SDSS-IV MaNGA: Galaxy Pair Fraction and Correlated Active Galactic Nuclei

TL;DR

This study analyzes galaxy pairs using MaNGA data, revealing that galaxy interactions significantly increase the occurrence of binary AGNs, with implications for understanding galaxy evolution and AGN activity.

Contribution

It provides the first detailed analysis of galaxy pair fractions and correlated AGN activity using integral-field spectroscopy from MaNGA, highlighting the excess of binary AGNs in close pairs.

Findings

Approximately 3% of M* galaxies are in close pairs.

Binary AGNs are found in about 13% of galaxy pairs, with a strong increase at smaller separations.

A fivefold excess of binary AGNs over random pairing is observed.

Abstract

We have identified 105 galaxy pairs at z ~ 0.04 with the MaNGA integral-field spectroscopic data. The pairs have projected separations between 1 kpc and 30 kpc, and are selected to have radial velocity offsets less than 600 km/s and stellar mass ratio between 0.1 and 1. The pair fraction increases with both the physical size of the integral-field unit and the stellar mass, consistent with theoretical expectations. We provide the best-fit analytical function of the pair fraction and find that ~3% of M* galaxies are in close pairs. For both isolated galaxies and paired galaxies, active galactic nuclei (AGN) are selected using emission-line ratios and H_alpha equivalent widths measured inside apertures at a fixed physical size. We find AGNs in ~24% of the paired galaxies and binary AGNs in ~13% of the pairs. To account for the selection biases in both the pair sample and the MaNGA sample, we compare the AGN comoving volume densities with those expected from the mass- and redshift-dependent AGN fractions. We find a strong (~5x) excess of binary AGNs over random pairing and a mild (~20%) deficit of single AGNs. The binary AGN excess increases from ~2x to ~6x as the projected separation decreases from 10-30 kpc to 1-10 kpc. Our results indicate that pairing of galaxies preserves the AGN duty cycle in individual galaxies but increases the population of binary AGNs through correlated activities. We suggest tidally-induced galactic-scale shocks and AGN cross-ionization as two plausible channels to produce low-luminosity narrow-line-selected binary AGNs.