OH+ and H2O+ absorption toward PKS 1830-211
Journal article, 2016

We report the detection of OH+ and H2O+ in the z = 0.89 absorber toward the lensed quasar PKS 1830-211. The abundance ratio of OH+ and H2O+ is used to quantify the molecular hydrogen fraction (fH2) and the cosmic-ray ionization rate of atomic hydrogen (ζH) along two lines of sight, located at 2 kpc and 4 kpc to either side of the absorber's center. The molecular fraction decreases outward, from 0.04 to 0.02, comparable to values measured in the Milky Way at similar galactocentric radii. For ζH , we find values of 2 × 10-14 s-1 and 3 × 10-15 s-1, respectively, which are slightly higher than in the Milky Way at comparable galactocentric radii, possibly due to a higher average star formation activity in the z = 0.89 absorber. The ALMA observations of OH+, H2O+, and other hydrides toward PKS 1830-211reveal the multi-phase composition of the absorbing gas. Taking the column density ratios along the southwest and northeast lines of sight as a proxy of molecular fraction, we classify the species ArH+, OH+, H2Cl+, H2O+, CH, and HF as tracing gases increasingly more molecular. Incidentally, our data allow us to improve the accuracy of H2O+ rest frequencies and thus refine the spectroscopic parameters.

quasar absorption lines


interstellar molecules

galaxies: abundances


Sebastien Muller

Chalmers, Earth and Space Sciences, Onsala Space Observatory

H. S. P. Müller

University of Cologne

John H Black

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

A. Beelen

Institut d'Astrophysique Spatiale

F. Combes

Centre national de la recherche scientifique (CNRS)

S.J. Curran

Victoria University of Wellington

M. Gerin

Ecole Normale Superieure (ENS)

M. Guélin

Ecole Normale Superieure (ENS)

Institut de Radioastronomie Millimétrique (IRAM)

C. Henkel

Max Planck Society

King Abdulaziz University

S. Martín

European Southern Observatory Santiago

Susanne Aalto

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

E. Falgarone

Ecole Normale Superieure (ENS)

K. M. Menten

Max Planck Society

P. Schilke

University of Cologne

Tommy Wiklind

Catholic University of America

M. A. Zwaan

European Southern Observatory (ESO)

Astronomy and Astrophysics

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

Vol. 595 A128(1-10) A128

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences


Onsala Space Observatory



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9/7/2018 1