Universität zu Köln

Spezzano, S., Bizzocchi, L., Caselli, P., Harju, J. and Bruenken, S. (2016). Chemical differentiation in a prestellar core traces non-uniform illumination. Astron. Astrophys., 592. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Dense cloud cores present chemical differentiation because C-and N-bearing molecules are distributed differently, the latter being less affected by freeze-out onto dust grains. In this letter we show that two C-bearing molecules, CH3OH and c-C3H2, present a strikingly different (complementary) morphology while showing the same kinematics towards the prestellar core L1544. After comparing their distribution with the large-scale H-2 column density N(H-2) map from the Herschel satellite, we find that these two molecules trace different environmental conditions in the surrounding of L1544: the c-C3H2 distribution peaks close to the southern part of the core, where the surrounding molecular cloud has an N(H-2) sharp edge, while CH3OH mainly traces the northern part of the core, where N(H-2) presents a shallower tail. We conclude that this is evidence of chemical differentiation driven by different amounts of illumination from the interstellar radiation field: in the south, photochemistry maintains more C atoms in the gas phase, allowing carbon-chain (such as c-C3H2) production; in the north, C is mainly locked in CO, and methanol traces the zone where CO starts to freeze out significantly. During the process of cloud contraction, different gas and ice compositions are thus expected to mix towards the central regions of the core, where a potential solar-type system will form. An alternative view on carbon-chain chemistry in star-forming regions is also provided.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Spezzano, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bizzocchi, L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Caselli, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Harju, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bruenken, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-267316
DOI:	10.1051/0004-6361/201628652
Journal or Publication Title:	Astron. Astrophys.
Volume:	592
Date:	2016
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:	Keywords Language CARBON-CHAIN-CHEMISTRY; STARLESS CORES; INTERNAL STRUCTURE; PROTOSTELLAR CORE; L1544; DESORPTION; METHANOL; DUST; DYNAMICS; EVOLUTION Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/26731