DETECTION of HF TOWARD PKS 1830-211, SEARCH for INTERSTELLAR H2F+, and LABORATORY STUDY of H2F+ and H2Cl+ DISSOCIATIVE RECOMBINATION

K. Kawaguchi, S. Muller, J. H. Black, T. Amano, F. Matsushima, R. Fujimori, Y. Okabayahsi, H. Nagahiro, Yuki Miyamoto, Jian Tang

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7 Citations (Scopus)

Abstract

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 (3σ) 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+.

Original languageEnglish
Article number115
JournalAstrophysical Journal
Volume822
Issue number2
DOIs
Publication statusPublished - May 10 2016

Keywords

  • galaxies: individual (PKS 1830-211)
  • ISM: individual objects (W31C, NGC 6334 I)
  • ISM: molecules
  • methods: laboratory: molecular

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

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