Star Formation of Merging Disk Galaxies with AGN Feedback Effects

TL;DR

This study uses numerical simulations to analyze how AGN feedback influences star formation during galaxy mergers, revealing that AGNs suppress star formation more in major mergers and that galaxy structure impacts this effect.

Contribution

It provides a comprehensive simulation-based analysis of AGN feedback effects across various merger scenarios, including different mass ratios and galaxy morphologies, highlighting the conditions under which AGNs significantly suppress star formation.

Findings

AGN suppresses star formation more in major mergers.

The effect of AGN feedback varies with galaxy morphology.

Discrepancy with recent observational results is discussed.

Abstract

Using numerical hydrodynamics code, we perform various idealized galaxy merger simulations to study the star formation (SF) of two merging disk galaxies. Our simulations include gas accretion onto supermassive black holes and active galactic nucleus (AGN) feedback. By comparing AGN simulations with those without AGNs, we attempt to understand when the AGN feedback effect is significant. With ~70 simulations, we investigated the SF with the AGN effect in mergers with variety of mass ratios, inclinations, orbits, galaxy structures and morphologies. Using these merger simulations with AGN feedback, we measure merger-driven SF using the burst efficiency parameter introduced by Cox et al. We confirm the previous studies that, in galaxy mergers, AGN suppresses SF more efficiently than in isolated galaxies. However, we additionally find that the effect of AGNs on SF is larger in major mergers than in minor mergers. In minor merger simulations with different primary bulge-to-total ratios, the effect of bulge fraction on the merger-driven SF decreases due to AGN feedback. We create models of Sa, Sb and Sc type galaxies and compare their SF properties while undergoing mergers. With the current AGN prescriptions, the difference in merger-driven SF is not as pronounced as that in the recent observational study of Kaviraj. We discuss the implications of this discrepancy.