Kazuyuki Omukai

Blue-tilted spectral running and the JWST early galaxy tension

Mikage U. Kobayashi, Gen Chiaki, Kazutaka Kimura, Kazuyuki Akitsu et autres

Recently, the James Webb Space Telescope (JWST) collaboration has found the unexpectedly large abundance of massive galaxies with stellar masses of $\sim 10^{10}~M_{\odot}$ at high redshifts $z \simeq 6.5 - 9$ compared with the prediction of the standard $Λ$CDM model. As a …

Blue-tilted spectral running and the JWST early galaxy tension

Mikage U. Kobayashi, Gen Chiaki, Kazutaka Kimura, Kazuyuki Akitsu et autres

Recently, the James Webb Space Telescope (JWST) collaboration has found the unexpectedly large abundance of massive galaxies with stellar masses of $\sim 10^{10}~M_{\odot}$ at high redshifts $z \simeq 6.5 - 9$ compared with the prediction of the standard $Λ$CDM model. As a …

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An Explicit M1 Radiation-hydrodynamics Scheme for 3D Protostellar Evolution

Kazutaka Kimura, Kazuyuki Sugimura, Takashi Hosokawa, Hajime Fukushima et autres

Abstract We present a radiation-hydrodynamics (RHD) scheme that enables 3D simulations resolving both protostellar interiors and their surrounding accretion flows within a single framework, to clarify how a protostar evolves while interacting with the accretion flow. The method builds on an explicit …

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

Kazutaka Kimura, Kohei Inayoshi, Kazuyuki Omukai

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 …

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

Kazutaka Kimura, Kohei Inayoshi, Kazuyuki Omukai

Direct collapse of pristine gas in early galaxies is a promissing pathway for forming supermassive black holes (BHs) powering active galactic nuclei (AGNs) at the epoch of reionization (EoR). This seeding mechanism requires suppression of molecular hydrogen (H$_2$) cooling during primordial star …

Formation of supermassive stars and dense star clusters in metal-poor clouds exposed to strong FUV radiation

Sunmyon Chon, Kazuyuki Omukai

ABSTRACT The direct-collapse scenario, which predicts the formation of supermassive stars (SMSs) as precursors to supermassive black holes (SMBHs), has been explored primarily under the assumption of metal-free conditions. However, environments exposed to strong far-ultraviolet (FUV) radiation, which is another requirement for …

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Formation of supermassive stars and dense star clusters in metal-poor clouds exposed to strong FUV radiation

Sunmyon Chon, Kazuyuki Omukai

The direct collapse scenario, which predicts the formation of supermassive stars (SMSs) as precursors to supermassive black holes (SMBHs), has been explored primarily under the assumption of metal-free conditions. However, environments exposed to strong far-ultraviolet (FUV) radiation, which is another requirement for …

Impact of the Lyα radiation force on super-Eddington accretion on to a massive black hole

Takuya Mushano, Takumi Ogawa, Ken Ohsuga, Hidenobu Yajima et autres

Abstract The viability of super-Eddington accretion remains a topic of intense debate, crucial for understanding the formation of supermassive black holes in the early universe. However, the impact of the Ly$\alpha$ radiation force on this issue remains poorly understood. We investigate the …

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Impact of Ly$α$ radiation force on super-Eddington accretion onto a massive black hole

Takuya Mushano, Takumi Ogawa, Ken Ohsuga, Hidenobu Yajima et autres

The viability of super-Eddington accretion remains a topic of intense debate, crucial for understanding the formation of supermassive black holes in the early universe. However, the impact of Ly$α$ radiation force on this issue remains poorly understood. We investigate the propagation of …

Gravitational collapse at low to moderate Mach numbers: The relationship between star formation efficiency and the fraction of mass in the massive object

Jorge Saavedra-Bastidas, D. R. G. Schleicher, Ralf S. Klessen, Sunmyon Chon et autres

The formation of massive objects via gravitational collapse is relevant both for explaining the origin of the first supermassive black holes and in the context of massive star formation. Here, we analyze simulations of the formation of massive objects pursued by different …

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The Impact of Stellar Radiative Feedback on Formation of Young Massive Clusters via Fast H i Gas Collisions

Ryunosuke Maeda, Tsuyoshi Inoue, Kazuyuki Omukai, Y. Fukui et autres

Abstract Young massive clusters (YMCs) are dense aggregates of young stars and are often speculated as potential precursors to globular clusters. However, the formation mechanism of massive and compact gas clumps that precede YMCs remains unknown. In this paper, we study the …

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First star formation in extremely early epochs

Mana Ito, Kazuyuki Omukai

Abstract First stars play crucial roles in the development of the Universe, influencing events like cosmic reionization and the chemcal enrichment of the intergalactic medium. While first stars are conventionally thought to form at around $z \sim 20$–30 in the standard $\Lambda$ …

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