Gas phase Elemental abundances in Molecular cloudS (GEMS) I. The prototypical dark cloud TMC 1
Journal article, 2019
GEMS is an IRAM 30 m Large Program whose aim is determining the elemental depletions and the ionization fraction in a set of prototypical star-forming regions. This paper presents the first results from the prototypical dark cloud Taurus molecular cloud (TMC) 1. Extensive millimeter observations have been carried out with the IRAM 30 m telescope (3 and 2mm) and the 40 m Yebes telescope (1.3 cm and 7 mm) to determine the fractional abundances of CO, HCO+, HCN, CS, SO, HCS+, and N2H+ in three cuts which intersect the dense filament at the well-known positions TMC 1-CP, TMC 1-NH3, and TMC 1-C, covering a visual extinction range from A(v) similar to 3 to similar to 20 mag. Two phases with differentiated chemistry can be distinguished: (i) the translucent envelope with molecular hydrogen densities of 1-5 x 10(3) cm(-3); and (ii) the dense phase, located at A(v) > 10 mag, with molecular hydrogen densities >10(4) cm(-3). Observations and modeling show that the gas phase abundances of C and O progressively decrease along the C+/C/CO transition zone (A(v) similar to 3 mag) where C/H similar to 8 x 10(-5) and C/O similar to 0.8-1, until the beginning of the dense phase at A(v) similar to 10 mag. This is consistent with the grain temperatures being below the CO evaporation temperature in this region. In the case of sulfur, a strong depletion should occur before the translucent phase where we estimate an S/H similar to (0.4-2.2) x 10(-6), an abundance similar to 7-40 times lower than the solar value. A second strong depletion must be present during the formation of the thick icy mantles to achieve the values of S/H measured in the dense cold cores (S/H similar to 8 x 10(-8)). Based on our chemical modeling, we constrain the value of zeta(H2) to similar to(0.5-1.8) x 10(-16) s(-1) in the translucent cloud.
ISM: abundances
ISM: kinematics and dynamics
stars: formation
ISM: molecules
astrochemistry
stars: low-mass
Author
A. Fuente
Spanish National Observatory (OAN)
D. G. Navarro
Spanish National Observatory (OAN)
P. Caselli
Max Planck Society
M. Gerin
Paris Observatory
C. Kramer
Institut de Radioastronomie Millimétrique (IRAM)
E. Roueff
Université Paris PSL
T. Alonso-Albi
Spanish National Observatory (OAN)
R. Bachiller
Spanish National Observatory (OAN)
S. Cazaux
Leiden University
Delft University of Technology
B. Commercon
Université de Lyon
R. Friesen
National Radio Astronomy Observatory
S. Garcia-Burillo
Spanish National Observatory (OAN)
B. M. Giuliano
Max Planck Society
J. R. Goicoechea
Spanish National Research Council (CSIC)
P. Gratier
University of Bordeaux
A. Hacar
Leiden University
I Jimenez-Serra
Spanish Astrobiology Center (INTA-CSIC)
J. Kirk
The University of Warwick
V Lattanzi
Max Planck Society
J. C. Loison
University of Bordeaux
J. Malinen
University of Helsinki
University of Cologne
N. Marcelino
Spanish National Research Council (CSIC)
R. Martin-Domenech
Harvard-Smithsonian Center for Astrophysics
G. Munoz-Caro
Spanish Astrobiology Center (INTA-CSIC)
J. Pineda
Max Planck Society
M. Tafalla
Spanish National Observatory (OAN)
B. Tercero
Spanish National Observatory (OAN)
D. Ward-Thompson
University of Central Lancashire
Sandra Treviño Morales
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
P. Riviere-Marichalar
Spanish National Observatory (OAN)
O. Roncero
Spanish National Research Council (CSIC)
T. Vidal
University of Bordeaux
M. Y. Ballester
Federal University of Juiz de Fora
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 624 A105PROMISE Origins of the Molecular Cloud Structure
European Commission (EC) (EC/H2020/639459), 2016-01-01 -- 2021-01-31.
Subject Categories
Meteorology and Atmospheric Sciences
Astronomy, Astrophysics and Cosmology
Geochemistry
DOI
10.1051/0004-6361/201834654