The AGN contribution to the UV-FIR luminosities of interacting galaxies and its role in identifying the Main Sequence

TL;DR

This study analyzes the impact of active galactic nuclei (AGNs) on the luminosities of interacting galaxies and their role in galaxy evolution, using multi-wavelength data and spectral energy distribution modeling of 189 nearby galaxies.

Contribution

It provides a comprehensive SED analysis of a large galaxy sample, revealing how AGN activity influences star formation and galaxy properties during interactions.

Findings

Luminous galaxies >10^10 M_sun deviate from the main sequence.

Infrared AGN luminosity correlates tightly with stellar mass.

Buried AGNs occupy a transitional locus between starbursts and pure AGNs.

Abstract

Emission from active galactic nuclei (AGNs) is known to play an important role in the evolution of many galaxies including luminous and ultraluminous systems (U/LIRGs), as well as merging systems. However, the extent, duration, and exact effects of its influence are still imperfectly understood. To assess the impact of AGNs on interacting systems, we present a Spectral Energy Distribution (SED) analysis of a sample of 189 nearby galaxies. We gather and systematically re-reduce archival broad-band imaging mosaics from the ultraviolet to the far-infrared using data from GALEX, SDSS, 2MASS, IRAS, WISE, Spitzer and Herschel. We use spectroscopy from Spitzer/IRS to obtain fluxes from fine-structure lines that trace star formation and AGN activity. Utilizing the SED modelling and fitting tool CIGALE, we derive the physical conditions of the ISM, both in star-forming regions and in nuclear regions dominated by the AGN in these galaxies. We investigate how the star formation rates (SFRs) and the fractional AGN contributions ($f_{\rm{AGN}}$) depend on stellar mass, galaxy type, and merger stage. We find that luminous galaxies more massive than about $10^{10} \rm{M}_{*}$ are likely to deviate significantly from the conventional galaxy main-sequence relation. Interestingly, infrared AGN luminosity and stellar mass in this set of objects are much tighter than SFR and stellar mass. We find that buried AGNs may occupy a locus between bright starbursts and pure AGNs in the $f_{\rm{AGN}}$-[Ne V]/[Ne II] plane. We identify a modest correlation between $f_{\rm{AGN}}$ and mergers in their later stages.