deuterated species (including HDCO). It should be noted that A&A 527, A39 (2011) singly-deuterated species have been detected in dark and translucent clouds (Turner 2001) where the deuteration occurs only in the dense parts.…”

Section: Introductionmentioning

confidence: 99%

Deuterated formaldehyde inρOphiuchi A

Bergman

Parise

Liseau

et al. 2011

A&A

Self Cite

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Context. Formaldehyde is an organic molecule that is abundant in the interstellar medium. High deuterium fractionation is a common feature in low-mass star-forming regions. Observing several isotopologues of molecules is an excellent tool for understanding the formation paths of the molecules. Aims. We seek an understanding of how the various deuterated isotopologues of formaldehyde are formed in the dense regions of lowmass star formation. More specifically, we adress the question of how the very high deuteration levels (several orders of magnitude above the cosmic D/H ratio) can occur using H 2 CO data of the nearby ρ Oph A molecular cloud. Methods. From mapping observations of H 2 CO, HDCO, and D 2 CO, we have determined how the degree of deuterium fractionation changes over the central 3 × 3 region of ρ Oph A. The multi-transition data of the various H 2 CO isotopologues, as well as from other molecules (e.g., CH 3 OH and N 2 D + ) present in the observed bands, were analysed using both the standard type rotation diagram analysis and, in selected cases, a more elaborate method of solving the radiative transfer for optically thick emission. In addition to molecular column densities, the analysis also estimates the kinetic temperature and H 2 density. Results. Toward the SM1 core in ρ Oph A, the H 2 CO deuterium fractionation is very high. In fact, the observed D 2 CO/HDCO ratio is 1.34 ± 0.19, while the HDCO/H 2 CO ratio is 0.107 ± 0.015. This is the first time, to our knowledge, that the D 2 CO/HDCO abundance ratio is observed to be greater than 1. The kinetic temperature is in the range 20−30 K in the cores of ρ Oph A, and the H 2 density is (6−10) × 10 5 cm −3 . We estimate that the total H 2 column density toward the deuterium peak is (1−4) × 10 23 cm −2 . As depleted gas-phase chemistry is not adequate, we suggest that grain chemistry, possibly due to abstraction and exchange reactions along the reaction chain H 2 CO → HDCO → D 2 CO, is at work to produce the very high deuterium levels observed.

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Deuterium chemistry in the Orion Bar PDR

Cited by 80 publications

References 54 publications

Deuterium chemistry of dense gas in the vicinity of low-mass and massive star-forming regions

Deuterium chemistry of dense gas in the vicinity of low-mass and massive star-forming regions

Millimetre spectral line mapping observations towards four massive star-forming H ii regions

Deuterated formaldehyde inρOphiuchi A

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