Achievements & Publications

Radiation drag driven mass accretion in a clumpy interstellar medium: implications for the supermassive black hole-to-bulge relation

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Kawakatu, Nozomu,   Umemura, Masayuki

We quantitatively scrutinize the effects of the radiation drag arising from the radiation fields in a galactic bulge in order to examine the possibility that the radiation drag could be an effective mechanism to extract angular momentum in a spheroidal system like a bulge and allow plenty of gas to...

A Radiation-Hydrodynamical Model for Supermassive Black Hole-to-Bulge Mass Relation and Quasar Formation

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Umemura, Masayuki

As a potential mechanism to build up supermassive black holes (BHs) in a spheroidal system, we consider the radiation drag effect by bulge stars, which extracts angular momentum from interstellar gas and thus allows the gas to accrete onto the galactic center. By incorporating the radiation hydrodynamical equation with simple...

Criteria for the formation of Population III objects in the ultraviolet background radiation

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Kitayama, T.,   Susa, H.,   Umemura, M.,   Ikeuchi, S.

We explore possibilities of collapse and star formation in Population III objects exposed to the external ultraviolet background (UVB) radiation. Assuming spherical symmetry, we solve self- consistently radiative transfer of photons, non-equilibrium H$_2$ chemistry and gas hydrodynamics. Although the UVB does suppress the formation of low-mass objects, the negative feedback...

Theoretical Models of Multi-Waveband QSO Luminosity Functions

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Hosokawa, Takashi,   Mineshige, Shin,   Kawaguchi, Toshihiro,   Yoshikawa, Kohji,   Umemura, Masayuki

The cosmological evolution of the QSO luminosity functions (LFs) at NIR/optical/X-ray bands for 1.3 <åisebox-0.5ex~ z <\i̊sebox-0.5ex~ 3.5 is discussed based on realistic QSO spectra. The accretion-disk theory predicts that although the QSO luminosities only depend on the mass-accretion rate, dot\M\, the QSO spectra have dependence on the black- hole...

Formation of Obscuring Walls by the Radiation Force from Circumnuclear Starbursts and the Implications for the Starburst-Active Galactic Nucleus Connection

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Ohsuga, Ken,   Umemura, Masayuki

We explore the formation of dusty gas walls induced by a circumnuclear starburst around an active galactic nucleus (AGN). We concentrate our attention on the role of the radiation force of a starburst as well as an AGN, in which the effects of the optical depth of dusty gas are...

Circumnuclear obscuration of the Circinus galaxy by a starburst-radiation supported wall

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Ohsuga, K.,   Umemura, M.

We consider the radiation-hydrodynamical formation of a dusty wall in the circumnuclear regions of the Circinus Seyfert 2 galaxy. We focus on the radiative flux force due to the circumnuclear starburst, the nuclear starburst and the active galactic nucleus (AGN), and analyze the equilibrium configuration and stability of the dusty...

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Radiation drag driven mass accretion in a clumpy interstellar medium: implications for the supermassive black hole-to-bulge relation

Kawakatu, Nozomu,   Umemura, Masayuki

We quantitatively scrutinize the effects of the radiation drag arising from the radiation fields in a galactic bulge in order to examine the possibility that the radiation drag could be an effective mechanism to extract angular momentum in a spheroidal system like a bulge and allow plenty of gas to...

January 2002   Monthly Notices of the Royal Astronomical Society
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A Radiation-Hydrodynamical Model for Supermassive Black Hole-to-Bulge Mass Relation and Quasar Formation

Umemura, Masayuki

As a potential mechanism to build up supermassive black holes (BHs) in a spheroidal system, we consider the radiation drag effect by bulge stars, which extracts angular momentum from interstellar gas and thus allows the gas to accrete onto the galactic center. By incorporating the radiation hydrodynamical equation with simple...

October 2001   The Astrophysical Journal Letters
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Criteria for the formation of Population III objects in the ultraviolet background radiation

Kitayama, T.,   Susa, H.,   Umemura, M.,   Ikeuchi, S.

We explore possibilities of collapse and star formation in Population III objects exposed to the external ultraviolet background (UVB) radiation. Assuming spherical symmetry, we solve self- consistently radiative transfer of photons, non-equilibrium H$_2$ chemistry and gas hydrodynamics. Although the UVB does suppress the formation of low-mass objects, the negative feedback...

October 2001   Monthly Notices of the Royal Astronomical Society
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Theoretical Models of Multi-Waveband QSO Luminosity Functions

Hosokawa, Takashi,   Mineshige, Shin,   Kawaguchi, Toshihiro,   Yoshikawa, Kohji,   Umemura, Masayuki

The cosmological evolution of the QSO luminosity functions (LFs) at NIR/optical/X-ray bands for 1.3 <åisebox-0.5ex~ z <\i̊sebox-0.5ex~ 3.5 is discussed based on realistic QSO spectra. The accretion-disk theory predicts that although the QSO luminosities only depend on the mass-accretion rate, dot\M\, the QSO spectra have dependence on the black- hole...

October 2001   Publications of the Astronomical Society of Japan
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Formation of Obscuring Walls by the Radiation Force from Circumnuclear Starbursts and the Implications for the Starburst-Active Galactic Nucleus Connection

Ohsuga, Ken,   Umemura, Masayuki

We explore the formation of dusty gas walls induced by a circumnuclear starburst around an active galactic nucleus (AGN). We concentrate our attention on the role of the radiation force of a starburst as well as an AGN, in which the effects of the optical depth of dusty gas are...

September 2001   The Astrophysical Journal
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Circumnuclear obscuration of the Circinus galaxy by a starburst-radiation supported wall

Ohsuga, K.,   Umemura, M.

We consider the radiation-hydrodynamical formation of a dusty wall in the circumnuclear regions of the Circinus Seyfert 2 galaxy. We focus on the radiative flux force due to the circumnuclear starburst, the nuclear starburst and the active galactic nucleus (AGN), and analyze the equilibrium configuration and stability of the dusty...

June 2001