H₂S observations in young stellar disks in Taurus

¹ Observatorio Astronómico Nacional (OAN, IGN), Calle Alfonso XII, 3. 28014 Madrid, Spain
e-mail: p.riviere@oan.es
² Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
³ IRAP, Université de Toulouse, CNRS, UPS, CNES, 31400 Toulouse, France
⁴ Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands
⁵ School of Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, UK
⁶ Centre for Exoplanet Science, University of St Andrews. North Haugh, St Andrews, KY16 9SS, UK
⁷ Leiden Observatory, Leiden University, PO Box 9513, NL 2300 RA Leiden, The Netherlands
⁸ European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile
⁹ Centro de Astrobiología (CSIC-INTA), Departamento de Astrofísica, ESA-ESAC Campus, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain

Received: 1 February 2021
Accepted: 26 May 2021

Abstract

Context. Studying gas chemistry in protoplanetary disks is key to understanding the process of planet formation. Sulfur chemistry in particular is poorly understood in interstellar environments, and the location of the main reservoirs remains unknown. Protoplanetary disks in Taurus are ideal targets for studying the evolution of the composition of planet forming systems.

Aims. We aim to elucidate the chemical origin of sulfur-bearing molecular emission in protoplanetary disks, with a special focus on H₂S emission, and to identify candidate species that could become the main molecular sulfur reservoirs in protoplanetary systems.

Methods. We used IRAM 30 m observations of nine gas-rich young stellar objects (YSOs) in Taurus to perform a survey of sulfur-bearing and oxygen-bearing molecular species. In this paper we present our results for the CS 3–2 (ν₀ = 146.969 GHz), H₂CO 2_1,1−1_1,0 (ν₀ = 150.498 GHz), and H₂S 1_1,0−1_0,1 (ν₀ = 168.763 GHz) emission lines.

Results. We detected H₂S emission in four sources out of the nine observed, significantly increasing the number of detections toward YSOs. We also detected H₂CO and CS in six out of the nine. We identify a tentative correlation between H₂S 1_1,0−1_0,1 and H₂CO 2_1,1−1_1,0 as well as a tentative correlation between H₂S 1_1,0−1_0,1 and H₂O 8₁₈−7₀₇. By assuming local thermodynamical equilibrium, we computed column densities for the sources in the sample, with N(o-H₂S) values ranging between 2.6 × 10¹² cm⁻² and 1.5 × 10¹³ cm⁻².