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.

stars: low-mass

ISM: abundances

stars: formation


ISM: kinematics and dynamics

ISM: molecules


A. Fuente

Spanish National Observatory (OAN)

D. G. Navarro

Spanish National Observatory (OAN)

P. Caselli

Max Planck Society

M. Gerin

Paris Observatory

C. Kramer

Instituto de Radioastronomía Milimétrica

E. Roueff

PSL Research University

T. Alonso-Albi

Spanish National Observatory (OAN)

R. Bachiller

Spanish National Observatory (OAN)

S. Cazaux

Delft University of Technology

Leiden University

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, Galactic Astrophysics

P. Riviere-Marichalar

Spanish National Observatory (OAN)

O. Roncero

Spanish National Research Council (CSIC)

T. Vidal

University of Bordeaux

M. Y. Ballester

Universidade Federal de Juiz de Fora

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 624 A105

PROMISE Origins of the Molecular Cloud Structure

European Commission (Horizon 2020), 2016-01-01 -- 2021-01-31.

Subject Categories

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology




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