THE HDO/H
                    <sub>2</sub>
                    O RATIO IN GAS IN THE INNER REGIONS OF A LOW-MASS PROTOSTAR

Jørgensen, J. K.; Dishoeck, E. F. van

doi:10.1088/2041-8205/725/2/l172

Cited by 43 publications

(61 citation statements)

References 26 publications

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“…The deuteration fraction observed in high-mass hot cores is typically HDO/H 2 O ≤ 10 −3 (Jacq et al 1990;Gensheimer et al 1996;Helmich et al 1996), although higher values (∼10 −2 ) have recently been found for Orion (Persson et al 2007;Bergin et al 2010). This ratio has also been estimated in the inner envelope of low-mass protostars such as IRAS 16293-2422 (Parise et al 2005) at about 3%, NGC 1333-IRAS4B (Jørgensen & van Dishoeck 2010) with an upper limit of 0.06%, and NGC 1333-IRAS2A (Liu et al 2011) with a lower limit of 1%. Deuterated water has also been sought in ices towards several protostars, and has allowed Dartois et al (2003) and Parise et al (2003) to obtain upper limits of solid HDO/H 2 O from 0.5% to 2%.…”

Section: Introductionmentioning

confidence: 68%

“…However, this ratio of a few percent does not seem typical of all the Class 0 protostars since an upper limit of 6 × 10 −4 has been determined in the inner part of the envelope of the lowmass protostar NGC 1333-IRAS4B (Jørgensen & van Dishoeck 2010). The determination of the water deuterium fractionation in a larger sample of Class 0 protostars would allow us to know, from a statistical point of view, whether the HDO/H 2 O ratio is A132, page 10 of 12 rather about 10 −4 −10 −3 as observed in the NGC 1333-IRAS4B protostar, in comets (∼3 × 10 −4 ; e.g.…”

Section: Discussionmentioning

confidence: 93%

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A study of deuterated water in the low-mass protostar IRAS 16293-2422

Coutens¹,

Vastel²,

Caux³

et al. 2012

A&A

133

236

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Context. Water is a primordial species in the emergence of life, and comets may have brought a large fraction to Earth to form the oceans. To understand the evolution of water from the first stages of star formation to the formation of planets and comets, the HDO/H 2 O ratio is a powerful diagnostic. Aims. Our aim is to determine precisely the abundance distribution of HDO towards the low-mass protostar IRAS 16293-2422 and learn more about the water formation mechanisms by determining the HDO/H 2 O abundance ratio. Results. It is the first time that so many HDO and H 182 O transitions have been detected towards the same source with high spectral resolution. We derive an inner HDO abundance (T ≥ 100 K) of about 1.7 × 10 −7 and an outer HDO abundance (T < 100 K) of about 8 × 10 −11 . To reproduce the HDO absorption lines observed at 894 and 465 GHz, it is necessary to add an absorbing layer in front of the envelope. It may correspond to a water-rich layer created by the photodesorption of the ices at the edges of the molecular cloud. At a 3σ uncertainty, the HDO/H 2 O ratio is 1.4-5.8% in the hot corino, whereas it is 0.2-2.2% in the outer envelope. It is estimated at ∼4.8% in the added absorbing layer. Conclusions. Although it is clearly higher than the cosmic D/H abundance, the HDO/H 2 O ratio remains lower than the D/H ratio derived for other deuterated molecules observed in the same source. The similarity of the ratios derived in the hot corino and in the added absorbing layer suggests that water formed before the gravitational collapse of the protostar, contrary to formaldehyde and methanol, which formed later once the CO molecules had depleted on the grains.

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Section: Introductionmentioning

confidence: 68%

Section: Discussionmentioning

confidence: 93%

A study of deuterated water in the low-mass protostar IRAS 16293-2422

Coutens¹,

Vastel²,

Caux³

et al. 2012

A&A

133

236

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“…Study (1) Inner HDO/H 2 O ratio Outer HDO/H 2 O ratio Observations (2) Modeling (3) IRAS 16293-2422 a 3 × 10 −2 ≤2 × 10 −3 HDO: IRAM (4), JCMT (1) 1D, non-LTE H 16 2 O: ISO (11) b 4 × 10 −3 -5.1 × 10 −2 3 × 10 −3 -1.5 × 10 −2 HDO: HIFI (9), IRAM (3), JCMT (1) 1D, non-LTE H 18 2 O: HIFI (5) Jørgensen & van Dishoeck (2010a). (2) This column shows which tracers are used to determine the HDO/H 2 O ratios, which telescopes the analysis is based on, and how many detected lines (number into brackets) of each tracer are used.…”

