Gas phase Elemental abundances in Molecular cloudS (GEMS): IV. Observational results and statistical trends
Artikel i vetenskaplig tidskrift, 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

Författare

M. Rodríguez-Baras

Observatorio Astronómico Nacional (OAN)

A. Fuente

Observatorio Astronómico Nacional (OAN)

P. Riviere-Marichalar

Observatorio Astronómico Nacional (OAN)

D. Navarro-Almaida

Observatorio Astronómico Nacional (OAN)

P. Caselli

Max-Planck-Gesellschaft

M. Gerin

Observatoire de Paris

C. Kramer

Institut de Radioastronomie Millimétrique (IRAM)

Evelyne Roueff

Observatoire de Paris

V. Wakelam

Université de Bordeaux

G. Esplugues

Observatorio Astronómico Nacional (OAN)

S. G. Burillo

Observatorio Astronómico Nacional (OAN)

R. Le Gal

Harvard-Smithsonian Center for Astrophysics

S. Spezzano

Max-Planck-Gesellschaft

T. Alonso-Albi

Observatorio Astronómico Nacional (OAN)

R. Bachiller

Observatorio Astronómico Nacional (OAN)

S. Cazaux

Universiteit Leiden

TU Delft

B. Commerçon

Ecole Normale Superieure de Lyon

J.R. Goicoechea

CSIC - Instituto de Fisica Fundamental (IFF)

J. C. Loison

Université de Bordeaux

Sandra Treviño Morales

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

O. Roncero

CSIC - Instituto de Fisica Fundamental (IFF)

I. Jimenez-Serra

Centro de Astrobiologia (CAB)

J. C. Laas

Max-Planck-Gesellschaft

A. Hacar

Universität Wien

J. Kirk

University of Central Lancashire

V. Lattanzi

Max-Planck-Gesellschaft

R. Martín-Doménech

Harvard-Smithsonian Center for Astrophysics

G. Muñoz-Caro

Centro de Astrobiologia (CAB)

J. E. Pineda

Max-Planck-Gesellschaft

B. Tercero

Observatorio de Yebes (IGN)

Observatorio Astronómico Nacional (OAN)

D. Ward-Thompson

University of Central Lancashire

M. Tafalla

Observatorio Astronómico Nacional (OAN)

N. Marcelino

CSIC - Instituto de Fisica Fundamental (IFF)

J. Malinen

Universität zu Köln

Helsingin Yliopisto

R. Friesen

National Radio Astronomy Observatory

B. M. Giuliano

Max-Planck-Gesellschaft

Astronomy and Astrophysics

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

Vol. 648 A120

Ämneskategorier

Fysikalisk kemi

Astronomi, astrofysik och kosmologi

Ekologi

DOI

10.1051/0004-6361/202040112

Mer information

Senast uppdaterat

2021-05-20