Rapidly growing primordial black holes as seeds of the massive high-redshift JWST Galaxies (2303.09391v3)

Abstract: A group of massive galaxies at redshifts of $z\gtrsim 7$ have been recently detected by the James Webb Space Telescope (JWST), which were unexpected to form so early within the framework of standard Big Bang cosmology. In this work, we propose that this puzzle can be explained by the presence of some primordial black holes (PBHs) with a mass of $\sim 1000 M_\odot$. These PBHs, clothed in dark matter halo and undergoing super-Eddington accretion, serve as seeds for the early galaxy formation with masses of $\sim 10^{8}-10^{10}~M_\odot$ at high redshift, thus accounting for the JWST observations. Using a hierarchical Bayesian inference framework to constrain the PBH mass distribution models, we find that the Lognormal model with $M_{\rm c}\sim 750M_\odot$ is preferred over other hypotheses. These rapidly growing BHs are expected to emit strong radiation and may appear as high-redshift compact objects, similar to those recently discovered by JWST. Although we focuse on PBHs in this work, the bound on the initial mass of the seed black holes remains robust even if they were formed through astrophysical channels.

• The paper presents a novel model where rapidly growing primordial black holes serve as seeds for massive high-redshift galaxies.
• It employs a hierarchical Bayesian inference to favor a Lognormal PBH mass distribution with a central mass near 750 M⊙.
• The study demonstrates that super-Eddington accretion enables PBHs to grow from ~1000 M⊙ to 10^8–10^10 M⊙, matching JWST observations.

Understanding Primordial Black Holes as Seeds of High-Redshift Galaxies

This paper, authored by Yuan et al., presents an intriguing hypothesis for the formation of massive high-redshift galaxies observed by the James Webb Space Telescope (JWST). The authors propose that rapidly growing primordial black holes (PBHs) may act as the seeds for the early universe's massive galaxies. This paper explores the dynamics of PBH growth through super-Eddington accretion, utilizing observational data from JWST to validate their theoretical models.

Primordial Black Holes as Cosmic Building Blocks

The research addresses a critical conundrum in contemporary astrophysics: the presence of unexpectedly massive galaxies at redshifts $z \gtrsim 7$ within the cosmological framework governed by the Big Bang model. The paper postulates that this phenomenon can be accounted for by the existence of PBHs with an initial mass of approximately $1000 M_\odot$. These black holes, encapsulated in dark matter halos, could experience dramatic growth through super-Eddington accretion processes, reaching up to $10^8-10^{10} M_\odot$ at high redshifts, thereby explaining the JWST's observations.

Methodology and Model Selection

To substantiate the proposed hypothesis, the paper implements a hierarchical Bayesian inference framework to constrain various models of the PBH mass distribution. Among the considered models—Lognormal, Multipeak, Powerlaw, Gaussian, and Critical—the paper finds the Lognormal distribution to be preferable over others, with a central characteristic mass $M_c \approx 750 M_\odot$. This is evaluated by Bayesian evidence metrics, indicating that the Lognormal model provides the most statistically robust fit to the distribution of PBH masses necessary to align with JWST data.

Numerical Insights and Model Robustness

From a computational perspective, the paper utilizes a detailed analytic accretion model to ascertain the efficacies of PBH mass accretion in the early Universe, factoring in influences such as dark matter halos and accretion feedback mechanisms. Figure 1 of the paper elucidates how PBHs with initial masses $M_{\text{BH, i}}$ can effectively grow under these conditions. The model simulations delineate that only PBHs above a threshold initial mass manage considerable growth, bolstering the theory that PBHs contribute significantly to the formation of massive high-redshift MBHs. The results indicate that even if the seed black holes originated via astrophysical processes rather than primordial formation, the requisite initial mass constraints remain consistent.

Implications for Cosmology and Further Research

Both practical and theoretical implications arise from this paper. Practically, the model suggests that PBHs could significantly influence the background radiation in various spectra, particularly radio and X-ray, offering potential observational signatures for future missions like the Square Kilometre Array (SKA) and the Wide Field Survey Telescope (WFST). Theoretically, the research highlights the necessity for precise statistical analysis in differentiating PBH distribution models, setting a precedent for more refined future constraints with advancements in observational capabilities.

Conclusion

Yuan et al.'s work contributes substantially to the understanding of the early Universe by proposing a plausible mechanism for the rapid formation of massive galaxies in apparent contradiction with the expected timeline of standard cosmology. The paper emphasizes PBHs as not only potential dark matter candidates but also as pivotal cosmic structures, prompting reevaluations of their role within the broader astrophysical context. Future observations from next-generation telescopes could provide further insights and opportunities to validate or refine these initial findings, potentially transforming the landscape of early Universe cosmology.