Volume 653, September 2021
|Number of page(s)||25|
|Section||Interstellar and circumstellar matter|
|Published online||31 August 2021|
Evolutionary view through the starless cores in Taurus
Deuteration in TMC 1-C and TMC 1-CP
Observatorio Astronómico Nacional (OAN),
Alfonso XII, 3,
2 School of Earth and Planetary Sciences, National Institute of Science Education and Research, HBNI, Jatni 752050, Odisha, India
3 Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
4 Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748, Garching, Germany
5 Chalmers University of Technology, Department of Space, Earth and Environment, 412 93 Gothenburg, Sweden
6 Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands
7 University of Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
8 Centro de Astrobiología (CSIC-INTA), Ctra. de Ajalvir, km 4, Torrejón de Ardoz, 28850, Madrid, Spain
9 Institut de Radio Astronomie Millimétrique (IRAM), 300 Rue de la Piscine, Domaine Universitaire, 38406 Saint Martin d’Hères, France
10 Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
Accepted: 15 June 2021
Context. The chemical and physical evolution of starless and pre-stellar cores are of paramount importance to understanding the process of star formation. The Taurus Molecular Cloud cores TMC 1-C and TMC 1-CP share similar initial conditions and provide an excellent opportunity to understand the evolution of the pre-stellar core phase.
Aims. We investigated the evolutionary stage of starless cores based on observations towards the prototypical dark cores TMC 1-C and TMC 1-CP.
Methods. We mapped the prototypical dark cores TMC 1-C and TMC 1-CP in the CS 3 → 2, C34S 3 → 2, 13CS 2 → 1, DCN 1 → 0, DCN 2 → 1, DNC 1 → 0, DNC 2 → 1, DN13C 1 → 0, DN13C 2 → 1, N2H+ 1 → 0, and N2D+ 1 → 0 transitions. We performed a multi-transitional study of CS and its isotopologs, DCN, and DNC lines to characterize the physical and chemical properties of these cores. We studied their chemistry using the state-of-the-art gas-grain chemical code NAUTILUS and pseudo time-dependent models to determine their evolutionary stage.
Results. The central nH volume density, the N2H+ column density, and the abundances of deuterated species are higher in TMC 1-C than in TMC 1-CP, yielding a higher N2H+ deuterium fraction in TMC 1-C, thus indicating a later evolutionary stage for TMC 1-C. The chemical modeling with pseudo time-dependent models and their radiative transfer are in agreement with this statement, allowing us to estimate a collapse timescale of ~1 Myr for TMC 1-C. Models with a younger collapse scenario or a collapse slowed down by a magnetic support are found to more closely reproduce the observations towards TMC 1-CP.
Conclusions. Observational diagnostics seem to indicate that TMC 1-C is in a later evolutionary stage than TMC 1-CP, with a chemical age ~1 Myr. TMC 1-C shows signs of being an evolved core at the onset of star formation, while TMC 1-CP appears to be in an earlier evolutionary stage due to a more recent formation or, alternatively, a collapse slowed down by a magnetic support.
Key words: astrochemistry / ISM: kinematics and dynamics / ISM: abundances / ISM: molecules / stars: formation / stars: low-mass
© ESO 2021
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