Hydride spectroscopy of the diffuse interstellar medium: new clues on the gas fraction in molecular form and cosmic ray ionization rate in relation to H-3(+)

M. Gerin; F. Levrier; E. Falgarone; B. Godard; P. Hennebelle; F. Le Petit; M. de Luca; D. A. Neufeld; P. Sonnentrucker; P. F. Goldsmith; N. Flagey; D. C. Lis; Carina Persson; John H Black; J. R. Goicoechea; K. M. Menten

doi:10.1098/rsta.2012.0023

Hydride spectroscopy of the diffuse interstellar medium: new clues on the gas fraction in molecular form and cosmic ray ionization rate in relation to H-3(+)
Journal article, 2012

The Herschel-guaranteed time key programme PRobing InterStellar Molecules with Absorption line Studies (PRISMAS)(1) is providing a survey of the interstellar hydrides containing the elements C, O, N, F and Cl. As the building blocks of interstellar molecules, hydrides provide key information on their formation pathways. They can also be used as tracers of important physical and chemical properties of the interstellar gas that are difficult to measure otherwise. This paper presents an analysis of two sight-lines investigated by the PRISMAS project, towards the star-forming regions W49N and W51. By combining the information extracted from the detected spectral lines, we present an analysis of the physical properties of the diffuse interstellar gas, including the electron abundance, the fraction of gas in molecular form, and constraints on the cosmic ray ionization rate and the gas density.

nitrogen

W49N

diffuse interstellar medium

clouds

chloronium

g10.6-0.4 w31c

herschel/hifi observations

w49n

absorption-lines

regions

meudon pdr code

hydrides

sight-line

W51