Lykke, J. M., Coutens, A., Jorgensen, J. K., van der Wiel, M. H. D., Garrod, R. T., Mueller, H. S. P., Bjerkeli, P., Bourke, T. L., Calcutt, H., Drozdovskaya, M. N., Favre, C., Fayolle, E. C., Jacobsen, S. K., Oberg, K. I., Persson, M. V., van Dishoeck, E. F. and Wampfler, S. F. (2017). The ALMA-PILS survey: First detections of ethylene oxide, acetone and propanal toward the low-mass protostar IRAS 16293-2422. Astron. Astrophys., 597. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Context. One of the open questions in astrochemistry is how complex organic and prebiotic molecules are formed. The unsurpassed sensitivity of the Atacama Large Millimeter/submillimeter Array (ALMA) takes the quest for discovering molecules in the warm and dense gas surrounding young stars to the next level. Aims. Our aim is to start the process of compiling an inventory of oxygen-bearing complex organic molecules toward the solar-type Class 0 protostellar binary IRAS 16293-2422 from an unbiased spectral survey with ALMA, Protostellar Interferometric Line Survey (PILS). Here we focus on the new detections of ethylene oxide (c-C2H4O), acetone (CH3COCH3), and propanal (C2H5CHO). Methods. With ALMA, we surveyed the spectral range from 329 to 363 GHz at 0.5 '' (60 AU diameter) resolution. Using a simple model for the molecular emission in local thermodynamical equilibrium, the excitation temperatures and column densities of each species were constrained. Results. We successfully detect propanal (44 lines), ethylene oxide (20 lines) and acetone (186 lines) toward one component of the protostellar binary, IRAS 16293B. The high resolution maps demonstrate that the emission for all investigated species originates from the compact central region close to the protostar. This, along with a derived common excitation temperature of T-ex approximate to 125 K, is consistent with a coexistence of these molecules in the same gas. Conclusions. The observations mark the first detections of acetone, propanal and ethylene oxide toward a low-mass protostar. The relative abundance ratios of the two sets of isomers, a CH3COCH3/C2H5CHO ratio of 8 and a CH3CHO/c-C2H4O ratio of 12, are comparable to previous observations toward high-mass protostars. The majority of observed abundance ratios from these results as well as those measured toward high-mass protostars are up to an order of magnitude above the predictions from chemical models. This may reflect either missing reactions or uncertain rates in the chemical networks. The physical conditions, such as temperatures or densities, used in the models, may not be applicable to solar-type protostars either.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Lykke, J. M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Coutens, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Jorgensen, J. K.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
van der Wiel, M. H. D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Garrod, R. T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Mueller, H. S. P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Bjerkeli, P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Bourke, T. L.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Calcutt, H.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Drozdovskaya, M. N.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Favre, C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Fayolle, E. C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Jacobsen, S. K.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Oberg, K. I.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Persson, M. V.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
van Dishoeck, E. F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Wampfler, S. F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-248271
DOI: 10.1051/0004-6361/201629180
Journal or Publication Title: Astron. Astrophys.
Volume: 597
Date: 2017
Publisher: EDP SCIENCES S A
Place of Publication: LES ULIS CEDEX A
ISSN: 1432-0746
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
STAR-FORMING REGIONS; SOLAR-TYPE PROTOSTAR; HOT CORE; INTERSTELLAR ACETONE; LINE SURVEY; ORION-KL; MOLECULAR-SPECTROSCOPY; MICROWAVE-SPECTRUM; ORGANIC-MOLECULES; COLOGNE DATABASEMultiple languages
Astronomy & AstrophysicsMultiple languages
Refereed: Yes
URI: http://kups.ub.uni-koeln.de/id/eprint/24827

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