Molecular analysis of a high-mass prestellar core candidate in W43-MM1

¹ Laboratoire d’astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
e-mail: jordan.molet@u-bordeaux.fr
² Université Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble, 38000 Grenoble, France
³ Laboratoire de Physique de l’École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
⁴ LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Université Paris 06, 75231 Paris, France
⁵ AIM Paris-Saclay Département d’Astrophysique, CEA, CNRS, Univ. Paris Diderot, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
⁶ Departamento de Astronomía de Chile, Universidad de Chile, Santiago, Chile

Received: 19 March 2019
Accepted: 11 May 2019

Abstract

Context. High-mass analogues of low-mass prestellar cores are searched for to constrain the models of high-mass star formation. Several high-mass cores, at various evolutionary stages, have been recently identified towards the massive star-forming region W43-MM1 and amongst them a high-mass prestellar core candidate.

Aims. We aim to characterise the chemistry in this high-mass prestellar core candidate, referred to as W43-MM1 core #6, and its environment.

Methods. Using ALMA high-spatial resolution data of W43-MM1, we have studied the molecular content of core #6 and a neighbouring high-mass protostellar core, referred to as #3, which is similar in size and mass to core #6. We first subtracted the continuum emission using a method based on the density distribution of the intensities on each pixel. Then, from the distribution of detected molecules, we identified the molecules centred on the prestellar core candidate (core #6) and those associated to shocks related to outflows and filament formation. Then we constrained the column densities and temperatures of the molecules detected towards the two cores.

Results. While core #3 appears to contain a hot core with a temperature of about 190 K, core #6 seems to have a lower temperature in the range from 20 to 90 K from a rotational diagram analysis. We have considered different source sizes for core #6 and the comparison of the abundances of the detected molecules towards the core with various interstellar sources shows that it is compatible with a core of size 1000 au with T = 20−90 K or a core of size 500 au with T ~ 80 K.

Conclusions. Core #6 of W43-MM1 remains one of the best high-mass prestellar core candidates even if we cannot exclude that it is at the very beginning of the protostellar phase of high-mass star formation.