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The ALMA-PILS Surve...
The ALMA-PILS Survey: Formaldehyde deuteration in warm gas on small scales toward IRAS 16293-2422 B
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- Persson, Magnus V., 1983 (author)
- Chalmers tekniska högskola,Chalmers University of Technology,Universiteit Leiden (UL),Leiden University (UL)
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- Jørgensen, J. K. (author)
- Niels Bohr Institute
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- Müller, H. S.P. (author)
- Universität zu Köln,University of Cologne
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- Coutens, A. (author)
- Laboratoire d'Astrophysique de Bordeaux
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- Van Dishoeck, E. F. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG),Universiteit Leiden (UL),Leiden University (UL)
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- Taquet, V. (author)
- Osservatorio Astrofisico di Arcetri,Arcetri Astrophysical Observatory
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- Calcutt, Hannah, 1988 (author)
- Universiteit Leiden (UL),Leiden University (UL)
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- van der Wiel, M. H. D. (author)
- Netherlands Institute for Radio Astronomy (ASTRON)
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- Bourke, T. L. (author)
- SKA Organisation
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- Wampfler, S. F. (author)
- Universität Bern,University of Bern
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(creator_code:org_t)
- 2018-02-27
- 2018
- English.
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 610
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Abstract
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- Context. The enhanced degrees of deuterium fractionation observed in envelopes around protostars demonstrate the importance of chemistry at low temperatures, relevant in pre- and protostellar cores. Formaldehyde is an important species in the formation of methanol and more complex molecules. Aims. Here, we aim to present the first study of formaldehyde deuteration on small scales around the prototypical low-mass protostar IRAS 16293-2422 using high spatial and spectral resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the excitation temperature, abundances and fractionation level of several formaldehyde isotopologues, including its deuterated forms. Methods. Excitation temperature and column densities of formaldehyde in the gas close to one of the components of the binary were constrained through modeling of optically thin lines assuming local thermodynamical equilibrium. The abundance ratios were compared to results from previous single dish observations, astrochemical models and local ISM values. Results. Numerous isotopologues of formaldehyde are detected, among them H 2 C 17 O, and D 2 13 CO for the first time in the ISM. The large range of upper energy levels covered by the HDCO lines help constrain the excitation temperature to 106 ± 13 K. Using the derived column densities, formaldehyde shows a deuterium fractionation of HDCO/H 2 CO = 6.5 ± 1%, D 2 CO/HDCO = 12.8 -4.1 +3.3 %, and D 2 CO/H 2 CO = 0.6(4) ± 0.1%. The isotopic ratios derived are 16 O/ 18 O = 805 -79 +43 , 18 O/ 17 O = 3.2 -0.3 +0.2 , and 12 C/ 13 C = 56 -11 +8 . Conclusions. The HDCO/H 2 CO ratio is lower than that found in previous studies, highlighting the uncertainties involved in interpreting single dish observations of the inner warm regions. The D 2 CO/HDCO ratio is only slightly larger than the HDCO/H 2 CO ratio. This is consistent with formaldehyde forming in the ice as soon as CO has frozen onto the grains, with most of the deuteration happening toward the end of the prestellar core phase. A comparison with available time-dependent chemical models indicates that the source is in the early Class 0 stage.
Subject headings
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
- NATURVETENSKAP -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)
- NATURVETENSKAP -- Fysik -- Annan fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Other Physics Topics (hsv//eng)
Keyword
- Stars: protostars
- ISM: molecules
- ISM: individual objects: IRAS 16293-2422
- Stars: formation
- Astrochemistry
Publication and Content Type
- art (subject category)
- ref (subject category)
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Persson, Magnus ...
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Jørgensen, J. K.
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Müller, H. S.P.
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Coutens, A.
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Van Dishoeck, E. ...
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Taquet, V.
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show more...
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Calcutt, Hannah, ...
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van der Wiel, M. ...
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Bourke, T. L.
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Wampfler, S. F.
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NATURAL SCIENCES
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and Atom and Molecul ...
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Chalmers University of Technology