Unusual Carbonaceous Dust Distribution in PN G095.2+00.7

TL;DR

This study examines the distribution and characteristics of polycyclic aromatic hydrocarbons in a young planetary nebula, revealing spatial variations in infrared features influenced by UV radiation, and proposes a dust evolution mechanism.

Contribution

It introduces a spatially resolved analysis of PAH features in a planetary nebula, highlighting the role of UV radiation and self-extinction in dust feature evolution.

Findings

Broad 12 μm emission is shell-like and spatially distributed.

11.3 μm PAH feature varies across the nebula, enhanced in the south.

UV radiation differences explain spectral variations without dust processing.

Abstract

We investigate the polycyclic aromatic hydrocarbon features in the young Galactic planetary nebula PN G095.2+00.7 based on mid-infrared observations. The near- to mid-infrared spectra obtained with the AKARI/IRC and the Spitzer/IRS show the PAH features as well as the broad emission feature at 12 {\mu}m usually seen in proto-planetary nebulae (pPNe). The spatially resolved spectra obtained with Subaru/COMICS suggest that the broad emission around 12 {\mu}m is distributed in a shell-like structure, but the unidentified infrared band at 11.3 {\mu}m is selectively enhanced at the southern part of the nebula. The variation can be explained by a difference in the amount of the UV radiation to excite PAHs, and does not necessarily require the chemical processing of dust grains and PAHs. It suggests that the UV self-extinction is important to understand the mid-infrared spectral features. We propose a mechanism which accounts for the evolutionary sequence of the mid-infrared dust features seen in a transition from pPNe to PNe.