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

Ritik Sharma, Mahavir Sharma

First listed 2026-05-15 | Last updated 2026-05-15

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.

Short digest

This Letter proposes a halo-regulated black-hole growth sequence in which steady hydrodynamic accretion through a combined black-hole plus NFW halo potential drives an early, rapid-growth phase that can place high-redshift systems above the local black hole mass-stellar mass relation, in the regime occupied by recently reported over-massive black holes and plausibly some Little Red Dots. The key transition is then not feedback from the nucleus itself but halo thermodynamics: once the halo reaches a critical mass and develops virial-shock-heated, pressure-supported gas, accretion is suppressed and the tracks bend back toward the local scaling relations. The main payoff is a single spurt-and-quench framework that connects LRD-like accretion episodes, the direct mass signature of OBHs, and their later evolution into more regulated SMBH-galaxy coevolution.

Key figures to inspect

• Figure 1. Use this figure to introduce the core claim that halo-driven growth tracks can reproduce the redshift-space location of observed JWST over-massive black holes and LRD AGN candidates. The top panel shows the black-hole growth histories in different present-day halo families, while the bottom panel translates those same tracks into host stellar masses, making it the cleanest setup figure for the paper’s unified OBH plus LRD interpretation.
• Figure 2. This is the clearest pre-suppression diagnostic of why the model matters: it places the halo-driven tracks directly in the black hole mass-stellar mass plane against the local Reines and Volonteri relation and the JWST points. It shows how the rapid-growth phase naturally produces systems offset above the local relation, which is the paper’s starting point for interpreting OBHs and possible LRD counterparts.
• Figure 3. Recommend this as the transition figure because it adds the paper’s central regulatory ingredient, suppression by virial shocks once the halo crosses the critical mass scale. It demonstrates in redshift space how the earlier growth spurt is curtailed, linking the observed high-redshift population to a later slowdown rather than unbounded continued accretion.
• Figure 4. This is the strongest synthesis figure for the paper’s bottom-line conclusion because it shows how the suppressed tracks evolve back through the black hole mass-stellar mass plane toward the local relation. The inclusion of different critical halo masses for the massive-halo case also makes it the best figure for understanding the model sensitivity and the importance of halo-scale quenching in setting the final evolutionary path.
• Figure 5. Include this figure to capture the halo-centric physical interpretation that distinguishes the paper from purely galaxy- or AGN-feedback-based pictures. By plotting black hole mass against halo mass, with and without suppression, it makes explicit that the model’s driver and regulator are both properties of the host halo and connects the framework to broader SMBH-halo correlations.