MESA-QUEST: Tracing the formation of direct collapse black hole seeds via quasi-stars

TL;DR

The rapid appearance of supermassive black holes at $z \gtrsim 9$ demands heavy-seed formation via direct collapse. The authors develop MESA-QUEST, a MESA-based framework to model quasi-star evolution, incorporating flexible inner-boundary conditions (Bondi vs saturated-convection), BH accretion luminosity, and various wind mass-loss prescriptions, to assess heavy-seed viability. They find that saturated-convection boundaries can yield BH-to-total mass fractions up to about $\sim 0.55\,M_*$, enabling substantial seed growth, whereas Bondi boundaries produce smaller BHs; strong radiation-driven winds can drastically limit growth and potentially quench heavy-seed formation unless envelope accretion offsets losses. These results delineate the physical regimes under which quasi-stars can form heavy seeds capable of evolving into the earliest SMBHs, informing interpretations of JWST and Chandra observations and guiding future theoretical work on early SMBH seeding and growth, while highlighting the need for including rotation, magnetic fields, and GR-radiation hydrodynamics in subsequent studies.

Abstract

The origin of the first supermassive black holes (SMBHs) observed at redshifts $z\geq 9$ remains one of the most challenging open questions in astrophysics. Their rapid emergence suggests that massive ``heavy seeds'' must have formed early, possibly through the direct collapse of pristine gas clouds in the first galaxies. We present MESA-QUEST, a new framework built upon the Modules for Experiments in Stellar Astrophysics (MESA) code, designed to model the structure and evolution of quasi-stars -- massive, radiation-supported envelopes hosting accreting black holes at their cores -- believed to be the progenitors of direct-collapse black hole (DCBH) seeds. Our implementation introduces flexible boundary conditions representing both Bondi accretion and saturated-convection regimes, and explores the impact of several stellar wind and mass-loss prescriptions, including Reimers, Dutch, and super-Eddington radiation-driven winds. We find that quasi-stars can grow central black holes to $\geq 10^3\,M_{\odot}$ under favorable conditions, with saturated-convection models yielding BH-to-total mass ratios up to 0.55$M_*$ -- five times higher than Bondi-limited cases. However, strong radiation-driven winds can dramatically curtail growth, potentially quenching heavy-seed formation unless balanced by sustained envelope accretion. Our results delineate the physical limits under which quasi-stars can remain stable and produce heavy seeds capable of evolving into the earliest SMBHs detected by JWST and Chandra. Future extensions will incorporate rotation, magnetic fields, and GR-radiation hydrodynamics to refine accretion physics and constrain the viability of the quasi-star pathway for early SMBH formation.

Figures (3)

• Figure 1: The No Wind Scheme: Total radius (top, solid) and inner boundary radius (top, dashed) as well as the effective temperature and core density (bottom) as a function of black hole mass for both the Bondi (left) and saturated-convection (right) inner boundary conditions without any wind scheme implementation. We include four models with various values of $\alpha$: $\alpha=0.5$ (yellow), $\alpha=0.8$ (orange), $\alpha=1.0$ (red), and $\alpha=1.4$ (maroon).
• Figure 2: Core opacities for both Bondi (left) and saturated-convection (right) models. We include models with $\alpha=0.5$ (yellow), $\alpha=0.8$ (orange), $\alpha=1.0$ (red), and $\alpha=1.4$ (maroon).
• Figure 3: Dutch Wind Scheme:(See Fig. \ref{['fig:nowind']}) Total radius (top, solid) and inner boundary radius (top, dashed) as well as the effective temperature and core density (bottom) as a function of black hole mass for both the Bondi (left) and saturated-convection (right) inner boundary conditions now with the Dutch wind scheme implemented. We include four models with $\alpha=0.5$ (yellow), $\alpha=0.8$ (orange), $\alpha=1.0$ (red), and $\alpha=1.4$ (maroon).