Testing grain surface chemistry: a survey of deuterated formaldehyde and methanol in low-mass class 0 protostars

Parise, B.; Ceccarelli, C.; Tielens, A. G. G. M.; Castets, A.; Caux, E.; Leflóch, B.; Maret, S.

doi:10.1051/0004-6361:20054476

Cited by 170 publications

(276 citation statements)

References 29 publications

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“…Sakai et al (2009b) observed many deuterated carbon-chain molecules, and found that the deuterium fractionation ratios are moderate (2-7 %). The CH 2 DOH/CH 3 OH ratio is derived to be lower than 3 %, which is much lower than that found in hot corinos (Parise et al 2006). The observed ratios mean less degree of the CO depletion, which is consistent with the short time scale of the starless-core phase.…”

Section: Origin Of the Different Mantle Compositionssupporting

confidence: 68%

Observations of Complex Molecules in Low-Mass Protostars

Sakai

Yamamoto

2011

Proc. IAU

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Abstract. Low-mass star forming regions are rich inventories of complex organic molecules. Furthermore, they show significant chemical diversity even among sources in a similar physical evolutionary stage (i.e. Class 0 sources). One distinct case is the hot corino chemistry characterized by rich existence of saturated complex organic molecules such as HCOOCH3 and C2 H5 CN, whereas the other is the warm carbon-chain chemistry (WCCC) characterized by extraordinary richness of unsaturated complex organic molecules such as carbon-chain molecules. We here summarize these observational achievements during the last decade, and present a unified picture of carbon chemistry in low-mass protostellar cores. The chemical diversity most likely originates from the source-to-source difference in chemical compositions of grain mantles. In particular, the gas-phase abundance of CH 4 evaporated from grain mantles is thought to be a key factor for appearance of WCCC. The origin of the diversity and its evolution to protopranetary disks are discussed.

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Section: Origin Of the Different Mantle Compositionssupporting

confidence: 68%

Observations of Complex Molecules in Low-Mass Protostars

Sakai

Yamamoto

2011

Proc. IAU

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“…2, we have plotted the [CH 2 DOH]/[CH 3 OD] ratio as a function of the luminosity of the protostars for all the sources (except G24.78+0.08) where this ratio has been measured so far. In addition to the present observations, we have thus included a sample of low-mass protostars (Parise et al 2006), as well as the hot-core Orion IRc2 (Jacq et al 1993 Parise et al (2006), while the data for Orion IRc2 is from Jacq et al (1993). The upper limit reported in Table 1 for G24.78+0.08 is not plotted because of the uncertain identification of the CH 3 OD line at 133.9254 GHz.…”

Section: Discussionmentioning

confidence: 99%

“…Parise et al 2006), a property observed in several other deuterated molecules in low mass protostars, although to a lesser extent (Ceccarelli et al 2007). This large deuteration very likely implies that, in low mass protostars, methanol was formed during the pre-collapse, cold, and dense phase.…”

Section: Introductionmentioning

confidence: 90%

The puzzling deuteration of methanol in low- to high-mass protostars

Ratajczak

Taquet

Kahane

et al. 2011

A&A

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Context. The current theory of methanol deuteration on interstellar grains predicts that the abundance ratio of the singly deuterated isotopologues [ OD] ratios are inconsistent with the current theory of methanol deuteration, independently of the mass of the source. While the large ratios measured in low-and intermediate-mass sources can be explained qualitatively by various selective depletion mechanisms, the small ratios (<2) measured toward massive hot cores are puzzling. A revision of the deuterium chemistry in hot cores is suggested.

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“…Methanol deuteration is thus likely to be produced completely by active grain-surface chemistry, controlled by the atomic D content of the accreting gas. The high atomic D/H ratio required to account for the observed fractionation (0.1-0.2, Parise et al 2002) has been explained by invoking an efficient transfer of atomic deuterium from the HD main reservoir via the intermediate H 2 D + /D 2 H + ions (Roberts et al 2003;Parise et al 2006), which are very abundant in the CO-depleted pre-stellar gas (e.g., Caselli et al 2003;Phillips & Vastel 2003;Vastel et al 2004;Parise et al 2011). Presently, all the measured methanol deuterations have been satisfactorily reproduced by the most recent coupled gas-grain models (Taquet et al 2012;Aikawa et al 2012), Article published by EDP Sciences A27, page 1 of 8 thus supporting the hypothesis that D-fractionation in methanol is a distinctive relic of the protostars' past history.…”

Section: Introductionmentioning

confidence: 99%

Deuterated methanol in the pre-stellar core L1544

Bizzocchi

Caselli

Spezzano

et al. 2014

A&A

103

152

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Context. High methanol (CH 3 OH) deuteration has been revealed in Class 0 protostars with the detection of singly, doubly, and even triply D-substituted forms. Methanol is believed to form during the pre-collapse phase via gas-grain chemistry and then eventually injected into the gas when the heating produced by the newly formed protostar sublimates the grain mantles. The molecular deuterium fraction of the warm gas is thus a relic of the cold pre-stellar era and provides hints of the past history of the protostars. Aims. Pre-stellar cores represent the preceding stages in the process of star formation. We aim at measuring methanol deuteration in L1544, a prototypical dense and cold core on the verge of gravitational collapse. The aim is to probe the deuterium fractionation process while the "frozen" molecular reservoir is accumulated onto dust grains. Methods. Using the IRAM 30 m telescope, we mapped the methanol emission in the pre-stellar core L1544 and observed singly deuterated methanol (CH 2 DOH and CH 3 OD) towards the dust peak of L1544. Non-LTE radiative transfer modelling was performed on three CH 3 OH emissions lines at 96.7 GHz, using a Bonnor-Ebert sphere as a model for the source. We have also assumed a centrally decreasing abundance profile to take the molecule freeze-out in the inner core into account. The column density of CH 2 DOH was derived assuming LTE excitation and optically thin emission. Results. The CH 3 OH emission has a highly asymmetric morphology, resembling a non-uniform ring surrounding the dust peak, where CO is mainly frozen onto dust grains. The observations provide an accurate measure of methanol deuteration in the cold pre-stellar gas. The derived abundance ratio is [CH 2 DOH]/[CH 3 OH] = 0.10 ± 0.03, which is significantly smaller than the ones found in lowmass Class 0 protostars and smaller than the deuterium fraction measured in other molecules towards L1544. The singly-deuterated form CH 3 OD was not detected at 3σ sensitivity of 7 mK km s −1 , yielding a lower limit of [CH 2 DOH]/[CH 3 OD] ≥ 10, consistent with previous measurements towards Class 0 protostars. Conclusions. The low deuterium fractionation observed in L1544 and the morphology of the CH 3 OH emission suggest that we are mainly tracing the outer parts of the core, where CO just started to freeze-out onto dust grains.

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Testing grain surface chemistry: a survey of deuterated formaldehyde and methanol in low-mass class 0 protostars

Cited by 170 publications

References 29 publications

Observations of Complex Molecules in Low-Mass Protostars

Observations of Complex Molecules in Low-Mass Protostars

The puzzling deuteration of methanol in low- to high-mass protostars

Deuterated methanol in the pre-stellar core L1544

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