New Galactic Planetary Nebulae selected by radio and multi-wavelength characteristics

TL;DR

This study demonstrates that combining radio and multi-wavelength data effectively identifies new Galactic planetary nebulae, especially Type I PNe with dusty environments, confirmed through spectroscopic follow-up.

Contribution

The paper introduces a successful multi-wavelength selection method for discovering new Galactic PNe, particularly Type I, using radio data and optical/infrared diagnostics.

Findings

Confirmed 7 out of 8 spectroscopically observed candidates as PNe.

High success rate in identifying Type I PNe in dusty, high-extinction regions.

Multi-wavelength approach proves effective in detecting PNe missed by optical surveys.

Abstract

We have used the Cornish radio catalogue combined with the use of multi-wavelength data to identify 62 new Planetary Nebula (PN) candidates close to the Galactic mid-plane. Of this sample 11 have weak optical counterparts in deep narrow band H$\alpha$ imaging that allows their spectroscopic follow-up. We have observed eight of these candidates spectroscopically, leading to the confirmation of 7 out of 8 as PNe. All but one of our sample of newly detected PNe appear to be of Type I chemistry with very large [NII]/H$\alpha$ ratios. This indicates that our selection method heavily favours detection of this kind of PN. Cornish is a low Galactic latitude survey where young objects and Type I PNe (thought to derive from higher mass progenitors) are more plentiful, but where optical extinction is large. The very high success rate in correctly identifying PNe in this zone proves the efficacy of our radio and multiple multi-wavelength diagnostic tools used to successfully predict and then confirm their PN nature, at least in the cases where an optical counterpart is found and has been observed. The study reinforces the effective use of a combination of multi-wavelength and optical data in the identification of new Galactic PNe and especially those of Type I chemistries whose dusty environments often prevents their easy detection in the optical regime alone.