Gas phase Elemental abundances in Molecular cloudS (GEMS) VI. A sulphur journey across star-forming regions: study of thioformaldehyde emission

Abstract

In the context of the IRAM 30m Large Program GEMS, we present a study of thioformaldehyde in several starless cores located in star-forming filaments of Taurus, Perseus, and Orion. We investigate the influence of the environmental conditions on the abundances of these molecules in the cores, and the effect of time evolution. We have modelled the observed lines of H2CS, HDCS, and D2CS using the radiative transfer code RADEX. We have also used the chemical code Nautilus to model the evolution of these species depending on the characteristics of the starless cores. We derive column densities and abundances for all the cores. We also derive deuterium fractionation ratios, Dfrac, to determine and compare the evolutionary stage between different parts of each star-forming region. Our results indicate that the north region of the B213 filament in Taurus is more evolved than the south, while the north-eastern part of Perseus presents an earlier evolutionary stage than the south-western zone. Model results also show that Dfrac decreases with the cosmic-ray ionisation rate, while it increases with density and with the degree of sulphur depletion. In particular, we only reproduce the observations when the initial sulphur abundance in the starless cores is at least one order of magnitude lower than the solar elemental sulphur abundance. The progressive increase in HDCS/H2CS and D2CS/H2CS with time makes these ratios powerful tools for deriving the chemical evolutionary stage of starless cores. However, they cannot be used to derive the temperature of these regions, since both ratios present a similar evolution at two different temperature ranges (7-11 K and 15-19 K). Regarding chemistry, (deuterated) thioformaldehyde is mainly formed through gas-phase reactions (double-replacement and neutral-neutral displacement reactions), while surface chemistry plays an important role as a destruction mechanism.

31 pages, 26 figures

References in corpus (32)

• Filamentary structure of star-forming complexes
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• CO Isotopologues in the Perseus Molecular Cloud Complex: the X-Factor and Regional Variations
• A Large Catalog of Accurate Distances to Local Molecular Clouds: The Gaia DR2 Edition
• A Compendium of Distances to Molecular Clouds in the Star Formation Handbook
• Modeling Sulfur Depletion in Interstellar Clouds
• The N2D+/N2H+ ratio as an evolutionary tracer of Class 0 protostars
• Detection of circumstellar CH2CHCN, CH2CN, CH3CCH and H2CS
• Sulphur-bearing molecules in diffuse molecular clouds: new results from SOFIA/GREAT and the IRAM 30 m telescope
• Sulphur-bearing species in the star forming region L1689N
• Efficient Production of S${}_8$ in Interstellar Ices: The effects of cosmic ray-driven radiation chemistry and non-diffusive bulk reactions
• Large Area Mapping at 850 Microns. V. Analysis of the Clump Distribution in the Orion A South Molecular Cloud
• Gas phase Elemental abundances in Molecular cloudS (GEMS). II. On the quest for the sulphur reservoir in molecular clouds: the $H_{2}S$ case
• Modelling the sulphur chemistry evolution in Orion KL
• A shallow though extensive H2 2.12 micron imaging survey of Taurus-Auriga-Perseus: I. NGC1333, L1455, L1448 and B1
• Photoprocessing of H2S on dust grains: building S chains in translucent clouds and comets
• Complex organic molecules in strongly UV-irradiated gas
• Chemical evolution in the early phases of massive star formation II: Deuteration
• The Distances to Molecular Clouds at High Galactic Latitudes based on GAIA DR2
• A 3D view of the Taurus star-forming region by Gaia and Herschel: multiple populations related to the filamentary molecular cloud
• Gas phase Elemental abundances in Molecular cloudS (GEMS). IV. Observational results and statistical trends
• The cosmic-ray ionisation rate in the pre-stellar core L1544
• Molecular Line Observations of a Carbon-Chain-Rich Core L492
• Deuteration around the ultracompact HII region Mon R2
• Catalog of dense cores in the Orion A giant molecular cloud
• The initial gas-phase sulfur abundance in the Orion Molecular Cloud from sulfur radio recombination lines
• Evolutionary view through the starless cores in Taurus: deuteration in TMC 1-C and TMC 1-CP
• Gas-phase Elemental abundances in Molecular cloudS (GEMS) III. Unlocking the CS chemistry: the CS+O reaction
• LOFAR observations of a jet-driven piston shock in the low solar corona
• Gas phase Elemental abundances in Molecular cloudS (GEMS) V. Methanol in Taurus
• Bayesian Estimation of the D(p,$\gamma$)${}^3$He Thermonuclear Reaction Rate
• The SVS13-A Class I chemical complexity as revealed by S-bearing species. SOLIS XIII

Cited by in corpus (12)

• Gas phase Elemental abundances in Molecular cloudS (GEMS) VII. Sulfur elemental abundance
• The GRETOBAPE gas-phase reaction network: the importance of being exothermic
• Linking the dust and chemical evolution: Taurus and Perseus -- New collisional rates for HCN, HNC, and their C, N, and H isotopologues
• SO2 and OCS toward high-mass protostars: A comparative study between ice and gas
• Formation of carbonyl sulfide (OCS) via SH radicals in interstellar CO-rich ice under dense cloud conditions
• Evolution of Chemistry in the envelope of Hot Corinos (ECHOS). I. Extremely young sulphur chemistry in the isolated Class 0 object B335
• First detection of HS2 in a cold dark cloud
• Gas phase Elemental abundances in Molecular cloudS (GEMS). IX. Deuterated compounds of H2S in starless cores
• Gas phase Elemental abundances in Molecular cloudS (GEMS) VIII. Unlocking the CS chemistry: the CH + S$\to$ CS + H and C${}_2$ + S$\to$ CS + C reactions
• Observational studies on S-bearing molecules in massive star forming regions
• Gas phase Elemental abundances in Molecular cloudS (GEMS). X. Observational effects of turbulence on the chemistry of molecular clouds
• Gas-phase Elemental abundances in Molecular cloudS (GEMS) XI. The evolution of HCN, HNC, and N2H+ isotopic ratios in starless cores