Section: Sourcementioning

confidence: 99%

“…The notation IRAM refers to the single-dish 30 m-telescope. The star ( * ) shows that the modeling of the water lines was not carried out in the study quoted in Col. 2, but come, as explained in the text, from the following papers: Jørgensen & van Dishoeck (2010a); Persson et al (2012); Taquet et al (2013a); Mottram et al (2013). (3) This column describes the type of modeling used to determine the HDO/H 2 O ratio: 0D or 1D structure and LTE or non-LTE analysis.…”

Section: Sourcementioning

confidence: 99%

“…In NGC 1333 IRAS 4A (hereafter IRAS 4A) and NGC 1333 IRAS 4B (hereafter IRAS 4B), fewer studies have been carried out and are only based on interferometric observations. In IRAS 4A, Taquet et al (2013a) found a ratio of 5 × 10 −3 −3 × 10 −2 , and in IRAS 4B, Jørgensen & van Dishoeck (2010a) derived an upper limit of ∼6 × 10 −4 . For more details on the results of the different studies of HDO/H 2 O ratios in Class 0 sources and their type of analysis, we refer the reader to Table 4 and Sect.…”

Section: Introductionmentioning

confidence: 98%

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Deuterated water in the solar-type protostars NGC 1333 IRAS 4A and IRAS 4B

Coutens

Vastel

Cabrit

et al. 2013

A&A

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Context. The measure of the water deuterium fractionation is a relevant tool for understanding mechanisms of water formation and evolution from the prestellar phase to the formation of planets and comets. Aims. The aim of this paper is to study deuterated water in the solar-type protostars NGC 1333 IRAS 4A and IRAS 4B, to compare their HDO abundance distributions with other star-forming regions, and to constrain their HDO/H 2 O abundance ratios. Methods. Using the Herschel/HIFI instrument as well as ground-based telescopes, we observed several HDO lines covering a large excitation range (E up /k = 22-168 K) towards these protostars and an outflow position. Non-local thermal equilibrium radiative transfer codes were then used to determine the HDO abundance profiles in these sources. Results. The HDO fundamental line profiles show a very broad component, tracing the molecular outflows, in addition to a narrower emission component and a narrow absorbing component. In the protostellar envelope of NGC 1333 IRAS 4A, the HDO inner (T ≥ 100 K) and outer (T < 100 K) abundances with respect to H 2 are estimated with a 3σ uncertainty at 7.5 +3.5 −3.0 × 10 −9 and 1.2 +0.4 −0.4 × 10 −11 , respectively, whereas in NGC 1333 IRAS 4B they are 1 +1.8 −0.9 × 10 −8 and 1.2 +0.6 −0.4 × 10 −10 , respectively. Similarly to the low-mass protostar IRAS 16293-2422, an absorbing outer layer with an enhanced abundance of deuterated water is required to reproduce the absorbing components seen in the fundamental lines at 465 and 894 GHz in both sources. This water-rich layer is probably extended enough to encompass the two sources, as well as parts of the outflows. In the outflows emanating from NGC 1333 IRAS 4A, the HDO column density is estimated at about (2-4) × 10 13 cm −2 , leading to an abundance of about (0.7-1.9) × 10 −9 . An HDO/H 2 O ratio between 7 × 10 −4 and 9 × 10 −2 is also derived in the outflows. In the warm inner regions of these two sources, we estimate the HDO/H 2 O ratios at about 1 × 10 −4 -4 × 10 −3 . This ratio seems higher (a few %) in the cold envelope of IRAS 4A, whose possible origin is discussed in relation to formation processes of HDO and H 2 O. Conclusions. In low-mass protostars, the HDO outer abundances range in a small interval, between ∼10 −11 and a few 10 −10 . No clear trends are found between the HDO abundance and various source parameters (L bol , L smm , L smm /L bol , T bol , L 0.6 bol /M env ). A tentative correlation is observed, however, between the ratio of the inner and outer abundances with the submillimeter luminosity.

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