A Spitzer Study of Interacting Luminous and Ultra-Luminous Infrared Galaxies

TL;DR

This study uses Spitzer observations to analyze the roles of starbursts and AGNs in 28 interacting luminous infrared galaxies, examining how these activities relate to galaxy luminosity, merger stage, and interaction effects.

Contribution

It provides new infrared diagnostic diagrams and insights into the relative importance of star formation and nuclear activity in interacting IR-luminous galaxies.

Findings

Higher luminosity correlates with increased AGN activity.

Merger stage influences the prevalence of starbursts and AGNs.

Infrared diagnostics reveal activity types more clearly than optical data.

Abstract

We conducted a Spitzer Space Telescope survey of 28 Luminous (11 < log(LIR/L_odot) < 12, LIRGs) and Ultra-Luminous Infrared Galaxies (log(LIR/L_odot) > 12, ULIRGs). Many of these galaxies are found in pairs or associations and are powered by either nuclear activity or starformation (Sanders & Mirabel 1996). Our main goal is to understand the relative importance of starbursts and AGNs in interacting systems. Is the frequency of AGN and starbursts in these interacting galaxies related to their luminosities? What is the importance of the merger stage and the frequency of AGNs? We present our conclusions and diagnostic diagrams based in the observed near infrared lines and compare to studies based solely in optical data.