Optical Spectroscopy of Active Galactic Nuclei in SA57

TL;DR

This study uses optical spectroscopy to identify low luminosity AGNs in SA57, revealing that many are missed by optical surveys but can be detected through variability and X-ray emission, enhancing understanding of AGN populations.

Contribution

It provides a spectroscopic analysis of AGN candidates selected by variability and X-ray emission, identifying low luminosity AGNs often missed by optical surveys.

Findings

9 objects show typical AGN spectra

8 out of 10 Narrow Emission Line Galaxies exhibit variability suggestive of LLAGNs

Optical variability is a key indicator for LLAGNs in extended galaxies

Abstract

The cosmological evolution of X-ray-selected and optically selected Active Galactic Nuclei (AGNs) show different behaviours interpreted in terms of two different populations. The difference is evident mainly for low luminosity AGNs (LLAGNs), many of which are lost by optical photometric surveys. We are conducting a spectroscopical study of a composite sample of AGN candidates selected in SA57 following different searching techniques, to identify low luminosity AGNs and break down the sample into different classes of objects. AGN candidates were obtained through optical variability and/or X-ray emission. Of special interest are the extended variable objects, which are expected to be galaxies hosting LLAGNs. Among the 26 classified objects a fair number (9) show typical AGN spectra. 10 objects show Narrow Emission Line Galaxy spectra, and in most of them (8/10) optical variability suggests the presence of LLAGNs.