O CAESAR: The Optical CAtalogue of Extragalactic SupernovA Remnants

TL;DR

O CAESAR is a large, homogeneous optical survey of extragalactic supernova remnants using SITELLE, providing a systematic method for identifying and confirming SNR candidates across multiple galaxies.

Contribution

This work introduces a new survey and automated identification method for extragalactic SNRs using SITELLE data, with a focus on consistent, multi-line spectroscopic analysis.

Findings

First results for NGC 3344 demonstrate the method's effectiveness.

Automated identification based on [S II]/Hα ratio is successful.

Spectroscopic analysis confirms shock-heated ionization in candidates.

Abstract

We present O CAESAR, the Optical CAtalogue of Extragalactic SupernovA Remnants. O CAESAR will provide the largest homogeneous optical survey of extragalactic SNR candidates taken by the same telescope, the same instrument, and under similar observational conditions. Our sample is volume-limited (D $\leq$ 10 Mpc) and includes mostly galaxies ($\sim$40) from the Large Program SIGNALS. The Observations are carried out using SITELLE, the imaging Fourier transform spectrograph of the Canada-France-Hawaii Telescope. Using three filters, we are able to measure the strong emission lines [O II]$\lambda$3727, H$\beta$, [O III]$\lambda\lambda$4959,5007, H$\alpha$, [N II]$\lambda\lambda$6548,6583, and [S II]$\lambda\lambda$6716,6731. Identification of the SNR candidates will be done automatically and will be based on four criteria for regions where the emission lines flux ratio [S II]/H$\alpha$ $\ge$ 0.4. To confirm the shock-heated nature of the ionization mechanism in the candidates derived from our sample, we adopted a self-consistent spectroscopic analysis using the whole set of emission lines available with our SITELLE data and considering Sabbadin plots and BPT diagrams. We here present our method and first results for the spiral galaxy NGC 3344.