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

J Molet,F Herpin,T Nony,D Despois,S Bontemps,F Motte,N Brouillet,A Gusdorf,F Louvet

doi:10.1051/0004-6361/201935497

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.

Highlights

Understanding high-mass stars (M > 8 M ) is crucial in modern astrophysics since their energy budget towards the interstellar medium is the most important contribution coming from stars.They form in massive dense cores of ∼100 M within ∼0.1 pc (Motte et al 2007; Bontemps et al 2010), by processes far less understood than for low-mass stars
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
The first model supposes the existence of starless massive dense cores, whereas, for the second one, low-mass prestellar cores can become high-mass protostars by collecting surrounding gas

Summary

Introduction

Understanding high-mass stars (M > 8 M ) is crucial in modern astrophysics since their energy budget towards the interstellar medium is the most important contribution coming from stars. They form in massive dense cores of ∼100 M within ∼0.1 pc (Motte et al 2007; Bontemps et al 2010), by processes far less understood than for low-mass stars. The first model supposes the existence of starless massive dense cores, whereas, for the second one, low-mass prestellar cores can become high-mass protostars by collecting surrounding gas. The observation of a high-mass prestellar core is challenging due to the lower number of high-mass stars compared to the number of low-mass stars (only ∼1% of the Galactic stellar population) and the short duration of the hypothetical prestellar phase (∼104 −105 yr; Tigé et al 2017, and references therein). Motte et al (2018a) and Louvet (2018) list the current high-mass prestellar core candidates: CygX-N53-MM2

Methods

Results

Conclusion