Sulphur-bearing molecule survey towards prestellar and starless cores in the Perseus molecular cloud
Year: 2026
Type: article
Abstract: Sulphur is drastically depleted from the gas phase in dense starless and prestellar cores, creating the long-standing `missing sulphur problem'. Observations of sulphur-bearing molecules are crucial to understanding sulphur chemistry, the relationship of cores with their environments, and the physical evolution of star-forming regions. We present an observational survey of four sulphur-bearing molecules, HCS + $, OCS, H$_ 2 CS, and SO, towards dense cores in the Perseus molecular cloud with the aim of studying their abundance dependence on core physical properties and environment. The HCS + $ 1--0, the OCS 3--2 and 4--3, the H_2CS 1_0,1--0_0,0, and the SO 3_2--2$_ 2 transitions were observed with the Yebes 40m telescope towards 15 starless and prestellar cores in the Perseus molecular cloud. The lines were fitted with Gaussian profiles and their column densities were calculated assuming the local thermodynamic equilibrium approach. Additionally, a comparison with observations of other sulphur-bearing species towards the same core samples presented in a previous study, CS, CCS, and CCCS, was performed. The HCS + $, OCS, H_2CS, and SO are detected towards 100%, 93%, 100%, and 73% of the source sample, respectively. The derived column densities are (2.2 - 17.0)times10^11 cm^-2 for HCS^+, (1.9 - 25.0)times10^12 cm^-2 for OCS, (1.0 - 15.0)times10^12 cm^-2 for H_2CS, and (0.3 - 17.0)times10^13 cm$^ -2 for SO. The molecular column densities found span an order of magnitude or even more in the entire core sample. The abundances of HCS + and SO strongly correlate, inversely and directly, respectively, with the volume density of the cores, reinforcing their early- and late-type molecule status. The correlations found amongst the molecular abundances point at a differentiation between the `carbon chemistry' and `oxygen chemistry' of sulphur-bearing molecules. CS has the strongest abundance correlations with other molecules, as expected from its core role in sulphur chemistry. Cores located in the path of protostellar outflows do not show consistently higher sulphur-bearing molecule abundances compared to the rest of the sample. The chemical age of the cores, as traced by SO/CS, correlates with their physical age, traced using the volume density of the cores, with the exception of Per752, which shows an outlier chemical fingerprint, possibly related to an enhanced cosmic ray ionisation rate in the area. Overall, these results provide a crucial observational baseline offering tighter constraints for chemical models of the sulphur chemistry in the earliest stages of star formation.
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Awards: G1152523013, G121809054, G1397962376, G1507096846, G1622782223, G1743472294, G2309174360, G2660406951, G3518538256, G3702198118, G3926388292, G4212894969, G4515945706, Graduate Research Fellowship Program (GRFP), G5404395142, G5635532810, G5934669618, G5950425101, An Undergraduate Group Research Project: Large Scale Mapping of the Structure and Kinematics of Filaments and Cores in Nearby Molecular Clouds, G7097722406, G7805626310, G8920660035, G897484643, G9000362223
OpenAlex ID: W7221777584