Evolutionary view through the starless cores in Taurus

Astronomy and Astrophysics, vol. 653, pp. A15

Abstract

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.

Authors 14

1. D. Navarro-Almaida

   Spanish National Observatory

   Affiliation as printed

   Observatorio Astronómico Nacional (OAN), Alfonso XII, 3, 28014, Madrid, Spain

2. Asunción Fuente

   Spanish National Observatory

   Affiliation as printed

   Observatorio Astronómico Nacional (OAN), Alfonso XII, 3, 28014, Madrid, Spain

3. Liton Majumdar

   National Institute of Science Education and Research

   Affiliation as printed

   School of Earth and Planetary Sciences, National Institute of Science Education and Research, HBNI, Jatni 752050, Odisha, India

4. Valentine Wakelam

   Centre National de la Recherche Scientifique · Laboratoire d'Astrophysique de Bordeaux

   Affiliation as printed

   Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France

5. P. Caselli

   Max Planck Institute for Extraterrestrial Physics

   Affiliation as printed

   Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748, Garching, Germany

6. P. Riviére-Marichalar

   Spanish National Observatory

   Affiliation as printed

   Observatorio Astronómico Nacional (OAN), Alfonso XII, 3, 28014, Madrid, Spain

7. Sandra P. Treviño-Morales

   Chalmers University of Technology

   Affiliation as printed

   Chalmers University of Technology, Department of Space, Earth and Environment, 412 93 Gothenburg, Sweden

8. Stéphanie M. Cazaux Aachen

   Leiden University · Delft University of Technology

   Affiliation as printed

   Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands

   University of Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands

9. Izaskun Jiménez-Serra

   Centro de Astrobiología

   Affiliation as printed

   Centro de Astrobiología (CSIC-INTA), Ctra. de Ajalvir, km 4, Torrejón de Ardoz, 28850, Madrid, Spain

10. Carsten Kramer

    Institut de Radioastronomie Millimétrique

    Affiliation as printed

    Institut de Radio Astronomie Millimétrique (IRAM), 300 Rue de la Piscine, Domaine Universitaire, 38406 Saint Martin d’Hères, France

11. A. Chacón-Tanarro

    Spanish National Observatory

    Affiliation as printed

    Observatorio Astronómico Nacional (OAN), Alfonso XII, 3, 28014, Madrid, Spain

12. Jason M. Kirk

    University of Lancashire

    Affiliation as printed

    Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK

13. Derek Ward-Thompson

    University of Lancashire

    Affiliation as printed

    Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK

14. Mario Tafalla

    Spanish National Observatory

    Affiliation as printed

    Observatorio Astronómico Nacional (OAN), Alfonso XII, 3, 28014, Madrid, Spain