Gas phase Elemental abundances in Molecular cloudS (GEMS) I. The prototypical dark cloud TMC 1
Artikel i vetenskaplig tidskrift, 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: formation

ISM: molecules

stars: low-mass


ISM: kinematics and dynamics

ISM: abundances


A. Fuente

Observatorio Astronómico Nacional (OAN)

D. G. Navarro

Observatorio Astronómico Nacional (OAN)

P. Caselli


M. Gerin

Observatoire de Paris

C. Kramer

Institut de Radioastronomie Millimétrique (IRAM)

E. Roueff

Université de recherche Paris Sciences et Lettres

T. Alonso-Albi

Observatorio Astronómico Nacional (OAN)

R. Bachiller

Observatorio Astronómico Nacional (OAN)

S. Cazaux

Universiteit Leiden

TU Delft

B. Commercon

Université de Lyon

R. Friesen

National Radio Astronomy Observatory

S. Garcia-Burillo

Observatorio Astronómico Nacional (OAN)

B. M. Giuliano


J. R. Goicoechea

Consejo Superior de Investigaciones Científicas (CSIC)

P. Gratier

Université de Bordeaux

A. Hacar

Universiteit Leiden

I Jimenez-Serra

Centro de Astrobiología (INTA-CSIC)

J. Kirk

The University of Warwick

V Lattanzi


J. C. Loison

Université de Bordeaux

J. Malinen

Universität zu Köln

Helsingin Yliopisto

N. Marcelino

Consejo Superior de Investigaciones Científicas (CSIC)

R. Martin-Domenech

Harvard-Smithsonian Center for Astrophysics

G. Munoz-Caro

Centro de Astrobiología (INTA-CSIC)

J. Pineda


M. Tafalla

Observatorio Astronómico Nacional (OAN)

B. Tercero

Observatorio Astronómico Nacional (OAN)

D. Ward-Thompson

University of Central Lancashire

Sandra Treviño Morales

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

P. Riviere-Marichalar

Observatorio Astronómico Nacional (OAN)

O. Roncero

Consejo Superior de Investigaciones Científicas (CSIC)

T. Vidal

Université de 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

Europeiska kommissionen (EU), 2016-01-01 -- 2021-01-31.


Meteorologi och atmosfärforskning

Astronomi, astrofysik och kosmologi




Mer information

Senast uppdaterat