Confirmation of interstellar HOC+: Reevaluating the [HCO+]/[HOC+] abundance ratio

Lucy M Ziurys, A. J. Apponi

Research output: Contribution to journalArticle

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Abstract

The identification of interstellar HOC+ has been confirmed through new observations of this species at 3, 2, and 1.2 mm using the NRAO 12 m telescope. Toward Sgr B2 (OH), the J = 2 → 1 and J = 3 → 2 lines of this ion at 179 and 268 GHz were detected for the first time. In addition, the J = 1 → 0 line of HOC+ at 89 GHz was observed toward several new sources, including Orion-KL. In conjunction with past observations of the J = 1 → 0 transition toward Sgr B2 (OH), these data clearly establish the presence of this species in the interstellar medium. The column density toward Sgr B2 (OH) is estimated to be Ntot ∼ 3 × 1012 cm-2, which corresponds to a fractional abundance relative to H2 of f ∼ 10-12. Measurements of HCO+ were also carried out toward Sgr B2 (OH), resulting in an abundance ratio of [HCO+]/[HOC+] ∼ 140-360 at gas densities of n(H2) > 105 cm-3. This ratio contradicts past predictions of ion-molecule models by several orders of magnitude and suggests that the reaction HOC+ + H2 → HCO+ + H2 is not as fast as previously thought.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume455
Issue number1 PART 2
StatePublished - Dec 10 1995
Externally publishedYes

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ion
gas density
relative abundance
ions
telescopes
prediction
predictions
gas
molecules

Keywords

  • Galaxy: center
  • ISM: abundances
  • ISM: molecules
  • Line: identification

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Confirmation of interstellar HOC+ : Reevaluating the [HCO+]/[HOC+] abundance ratio. / Ziurys, Lucy M; Apponi, A. J.

In: Astrophysical Journal, Vol. 455, No. 1 PART 2, 10.12.1995.

Research output: Contribution to journalArticle

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N2 - The identification of interstellar HOC+ has been confirmed through new observations of this species at 3, 2, and 1.2 mm using the NRAO 12 m telescope. Toward Sgr B2 (OH), the J = 2 → 1 and J = 3 → 2 lines of this ion at 179 and 268 GHz were detected for the first time. In addition, the J = 1 → 0 line of HOC+ at 89 GHz was observed toward several new sources, including Orion-KL. In conjunction with past observations of the J = 1 → 0 transition toward Sgr B2 (OH), these data clearly establish the presence of this species in the interstellar medium. The column density toward Sgr B2 (OH) is estimated to be Ntot ∼ 3 × 1012 cm-2, which corresponds to a fractional abundance relative to H2 of f ∼ 10-12. Measurements of HCO+ were also carried out toward Sgr B2 (OH), resulting in an abundance ratio of [HCO+]/[HOC+] ∼ 140-360 at gas densities of n(H2) > 105 cm-3. This ratio contradicts past predictions of ion-molecule models by several orders of magnitude and suggests that the reaction HOC+ + H2 → HCO+ + H2 is not as fast as previously thought.

AB - The identification of interstellar HOC+ has been confirmed through new observations of this species at 3, 2, and 1.2 mm using the NRAO 12 m telescope. Toward Sgr B2 (OH), the J = 2 → 1 and J = 3 → 2 lines of this ion at 179 and 268 GHz were detected for the first time. In addition, the J = 1 → 0 line of HOC+ at 89 GHz was observed toward several new sources, including Orion-KL. In conjunction with past observations of the J = 1 → 0 transition toward Sgr B2 (OH), these data clearly establish the presence of this species in the interstellar medium. The column density toward Sgr B2 (OH) is estimated to be Ntot ∼ 3 × 1012 cm-2, which corresponds to a fractional abundance relative to H2 of f ∼ 10-12. Measurements of HCO+ were also carried out toward Sgr B2 (OH), resulting in an abundance ratio of [HCO+]/[HOC+] ∼ 140-360 at gas densities of n(H2) > 105 cm-3. This ratio contradicts past predictions of ion-molecule models by several orders of magnitude and suggests that the reaction HOC+ + H2 → HCO+ + H2 is not as fast as previously thought.

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