Halo-driven Origin and Suppression of Over-massive Black Holes and Little Red Dots

TL;DR

This paper proposes a halo-driven theoretical model explaining the formation and evolution of over-massive black holes and Little Red Dots, linking early rapid growth phases to later regulated coevolution with host galaxies.

Contribution

It introduces a novel halo-driven framework that accounts for the emergence of OBHs and LRDs during a transient phase before standard SMBH-galaxy coevolution.

Findings

OBHs and LRDs arise during a halo-driven transient phase.

Transition in halo thermodynamics suppresses black hole growth.

Model unifies formation and evolution of OBHs and LRDs with local coevolution.

Abstract

We present a theoretical model in which the recently detected over-massive black holes (OBHs), and possibly Little Red Dots (LRDs), arise during a halo-driven transient phase preceding the established coevolution of supermassive black holes (SMBHs) and their host galaxies. In this model, halo gravity drives an early phase of rapid black hole growth, leading to systems in high-redshift haloes that lie above the local scaling relations. As the halo evolves, a transition in halo thermodynamics leads to the onset of a hot, pressure-supported medium that suppresses accretion, reducing the black hole growth rate and driving the system toward the local black hole mass$-$stellar mass relation. LRDs may represent an observational manifestation of the rapid, halo-driven growth phase, while OBHs trace its direct mass signature. Our model thus provides a unified framework in which these systems form and evolve toward the regulated coevolution observed in the local Universe.