Gas phase Elemental abundances in Molecular cloudS (GEMS): IV. Observational results and statistical trends
Journal article, 2021

Gas phase Elemental abundances in Molecular CloudS (GEMS) is an IRAM 30 m Large Program designed to provide estimates of the S, C, N, and O depletions and gas ionization degree, X(e-), in a selected set of star-forming filaments of Taurus, Perseus, and Orion. Our immediate goal is to build up a complete and large database of molecular abundances that can serve as an observational basis for estimating X(e-) and the C, O, N, and S depletions through chemical modeling. We observed and derived the abundances of 14 species (13CO, C18O, HCO+, H13CO+, HC18O+, HCN, H13CN, HNC, HCS+, CS, SO, 34SO, H2S, and OCS) in 244 positions, covering the AV ~3 to ~100 mag, n(H2) ~ a few 103 to 106 cm-3, and Tk ~10 to ~30 K ranges in these clouds, and avoiding protostars, HII regions, and bipolar outflows. A statistical analysis is carried out in order to identify general trends between different species and with physical parameters. Relations between molecules reveal strong linear correlations which define three different families of species: (1) 13CO and C18O isotopologs; (2) H13CO+, HC18O+, H13 CN, and HNC; and (3) the S-bearing molecules. The abundances of the CO isotopologs increase with the gas kinetic temperature until TK ~ 15 K. For higher temperatures, the abundance remains constant with a scatter of a factor of ~3. The abundances of H13 CO+, HC18 O+, H13 CN, and HNC are well correlated with each other, and all of them decrease with molecular hydrogen density, following the law ∝ n(H2)-0.8  ±  0.2. The abundances of S-bearing species also decrease with molecular hydrogen density at a rate of (S-bearing/H)gas ∝ n(H2)-0.6  ±  0.1. The abundances of molecules belonging to groups 2 and 3 do not present any clear trend with gas temperature. At scales of molecular clouds, the C18O abundance is the quantity that better correlates with the cloud mass. We discuss the utility of the 13CO/C18O, HCO+/H13CO+, and H13 CO+/H13CN abundance ratios as chemical diagnostics of star formation in external galaxies.

Galaxies: ISM

ISM: clouds

Stars: formation

ISM: molecules

Astrochemistry

ISM: abundances

Author

M. Rodríguez-Baras

Spanish National Observatory (OAN)

A. Fuente

Spanish National Observatory (OAN)

P. Riviere-Marichalar

Spanish National Observatory (OAN)

D. Navarro-Almaida

Spanish National Observatory (OAN)

P. Caselli

Max Planck Society

M. Gerin

Paris Observatory

C. Kramer

Institut de Radioastronomie Millimétrique (IRAM)

Evelyne Roueff

Paris Observatory

V. Wakelam

University of Bordeaux

G. Esplugues

Spanish National Observatory (OAN)

S. G. Burillo

Spanish National Observatory (OAN)

R. Le Gal

Harvard-Smithsonian Center for Astrophysics

S. Spezzano

Max Planck Society

T. Alonso-Albi

Spanish National Observatory (OAN)

R. Bachiller

Spanish National Observatory (OAN)

S. Cazaux

Leiden University

Delft University of Technology

B. Commerçon

École Normale Supérieure de Lyon

J.R. Goicoechea

CSIC - Instituto de Fisica Fundamental (IFF)

J. C. Loison

University of Bordeaux

Sandra Treviño Morales

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

O. Roncero

CSIC - Instituto de Fisica Fundamental (IFF)

I. Jimenez-Serra

Centro de Astrobiologia (CAB)

J. C. Laas

Max Planck Society

A. Hacar

University of Vienna

J. Kirk

University of Central Lancashire

V. Lattanzi

Max Planck Society

R. Martín-Doménech

Harvard-Smithsonian Center for Astrophysics

G. Muñoz-Caro

Centro de Astrobiologia (CAB)

J. E. Pineda

Max Planck Society

B. Tercero

Yebes Observatory

Spanish National Observatory (OAN)

D. Ward-Thompson

University of Central Lancashire

M. Tafalla

Spanish National Observatory (OAN)

N. Marcelino

CSIC - Instituto de Fisica Fundamental (IFF)

J. Malinen

University of Cologne

University of Helsinki

R. Friesen

National Radio Astronomy Observatory

B. M. Giuliano

Max Planck Society

Astronomy and Astrophysics

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

Vol. 648 A120

Subject Categories

Physical Chemistry

Astronomy, Astrophysics and Cosmology

Ecology

DOI

10.1051/0004-6361/202040112

More information

Latest update

5/20/2021