Seeds of Life in Space (SOLIS)

VII. Discovery of a cold dense methanol blob toward the L1521F VeLLO system^★

¹ Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 38000 Grenoble, France
e-mail: cecile.favre@univ-grenoble-alpes.fr
² IRAP, Université de Toulouse, CNRS, CNES, UPS, (Toulouse), France
³ Centro de Astrobiología (CSIC, INTA), Ctra. de Torrejon a Ajalvir km4, Torrejón de Ardoz, 28850 Madrid, Spain
⁴ School of Physics and Astronomy, Queen Mary University of London, 327 Mile End Road, London, E1 4NS, UK
⁵ Max-Planck-Institut für extraterrestrische Physik (MPE), 85748 Garching, Germany
⁶ Observatorio Astronómico Nacional (OAG-IGN), Alfonso XII 3, 28014 Madrid, Spain
⁷ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Florence, Italy
⁸ Department of Physics and Astronomy, University College London, Gower Street, WC1E 6BT, London, UK
⁹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹⁰ Department of Physics, The University of Tokyo, Bunkyo-ku, 113-0033 Tokyo, Japan
¹¹ Ural Federal University, 620002, 19 Mira street, Yekaterinburg, Russia
¹² RIKEN Cluster for Pioneering Research, 2-1, Hirosawa, Wako-shi, 351-0198 Saitama, Japan
¹³ Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, Domaine Universitaire de Grenoble, 38406 Saint-Martin d’Hères, France
¹⁴ Dipartimento di Chimica, Biologia e Biotecnologie, Via Elce di Sotto 8, 06123 Perugia, Italy
¹⁵ Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain
¹⁶ LERMA, Université de Cergy-Pontoise, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC, Univ. Paris 06, 95000 Cergy Pontoise, France
¹⁷ University of AL-Muthanna, College of Science, Physics Department, AL-Muthanna, Iraq
¹⁸ Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes) – UMR 6251, 35000 Rennes, France
¹⁹ ESO, Karl Schwarzchild Srt. 2, 85478 Garching bei München, Germany
²⁰ Aix-Marseille Université, PIIM UMR-CNRS 7345, 13397 Marseille, France
²¹ Università degli Studi di Torino, Dipartimento Chimica Via Pietro Giuria 7, 10125 Torino, Italy
²² Engineering Research Institute Ventspils International Radio Astronomy Centre of Ventspils University of Applied Sciences, Inzenieru 101, Ventspils 3601, Latvia

Received: 11 December 2019
Accepted: 12 February 2020

Abstract

Aims. The Seeds Of Life In Space IRAM/NOEMA large program aims at studying a set of crucial complex organic molecules in a sample of sources with a well-known physical structure that covers the various phases of solar-type star formation. One representative object of the transition from the prestellar core to the protostar phases has been observed toward the very low luminosity object (VeLLO) L1521F. This type of source is important to study to link prestellar cores and Class 0 sources and also to constrain the chemical evolution during the process of star formation.

Methods. Two frequency windows (81.6–82.6 GHz and 96.65–97.65 GHz) were used to observe the emission from several complex organics toward the L1521F VeLLO. These setups cover transitions of ketene (H₂CCO), propyne (CH₃CCH), formamide (NH₂CHO), methoxy (CH₃O), methanol (CH₃OH), dimethyl ether (CH₃OCH₃), and methyl formate (HCOOCH₃).

Results. Only two transitions of methanol (A⁺, E₂) have been detected in the narrow window centered at 96.7 GHz (with an upper limit on E₁) in a very compact emission blob (~7′′ corresponding to ~1000 au) toward the northeast of the L1521F protostar. The CS 2–1 transition is also detected within the WideX bandwidth. Consistently with what has been found in prestellar cores, the methanol emission appears ~1000 au away from the dust peak. The location of the methanol blob coincides with one of the filaments that have previously been reported in the literature. The excitation temperature of the gas inferred from methanol is (10 ± 2) K, while the H₂ gas density (estimated from the detected CS 2–1 emission and previous CS 5–4 ALMA observations) is a factor >25 higher than the density in the surrounding environment (n(H₂) ≥ 10⁷ cm⁻³).

Conclusions. Based on its compactness, low excitation temperature, and high gas density, we suggest that the methanol emission detected with NOEMA is (i) either a cold and dense shock-induced blob that formed recently (≤ a few hundred years) by infalling gas or (ii) a cold and dense fragment that may just have been formed as a result of the intense gas dynamics within the L1521F VeLLO system.