Issue |
A&A
Volume 666, October 2022
|
|
---|---|---|
Article Number | A191 | |
Number of page(s) | 19 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/202243459 | |
Published online | 28 October 2022 |
Confirmation of the outflow in L1451-mm: SiO line and CH3OH maser detections★,★★
1
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS,
B18N, allée Geoffroy Saint-Hilaire,
33615
Pessac, France
e-mail: valentine.wakelam@u-bordeaux.fr
2
Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, UPS-OMP, CNRS, CNES,
9 av. du Colonel Roche,
31028
Toulouse Cedex 4, France
3
European Spallation Source ERIC,
PO Box 176,
221 00
Lund, Sweden
Received:
3
March
2022
Accepted:
1
August
2022
Context. The observational counterparts of theoretically predicted first hydrostatic cores (FHSC) have been searched for in the interstellar medium for nearly two decades now. Distinguishing them from other types of more evolved but still embedded objects remains a challenge because these objects have a short lifetime, are small, and embedded in a dense cocoon. One possible lead to finding them is the characterization of the outflows that are launched by these objects, which are assumed to have a low velocity and be small extent.
Aims. We observed the L1451-mm FHSC candidate with the NOEMA interferometer (and complementary IRAM 30m data) in order to study the emission of several molecules.
Methods. Molecular lines were reduced and analyzed with the GILDAS package network, the CASSIS software, and some python packages. A nonlocal thermodynamic equilibrium analysis of the CH3OH detected lines was performed to retrieve the physical conditions of the emitting region around the central source, together with the CH3OH, SiO, CS, and H2CO column densities.
Results. Of the targeted molecules, we detected lines of c-C3H2, CH3OH, CS, C34S, SO, DCN, DCO+, H2CO, HC3N, HDCO, and SiO. One of the methanol lines appears to be a maser line. The detection of this class I maser and the SiO line in L1451-mm support the presence of a low-velocity and compact outflow. The excitation conditions of the thermal lines of methanol are also compatible with shocks (H2 density of ~3 × 106 cm−3 and a temperature higher than 40 K).
Conclusions. Although these low-velocity outflows are theoretically predicted by some models of FHSC, these models also predict the shock temperature to be below 20 K, that is, not evaporating methanol. In addition, the predicted velocities would not erode the grains and release silicon in the gas phase. We therefore conclude that these new observations favor the hypothesis that L1451-mm would be at a very early protostellar stage, launching an outflow nearly on the plane of the sky with a higher velocity than is observed.
Key words: astrochemistry / stars: protostars / ISM: molecules / ISM: individual objects: L1451-mm / stars: low-mass
The reduced datacubes used for this work are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/666/A191
© V. Wakelam et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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