EUROPEAN SPACE AGENCY

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

DOI: 10.1051/0004-6361/201322940 Bibcode: 2014A&A...566A..79A

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

Netherlands, United States, Japan, Belgium, United Kingdom, Poland, Spain, Sweden, Germany

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.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

2014 • Astronomy and Astrophysics
Herschel 30
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