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arXiv · 1603.06667

Spitzer mid-infrared spectroscopic observations of planetary nebulae

Héctor Mata·Gerardo Ramos-Larios·Martin A. Guerrero·Alberto Nigoche-Netro·Jesús A. Toalá·Xuan Fang·Gabriel M. Rubio·Simon N. Kemp·Silvana G. Navarro·Luis J. Corral
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Abstract

We present Spitzer Space Telescope archival mid-infrared (mid-IR) spectroscopy of a sample of eleven planetary nebulae (PNe). The observations, acquired with the Spitzer Infrared Spectrograph (IRS), cover the spectral range 5.2-14.5 μm that includes the H2 0-0 S(2) to S(7) rotational emission lines. This wavelength coverage has allowed us to derive the Boltzmann distribution and calculate the H2 rotational excitation temperature (Tex). The derived excitation temperatures have consistent values ~900+/-70 K for different sources despite their different structural components. We also report the detection of mid-IR ionic lines of [Ar III], [S IV], and [Ne II] in most objects, and polycyclic aromatic hydrocarbon (PAH) features in a few cases. The decline of the [Ar III]/[Ne II] line ratio with the stellar effective temperature can be explained either by a true neon enrichment or by high density circumstellar regions of PNe that presumably descend from higher mass progenitor stars.

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Héctor Mata, Gerardo Ramos-Larios, Martin A. Guerrero, Alberto Nigoche-Netro, Jesús A. Toalá, Xuan Fang, Gabriel M. Rubio, Simon N. Kemp, Silvana G. Navarro, Luis J. Corral. 2016-03-22. Spitzer mid-infrared spectroscopic observations of planetary nebulae. https://doi.org/10.1093/mnras%2Fstw646

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