Detection of HF Toward PKS 1830-211, Search for Interstellar H2F+, and Laboratory Study of H2F+ and H2Cl+ Dissociative Recombination
Artikel i vetenskaplig tidskrift, 2016

We report extragalactic observations of two fluorine-bearing species, hydrogen fluoride (HF) and fluoronium (H2F+), in the z = 0.89 absorber in front of the lensed blazar PKS 1830-211 with the Atacama Large Millimeter/submillimeter Array. HF was detected toward both southwest and northeast images of the blazar, with column densities >3.4 × 1014 cm-2 and 0.18 × 1014 cm-2, respectively. H2F+ was not detected, down to an upper limit (3?) of 8.8 × 1011 cm-2 and an abundance ratio of [H2F+]/[HF] 1/386. We also searched for H2F+ toward the Galactic sources NGC 6334 I and W51C, and toward Galactic center clouds with the Herschel HIFI spectrometer.6 The upper limit on the column density was derived to be 2.5 × 1011 cm-2 in NGC 6334 I, which is 1/68 of that for H2Cl+. In constrast, the ortho transition of H2Cl+ is detected toward PKS 1830-211. To understand the small abundance of interstellar H2F+, we carried out laboratory experiments to determine the rate constants for the ion-electron recombination reaction by infrared time-resolved spectroscopy. The constants determined are ke(209 K) = (1.1 ± 0.3) ×10-7 cm3 s-1 and (0.46 ± 0.05) ×10-7 cm3 s-1 for H2F+ and H2Cl+, respectively. The difference in the dissociative recombination rates between H2F+ and H2Cl+ by a factor ?2 and the cosmic abundance ratio [F]/[Cl] ? 1/6 are not enough to explain the much smaller abundance of H2F+. The difference in the formation mechanism of H2F+ and H2Cl+ in interstellar space would be a major factor in the small abundance of H2F+.

methods: laboratory: molecular

NGC 6334 I)

ISM: individual objects (W31C

galaxies: individual (PKS 1830-211)

ISM: molecules

Författare

K. Kawaguchi

Okayama University

Sebastien Muller

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

John H Black

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

T. Amano

University of Waterloo

F. Matsushima

University of Toyama

R. Fujimori

Nagoya University

Y. Okabayahsi

Okayama University

H. Nagahiro

Okayama University

Y. Miyamoto

Okayama University

J. Tang

Okayama University

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 822 Art. no. 115- 115

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

10.3847/0004-637X/822/2/115