Compact planetary nebulae: Improved IR diagnostic criteria based on classification tree modelling

Abstract

Planetary nebulae (PNe) are strong H$\alpha$ line-emitters and a lot of new PNe discoveries have been made by the SuperCOSMOS AAO/UKST H$\alpha$ Survey (SHS) and the Isaac Newton Telescope Photometric H$\alpha$ Survey (IPHAS). However, the list of auto-generated H$\alpha$-excess candidates from these surveys as well as any photometric survey, prior to spectroscopic follow-up to confirm their nature, contains all varieties of H$\alpha$-line emitters like young stellar objects (YSOs), H II regions, compact PNe and emission line stars of all kinds. The aim of this work is to find new infrared criteria that can better distinguish compact PNe from their mimics using a machine learning approach and the photometric data from the Two-Micron All-Sky Survey and Wide-field Infrared Survey Explorer. Three classification tree models have been developed with the following colour criteria: W1-W4$\ge$7.87 and J-H$<$1.10; H-W2$\ge$2.24 and J-H$<$0.50; and Ks-W3$\ge$6.42 and J-H$<$1.31 providing a list of candidates, characterized by a high probability to be genuine PNe. The contamination of this list of candidates from Ha mimics is low but not negligible. By applying these criteria to the IPHAS list of PN candidates and the entire IPHAS and VPHAS+ DR2 catalogues, we find 141 sources, from which 92 are known PNe, 39 are new very likely compact PNe (without an available classification or uncertain) and 10 are classified as H II regions, Wolf-Rayet stars, AeBe stars and YSOs. The occurrence of false positive identifications in this technique is between 10 and 15 per cent.

arXiv comment14 pages, 9 figures, Accepted for publication in MNRAS, comments are welcome

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• Determination of Planetary Nebulae angular diameters from radio continuum Spectral Energy Distribution modeling
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• Evolutionary Map of the Universe (EMU):Compact radio sources in the SCORPIO field towards the Galactic plane
• J-PLUS: Tools to identify compact planetary nebulae in the Javalambre and southern photometric local universe surveys
• Searching for nascent planetary nebulae: OHPNe candidates in the SPLASH survey
• A Survey for C II Emission-Line Stars in the Large Magellanic Cloud
• Mapping H$\alpha$-Excess Candidate Point Sources in the Southern Hemisphere Using S-PLUS Data
• Unveiling compact planetary nebulae: Broad-band survey analysis and LAMOST confirmation
• First Discovery and Confirmation of PN Candidates Found from AI and Deep Learning Techniques Applied to VPHAS+ Survey Data
• Detailed studies of IPHAS sources -- I. The disrupted late bipolar IPHASX J193718.6+202102
• Is the nitrogen-rich source PN K4-47 a true planetary nebula?
• Identifying Planetary Nebulae Candidates from IPHAS and VPHAS+ Surveys via YOLO Deep Learning Models