Achievements & Publications

Three-dimensional radiative properties of hot accretion flows on to the Galactic Centre black hole

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Kato, Y.,   Umemura, M.,   Ohsuga, K.

By solving the radiative transfer equations, we examine the three- dimensional radiative properties of a magnetohydrodynamic accretion flow model conforming to the observed spectrum of Sgr A* in the vicinity of the supermassive black hole at the Galactic Centre. As a result, we find that the core of the radio...

Cosmological radiative transfer comparison project - II. The radiation-hydrodynamic tests

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Iliev, Ilian T.,   Whalen, Daniel,   Mellema, Garrelt,   Ahn, Kyungjin,   Baek, Sunghye,   Gnedin, Nickolay Y.

The development of radiation hydrodynamical methods that are able to follow gas dynamics and radiative transfer (RT) self- consistently is key to the solution of many problems in numerical astrophysics. Such fluid flows are highly complex, rarely allowing even for approximate analytical solutions against which numerical codes can be tested....

The escape of ionizing photons from supernova-dominated primordial galaxies

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Yajima, Hidenobu,   Umemura, Masayuki,   Mori, Masao,   Nakamoto, Taishi

In order to assess the contribution of Lyman break galaxies (LBGs) and Lyman \ensuremathα emitters (LAEs) at redshifts 3 < z < 7 to the ionization of intergalactic medium (IGM), we investigate the escape fractions of ionizing photons from supernova-dominated primordial galaxies by solving the three- dimensional (3D) radiative transfer....

Formation Criteria and the Mass of Secondary Population III Stars

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Susa, Hajime,   Umemura, Masayuki,   Hasegawa, Kenji

We explore the formation of secondary Population III (Pop III) stars under radiation hydrodynamic (RHD) feedback by a preformed massive star. To properly treat RHD feedback, we perform three- dimensional RHD simulations incorporating the radiative transfer of ionizing photons as well as H$_2$ dissociating photons from a preformed star. A...

Formation of globular clusters induced by external ultraviolet radiation

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Hasegawa, Kenji,   Umemura, Masayuki,   Kitayama, Tetsu

We present a novel scenario for globular cluster (GC) formation, where the ultraviolet (UV) background radiation effectively works so as to produce compact star clusters. Recent observations on the age distributions of GCs indicate that many GCs formed even after the cosmic reionization epoch. This implies that a significant fraction...

Global Radiation-Magnetohydrodynamic Simulations of Black-Hole Accretion Flow and Outflow: Unified Model of Three States

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Ohsuga, Ken,   Mineshige, Shin,   Mori, Masao,   Kato, Yoshiaki

Black-hole accretion systems are known to possess several distinct modes (or spectral states), such as low/hard state, high/soft state, and so on. Since the dynamics of the corresponding flows is distinct, theoretical models were separately discussed for each state. We here propose a unified model based on our new, global,...

Radiative regulation of Population III star formation

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Hasegawa, K.,   Umemura, M.,   Susa, H.

We explore the impact of ultraviolet (UV) radiation from massive Population III (Pop III) stars of 25, 40, 80 and 120M$_solar$ on the subsequent Pop III star formation. In this paper, particular attention is paid to the dependence of radiative feedback on the mass of source Pop III star. UV...

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Three-dimensional radiative properties of hot accretion flows on to the Galactic Centre black hole

Kato, Y.,   Umemura, M.,   Ohsuga, K.

By solving the radiative transfer equations, we examine the three- dimensional radiative properties of a magnetohydrodynamic accretion flow model conforming to the observed spectrum of Sgr A* in the vicinity of the supermassive black hole at the Galactic Centre. As a result, we find that the core of the radio...

December 2009   Monthly Notices of the Royal Astronomical Society
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Cosmological radiative transfer comparison project - II. The radiation-hydrodynamic tests

Iliev, Ilian T.,   Whalen, Daniel,   Mellema, Garrelt,   Ahn, Kyungjin,   Baek, Sunghye,   Gnedin, Nickolay Y.

The development of radiation hydrodynamical methods that are able to follow gas dynamics and radiative transfer (RT) self- consistently is key to the solution of many problems in numerical astrophysics. Such fluid flows are highly complex, rarely allowing even for approximate analytical solutions against which numerical codes can be tested....

December 2009   Monthly Notices of the Royal Astronomical Society
Image

The escape of ionizing photons from supernova-dominated primordial galaxies

Yajima, Hidenobu,   Umemura, Masayuki,   Mori, Masao,   Nakamoto, Taishi

In order to assess the contribution of Lyman break galaxies (LBGs) and Lyman \ensuremathα emitters (LAEs) at redshifts 3 < z < 7 to the ionization of intergalactic medium (IGM), we investigate the escape fractions of ionizing photons from supernova-dominated primordial galaxies by solving the three- dimensional (3D) radiative transfer....

September 2009   Monthly Notices of the Royal Astronomical Society
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Formation Criteria and the Mass of Secondary Population III Stars

Susa, Hajime,   Umemura, Masayuki,   Hasegawa, Kenji

We explore the formation of secondary Population III (Pop III) stars under radiation hydrodynamic (RHD) feedback by a preformed massive star. To properly treat RHD feedback, we perform three- dimensional RHD simulations incorporating the radiative transfer of ionizing photons as well as H$_2$ dissociating photons from a preformed star. A...

September 2009   The Astrophysical Journal
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Formation of globular clusters induced by external ultraviolet radiation

Hasegawa, Kenji,   Umemura, Masayuki,   Kitayama, Tetsu

We present a novel scenario for globular cluster (GC) formation, where the ultraviolet (UV) background radiation effectively works so as to produce compact star clusters. Recent observations on the age distributions of GCs indicate that many GCs formed even after the cosmic reionization epoch. This implies that a significant fraction...

August 2009   Monthly Notices of the Royal Astronomical Society
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Global Radiation-Magnetohydrodynamic Simulations of Black-Hole Accretion Flow and Outflow: Unified Model of Three States

Ohsuga, Ken,   Mineshige, Shin,   Mori, Masao,   Kato, Yoshiaki

Black-hole accretion systems are known to possess several distinct modes (or spectral states), such as low/hard state, high/soft state, and so on. Since the dynamics of the corresponding flows is distinct, theoretical models were separately discussed for each state. We here propose a unified model based on our new, global,...

June 2009   Publications of the Astronomical Society of Japan
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Radiative regulation of Population III star formation

Hasegawa, K.,   Umemura, M.,   Susa, H.

We explore the impact of ultraviolet (UV) radiation from massive Population III (Pop III) stars of 25, 40, 80 and 120M$_solar$ on the subsequent Pop III star formation. In this paper, particular attention is paid to the dependence of radiative feedback on the mass of source Pop III star. UV...

May 2009   Monthly Notices of the Royal Astronomical Society