The H$\alpha$ Halo Distribution of 10 Nearby Planetary Nebulae based on the SHASSA Imaging Data

TL;DR

This study uses SHASSA imaging data to identify extensive H-alpha halos around 10 nearby planetary nebulae, revealing their structure, possible formation mechanisms, and interaction with the interstellar medium.

Contribution

First systematic survey of extensive H-alpha halos around planetary nebulae using SHASSA data, highlighting their morphology and formation processes.

Findings

Most PNe in the sample have extensive outer halos.

Halos are mostly spherical and related to AGB mass loss.

Some halos show interaction with the interstellar medium.

Abstract

Here we present initial results of our search for extensive halos around the planetary nebulae (PNe) in our Galaxy based on imaging data from the Southern H-Alpha Sky Survey Atlas (SHASSA). A threshold surface brightness in H$\alpha$ emission was used to help identify the spatially extended features of the PNe. We investigated a sample that included 10 PNe, the large majority of which were found to be surrounded by extensive outer halos. The formation of these halos might be closely related to the AGB phase mass loss and/or the interaction of the stellar outflows with the interstellar medium. Most of these outer halos are nearly spherical. Close investigation of some specific objects, such as He 2-111 and NGC 3242, indicate a kinematic age on the order of 10$^{5}$ yrs. The mass loss history can be traced back to the late AGB phase of the evolution of the progenitors. Two objects form the sample (He 2-111, NGC 3242), were found to have outer halos with fragmented arcs that are apparently the result of their interaction with the interstellar medium.