Hunting for hot corinos and WCCC sources in the OMC-2/3 filament

¹ Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 38000 Grenoble, France
e-mail: mathilde.bouvier@univ-grenoble-alpes.fr
² Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin-D’Hères, France
³ CNRS, IPAG, 38000 Grenoble, France
⁴ Department of Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
⁵ RIKEN, Cluster for Pioneering Research, 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan
⁶ Research Center for the Early Unvierse, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
⁷ Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218-2685, USA

Received: 21 November 2019
Accepted: 3 March 2020

Abstract

Context. Solar-like protostars are known to be chemically rich, but it is not yet clear how much their chemical composition can vary and why. So far, two chemically distinct types of Solar-like protostars have been identified: hot corinos, which are enriched in interstellar Complex Organic Molecules, such as methanol (CH₃OH) or dimethyl ether (CH₃OCH₃), and warm carbon chain chemistry (WCCC) objects, which are enriched in carbon chain molecules, such as butadiynyl (C₄H) or ethynyl radical (CCH). However, none of these have been studied so far in environments similar to that in which our Sun was born, that is, one that is close to massive stars.

Aims. In this work, we search for hot corinos and WCCC objects in the closest analogue to the Sun’s birth environment, the Orion Molecular Cloud 2/3 (OMC-2/3) filament located in the Orion A molecular cloud.

Methods. We obtained single-dish observations of CCH and CH₃OH line emission towards nine Solar-like protostars in this region. As in other similar studies of late, we used the [CCH]/[CH₃OH] abundance ratio in order to determine the chemical nature of our protostar sample.

Results. Unexpectedly, we found that the observed methanol and ethynyl radical emission (over a few thousands au scale) does not seem to originate from the protostars but rather from the parental cloud and its photo-dissociation region, illuminated by the OB stars of the region.

Conclusions. Our results strongly suggest that caution should be taken before using [CCH]/[CH₃OH] from single-dish observations as an indicator of the protostellar chemical nature and that there is a need for other tracers or high angular resolution observations for probing the inner protostellar layers.