Gas phase Elemental abundances in Molecular cloudS (GEMS) I : The prototypical dark cloud TMC 1

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Fuente , A , Navarro , D G , Caselli , P , Gerin , M , Kramer , C , Roueff , E , Alonso-Albi , T , Bachiller , R , Cazaux , S , Commercon , B , Friesen , R , Garcia-Burillo , S , Giuliano , B M , Goicoechea , J R , Gratier , P , Hacar , A , Jimenez-Serra , I , Kirk , J , Lattanzi , F A , Loison , J C , Malinen , J , Marcelino , N , Martin-Domenech , R , Munoz-Caro , G , Pineda , J , Tafalla , M , Tercero , B , Ward-Thompson , D , Trevino-Morales , S P , Riviere-Marichalar , P , Roncero , O , Vidal , T & Ballester , M Y 2019 , ' Gas phase Elemental abundances in Molecular cloudS (GEMS) I : The prototypical dark cloud TMC 1 ' , Astronomy & Astrophysics , vol. 624 , A105 . https://doi.org/10.1051/0004-6361/201834654

Title: Gas phase Elemental abundances in Molecular cloudS (GEMS) I : The prototypical dark cloud TMC 1
Author: Fuente, A.; Navarro, D. G.; Caselli, P.; Gerin, M.; Kramer, C.; Roueff, E.; Alonso-Albi, T.; Bachiller, R.; Cazaux, S.; Commercon, B.; Friesen, R.; Garcia-Burillo, S.; Giuliano, B. M.; Goicoechea, J. R.; Gratier, P.; Hacar, A.; Jimenez-Serra, Izaskun; Kirk, J.; Lattanzi, Fernando Alfredo; Loison, J. C.; Malinen, J.; Marcelino, N.; Martin-Domenech, R.; Munoz-Caro, G.; Pineda, J.; Tafalla, M.; Tercero, B.; Ward-Thompson, D.; Trevino-Morales, S. P.; Riviere-Marichalar, P.; Roncero, O.; Vidal, T.; Ballester, M. Y.
Contributor: University of Helsinki, Department of Physics
Date: 2019-04-19
Language: eng
Number of pages: 25
Belongs to series: Astronomy & Astrophysics
ISSN: 1432-0746
URI: http://hdl.handle.net/10138/303684
Abstract: 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.
Subject: astrochemistry
ISM: abundances
ISM: kinematics and dynamics
ISM: molecules
stars: formation
stars: low-mass
POTENTIAL-ENERGY SURFACE
ROTATIONAL-EXCITATION
COMPARATIVE CHEMISTRY
INTERSTELLAR GAS
DIFFUSE CLOUDS
STAR-FORMATION
CO DEPLETION
TAURUS
SULFUR
IONIZATION
115 Astronomy, Space science
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