Gas phase Elemental abundances in Molecular cloudS (GEMS): II. On the quest for the sulphur reservoir in molecular clouds: the H2S case
Artikel i vetenskaplig tidskrift, 2020

Context. Sulphur is one of the most abundant elements in the Universe. Surprisingly, sulphuretted molecules are not as abundant as expected in the interstellar medium and the identity of the main sulphur reservoir is still an open question.
Aims. Our goal is to investigate the H2S chemistry in dark clouds, as this stable molecule is a potential sulphur reservoir.
Methods. Using millimeter observations of CS, SO, H2S, and their isotopologues, we determine the physical conditions and H2S abundances along the cores TMC 1-C, TMC 1-CP, and Barnard 1b. The gas-grain model NAUTILUS is used to model the sulphur chemistry and explore the impact of photo-desorption and chemical desorption on the H2S abundance.
Results. Our modeling shows that chemical desorption is the main source of gas-phase H2S in dark cores. The measured H2S abundance can only be fitted if we assume that the chemical desorption rate decreases by more than a factor of 10 when n(H) > 2 x 10(4). This change in the desorption rate is consistent with the formation of thick H2O and CO ice mantles on grain surfaces. The observed SO and H2S abundances are in good agreement with our predictions adopting an undepleted value of the sulphur abundance. However, the CS abundance is overestimated by a factor of 5-10. Along the three cores, atomic S is predicted to be the main sulphur reservoir.
Conclusions. The gaseous H2S abundance is well reproduced, assuming undepleted sulphur abundance and chemical desorption as the main source of H2S. The behavior of the observed H2S abundance suggests a changing desorption efficiency, which would probe the snowline in these cold cores. Our model, however, highly overestimates the observed gas-phase CS abundance. Given the uncertainty in the sulphur chemistry, we can only conclude that our data are consistent with a cosmic elemental S abundance with an uncertainty of a factor of 10.

ISM: molecules

stars: low-mass

ISM: kinematics and dynamics

stars: formation

ISM: abundances

astrochemistry

Författare

D. Navarro-Almaida

Observatorio Astronómico Nacional (OAN)

R. Le Gal

Harvard-Smithsonian Center for Astrophysics

A. Fuente

Observatorio Astronómico Nacional (OAN)

P. Riviere-Marichalar

Observatorio Astronómico Nacional (OAN)

V Wakelam

Université de Bordeaux

S. Cazaux

Universiteit Leiden

TU Delft

P. Caselli

Max-Planck-Gesellschaft

J. C. Laas

Max-Planck-Gesellschaft

T. Alonso-Albi

Observatorio Astronómico Nacional (OAN)

J. C. Loison

Université de Bordeaux

M. Gerin

Université PSL

C. Kramer

Institut de Radioastronomie Millimétrique (IRAM)

E. Roueff

Sorbonne Université

R. Bachillerl

Observatorio Astronómico Nacional (OAN)

B. Commercon

Université de Lyon

R. Friesen

National Radio Astronomy Observatory

S. Garcia-Burillo

Observatorio Astronómico Nacional (OAN)

J. R. Goicoechea

Consejo Superior de Investigaciones Científicas (CSIC)

B. M. Giuliano

Max-Planck-Gesellschaft

I Jimenez-Serram

Consejo Superior de Investigaciones Científicas (CSIC)

J. M. Kirk

University of Central Lancashire

V Lattanzi

Max-Planck-Gesellschaft

J. Malinen

Helsingin Yliopisto

Universität zu Köln

N. Marcelino

Consejo Superior de Investigaciones Científicas (CSIC)

R. Martin-Domenech

Harvard-Smithsonian Center for Astrophysics

G. M. Munoz Caro

Consejo Superior de Investigaciones Científicas (CSIC)

J. Pineda

Max-Planck-Gesellschaft

B. Tercero

Observatorio Astronómico Nacional (OAN)

Sandra Treviño Morales

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Extragalaktisk astrofysik

O. Roncero

Consejo Superior de Investigaciones Científicas (CSIC)

A. Hacar

Universiteit Leiden

M. Tafalla

Observatorio Astronómico Nacional (OAN)

D. Ward-Thompson

University of Central Lancashire

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 637 A39

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/201937180

Mer information

Senast uppdaterat

2020-09-09