Coevolution of Dwarf Galaxies and Their Circumgalactic Medium Across Cosmic Time

TL;DR

This study uses high-resolution hydrodynamical simulations to explore the coevolution of dwarf galaxies and their circumgalactic medium across cosmic time, revealing the importance of CGM accretion and black hole growth in early universe galaxy evolution.

Contribution

It introduces a novel simulation approach combining realistic initial conditions from IllustrisTNG with increased resolution to study dwarf galaxy and CGM coevolution.

Findings

CGM evolution is sensitive to redshift.

CGM accretion supplies significant star-forming gas.

Black holes in high-z dwarfs grow rapidly with episodic accretion.

Abstract

Dwarf galaxies are thought of as the building blocks of large galaxies such as our Milky Way. This paper presents new high-resolution hydrodynamical simulations of dwarf galaxies and their intergalactic medium with the \texttt{GIZMO} code. Our simulations consider the key physical processes of galaxy evolution, such as gas cooling, chemistry, and stellar and black hole feedback. Unlike the previous work, the initial conditions of our simulations taking the dwarf galaxies of $2-5 \times 10^{10} \, M_\odot$ from the realistic cosmology simulations, \texttt{IllustrisTNG}. We further increase the original resolution of \texttt{IllustrisTNG} by a factor of $\sim 100$ via a particle splitting scheme. Our results show that the evolution of complex multiphase CGM and its metal content is sensitive to the redshift of dwarf galaxies. The accretion of CGM into dwarf galaxies plays a key role in providing $20 \% - 50 \%$ of the star-forming gas and replenishing $40 \% - 70 \%$ of the total mass in the galactic disk. Furthermore, the accretion history of supermassive black holes in the centers of high-$z$ dwarf galaxies shows episodic patterns with high-accreting states close to $\sim 10 \%$ of the Eddington mass accretion rate, implying the rapid growth of supermassive black holes in the early universe, which may be revealed by the coming observations from the James Webb Space Telescope (JWST).