The excitation mechanisms and evolutionary stages of UWISH2 planetary nebula candidates

Jones, A. M. and Gledhill, T.M. and Froebrich, Dirk and Smith, M.D. (2018) The excitation mechanisms and evolutionary stages of UWISH2 planetary nebula candidates. Monthly Notices of the Royal Astronomical Society, 480 . pp. 1563-1579. ISSN 0035-8711. (doi:https://doi.org/10.1093/mnras/sty1931) (Full text available)

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Abstract

We present medium-resolution K-band long-slit spectroscopy of 29 true, likely, possible, and candidate Galactic Plane planetary nebulae (PNe) from the UWISH2 survey, many of which have only been recently discovered. These objects are bright in molecular hydrogen (H2) emission, and many have bipolar morphologies. Through the detection of the Brγ emission line, which traces ionized hydrogen, we find that the majority of the candidate PNe are indeed likely to be PNe, while 2 of the targets are more likely young stellar objects (YSOs) or pre-planetary nebulae (pPNe). We detect Brγ in 13 objects which have no detection in IPHAS or SHS Hα surveys. This implies that they are potential members of the little-known optically obscured PN population, hidden from wide-field optical surveys. We use the spatial extent of the H2 1-0 S(1) and Brγ lines to estimate the evolutionary stage of our targets, and find that W-BPNe (bipolar PNe with pinched waist morphologies) are likely to be younger objects, while R-BPNe (bipolar PNe with large ring structures) are more evolved. We use line ratios to trace the excitation mechanism of the H2, and find the 1-0 S(1) / 2-1 S(1) and 1-0 S(1) / Brγ ratios are higher for R-BPNe, implying the H2 is thermally excited. However, in W-BPNe, these ratios are lower, and so UV-fluorescence may be contributing to the excitation of H2.

Item Type: Article
Uncontrolled keywords: ISM: lines and bands, planetary nebulae: general, infrared: ISM
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Faculties > Sciences > School of Physical Sciences
Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Dirk Froebrich
Date Deposited: 08 Aug 2018 10:51 UTC
Last Modified: 14 Aug 2018 09:22 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/68512 (The current URI for this page, for reference purposes)
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