Mid-Infrared Variability in Nearby Galaxies from the MaNGA Sample

TL;DR

This study utilizes mid-infrared variability over thirteen years in a large galaxy sample to identify active galactic nuclei (AGN) and tidal disruption events, providing a new method for AGN detection in the local universe.

Contribution

It introduces a novel approach using mid-infrared variability from WISE data to detect AGN in nearby galaxies, validated with multiple AGN signatures and a publicly available catalog.

Findings

Approximately 75% of variable galaxies show additional AGN signatures.

Detected variability as small as 7% in W2 flux root-mean-square.

Identified seven galaxies with light-curves indicative of tidal disruption events.

Abstract

We use mid-infrared variability in galaxies to search for active galactic nuclei (AGN) in the local universe. We use a sample of 10,220 galaxies from the Mapping Nearby Galaxies at APO (MaNGA) survey, part of the Sloan Digital Sky Survey (SDSS-IV). For each galaxy, we examine its mid-infrared variability in the $W2$ $[4.6\mu m]$ band over thirteen years using data from the Wide Infrared Survey Explorer (WISE) All-Sky and Near Earth Objects WISE (NEOWISE) missions. We demonstrate that we can detect variability signatures as small as about $7\%$ in the root-mean-square variation of $W2$ flux for the majority of cases. Using other AGN signatures of the variable galaxies, such as optical narrow lines, optical broad lines, and WISE $W1-W2$ colors, we show that $\sim 75\%$ of the variables show these additional AGN signatures, indicating that the bulk of these cases are likely to be AGN. We also identify seven galaxies that have light-curves characteristic of tidal disruption events. We present here a publicly available catalog of the light-curve variability in $W2$ of these galaxies.