An automated method for planetary nebula detection with SIGNALS: first applications to NGC 4214 and NGC 4449

TL;DR

This paper introduces an automated pipeline for planetary nebula detection using emission-line diagnostics, applied to two galaxies, achieving high accuracy and discovering new PNe, with implications for distance measurement and galaxy analysis.

Contribution

The novel pipeline automates planetary nebula detection with accuracy comparable to visual methods and is validated on two dwarf galaxies from the SIGNALS survey.

Findings

Identified 25 PNe in NGC 4214, including 6 new discoveries.

Identified 23 PNe in NGC 4449, including 13 new discoveries.

Calculated PN luminosity function distances consistent with previous estimates.

Abstract

Utilising the optical imaging Fourier transform spectrograph SITELLE, the Star-formation, Ionized Gas and Nebular Abundances Legacy Survey (SIGNALS) is designed to study the connection between star-forming regions and their environments. Targeting $31$ local star-forming galaxies, its data products also lend themselves to planetary nebula (PN) surveys. We present here a new pipeline to find PNe using automated emission-line diagnostics and morphology tests, that is able to distinguish PNe from contaminants with an accuracy similar to that of past visual methods. We also perform thorough completeness tests using mock PNe inserted into the data cubes with full spectra. We apply these tools to a pilot sample of two dwarf irregular galaxies from the SIGNALS survey, NGC 4214 and NGC 4449, with other galaxies to follow. For these two galaxies, we identify $25$ PNe (including $6$ new discoveries) and $23$ PNe (including $13$ new discoveries), respectively, and calculate PN luminosity function distances of $3.09^{+0.25}_{-0.46}$ and $3.91^{+0.33}_{-0.52}$ Mpc, respectively, the latter consistent with previous estimates. We also calculate the bolometric PN specific frequency of our galaxies ($\alpha_\mathrm{bol}$), as well as a newly defined $V$-band PN specific frequency ($\alpha_\mathrm{V}$) based solely on the galaxies' total luminosities in that band.