Enhanced Star Formation and Black Hole Accretion Rates in Galaxy Mergers in IllustrisTNG50

Abstract

Many theoretical and observational studies have suggested that galaxy mergers may trigger enhanced star formation or active galactic nucleus activity. We present an analysis of merging and nonmerging galaxies from 0.2 ≤ z ≤ 3 in the IllustrisTNG50 simulation. These galaxies encompass a range of masses (M⋆ > 108 M⊙) and mass ratios (≥1:10) and multiple merger stages. We examine the effect that galaxy mergers have on star formation and black hole accretion rates in the TNG50 universe. We additionally investigate how galaxy and black hole mass, merger stage, merger mass ratio, and redshift affect these quantities. Mergers in our sample show excess specific star formation rates (sSFR) at z ≤ 3 and enhanced specific black hole accretion rates (sBHAR) at z ≲ 2. The difference between sSFRs and sBHARs in the merging sample compared to the nonmerging sample increases as redshift decreases. Additionally, we show that these enhancements persist for at least ∼1 Gyr after the merger event. Investigating how mergers behave in the TNG50 simulation throughout cosmic time enables both a better appreciation of the importance of spatial resolution in cosmological simulations and a better basis to understand our high-z Universe with observations from JWST.

Publisher

IOP Publishing Ltd.

Publication Date

8-20-2025

Publication Title

The Astrophysical Journal

Department

Physics and Astronomy

Document Type

Article

DOI

https://doi.org/10.3847/1538-4357/ade791

Keywords

Active galactic nuclei, Digital sky survey, Epoch simulations flares, Atomic gas fractions, AGN host galaxies, Similar-to 0.6, Scaling relations, Major mergers, Molecular gas, X-ray

Language

English

Format

text

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