The signature of LLAGNs in the nearby universe

TL;DR

This paper identifies low luminosity active galactic nuclei (LLAGNs) in nearby galaxies using a diagnostic diagram based on emission line ratios, revealing their signature in the local universe.

Contribution

It introduces a diagnostic method to classify LLAGNs in galaxies lacking complete emission line data, expanding the tools for AGN identification.

Findings

LLAGNs are prevalent in the nearby universe.

The diagnostic diagram effectively identifies LLAGNs.

These galaxies show emission line ratios consistent with low luminosity AGNs.

Abstract

We have used the diagnostic diagram that compares the ratio of emission lines [NII]\lambda6584/H\alpha with the equivalent width of [NII]$\lambda$6584, as proposed by Coziol et al. (1998), to determine the source of ionization of SDSS NELGs that cannot be classified by standard diagnostic diagrams, because the emission line [OIII]$\lambda$5007, H\beta, or both, are missing. We find these galaxies to be consistent with low luminosity AGNs, suggesting that this characteristic is the signature of the LLAGNs in the nearby Universe.