The Astrid Simulation: Evolution of Black Holes and Galaxies to <i>z</i> = 0.5 and Different Evolution Pathways for Galaxy Quenching

Abstract

Abstract We present new results from the ASTRID simulation from z = 3 to z = 0.5, covering the epoch of cosmic noon. The galaxy stellar mass function, as well as the black hole mass and luminosity functions in ASTRID , exhibit good agreement with recent observational constraints. We study the M BH – M * scaling relation and its connections to active galactic nucleus (AGN) luminosity, galaxy color, and star formation rate, demonstrating that AGN feedback plays a crucial role in the quenching of massive galaxies ( M * &gt; 10 10.5 M ⊙ ). Although AGN feedback ultimately suppresses star formation through quenching, AGN-host galaxies can still exhibit statistically higher star formation rates than inactive ones, reflecting a positive correlation driven by their shared dependence on a common cold gas reservoir. The fraction of quiescent galaxies in ASTRID increases with both galaxy mass and redshift evolution, aligning well with observational trends. We find that different quenching mechanisms can leave distinct morphological imprints on quenched galaxies. Massive, compact quiescent galaxies typically experience shorter quenching timescales, have younger central regions, and host overmassive black holes. This is usually due to a compaction-like quenching mechanism that funnels gas into the galactic center, leading to starbursts and triggering AGN kinetic feedback. In contrast, quiescent galaxies with more diffuse morphologies generally experience “inside-out” quenching, which is characterized by older central regions compared to the outskirts. These galaxies typically experience longer quenching timescales due to quenching processes operating on a larger halo scale, which gradually deplete the galactic star-forming gas. Data of the ASTRID simulation down to z = 0.5 is available at https://astrid.psc.edu .

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