Herschel Planetary Nebula Survey (HerPlaNS): First detection of OH + in planetary nebulae

I. Aleman, T. Ueta, D. Ladjal, K. M. Exter, J. H. Kastner, R. Montez, A. G.G.M. Tielens, Y. H. Chu, H. Izumiura, I. McDonald, R. Sahai, N. Siódmiak, R. Szczerba, P. A.M. Van Hoof, E. Villaver, W. Vlemmings, M. Wittkowski, A. A. Zijlstra

Research output: Contribution to journalArticlepeer-review

Abstract

Aims. We report the first detections of OH+ emission in planetary nebulae (PNe). Methods. As part of an imaging and spectroscopy survey of 11 PNe in the far-IR using the PACS and SPIRE instruments aboard the Herschel Space Observatory, we performed a line survey in these PNe over the entire spectral range between 51μm and 672μm to look for new detections. Results. The rotational emission lines of OH+ at 152.99, 290.20, 308.48, and 329.77μm were detected in the spectra of three planetary nebulae: NGC 6445, NGC 6720, and NGC 6781. Excitation temperatures and column densities derived from these lines are in the range of 27-47 K and 2 × 1010-4 × 1011 cm-2, respectively. Conclusions. In PNe, the OH+ rotational line emission appears to be produced in the photodissociation region (PDR) in these objects. The emission of OH+ is observed only in PNe with hot central stars (Teff> 100 000 K), suggesting that high-energy photons may play a role in OH+ formation and its line excitation in these objects, as seems to be the case for ultraluminous galaxies.

Original languageEnglish (US)
Article numberA79
JournalAstronomy and Astrophysics
Volume566
DOIs
StatePublished - Jun 2014

Keywords

  • Astrochemistry
  • Circumstellar matter
  • Planetary nebulae: general
  • Planetary nebulae: individual: NGC 6445
  • Planetary nebulae: individual: NGC 6720
  • Planetary nebulae: individual: NGC 6781

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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