Massive Black Hole Seed Formation in Strong X-Ray Environments at High Redshift

Le résumé fourni par la source

Abstract Direct collapse of pristine gas in early galaxies is a promising pathway for forming supermassive black holes (SMBHs) powering active galactic nuclei at the Epoch of Reionization (EoR). This seeding mechanism requires suppression of molecular hydrogen (H2) cooling during primordial star formation via intense far-ultraviolet radiation from nearby starburst galaxies clustered in overdense regions. However, nondetection of 21 cm signals from the EoR reported by the Hydrogen Epoch of Reionization Array (HERA) experiment suggests that such galaxies may also emit X-rays more efficiently than in the local Universe, promoting H2 production and thereby potentially quenching massive black hole (BH) seed formation. In this study, we examine the thermal and chemical evolution of collapsing gas in dark matter halos using a semi-analytic model incorporating observationally calibrated X-ray intensities. We find that strong X-ray irradiation, as suggested by HERA, significantly suppresses direct collapse and leads most halos to experience H2 cooling. Nevertheless, massive BH seeds with M BH ≳ 104 M ⊙ still form by z ≃ 15, particularly in regions with baryonic streaming motion, and their abundance reaches ∼ 10−4 Mpc−3, sufficient to explain the SMBHs identified by James Webb Space Telescope spectroscopy at 3 < z < 6. While the formation of highly overmassive BHs with masses comparable to their host galaxies is prohibited by X-ray ionization, our model predicts that BH-to-stellar mass ratios of ≃0.01–0.1 were already established at seeding.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.