論文 - 須佐 元
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Blocking Metal Accretion onto Population III Stars by Stellar Wind 査読あり
Tanaka, Shuta J.; Chiaki, Gen; Tominaga, Nozomu; Susa, Hajime
The Astrophysical Journal 844 ( 2 ) id.137 2017年8月
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Formation environment of Pop II stars affected by the feedbacks from Pop III stars
Chiaki G, Susa H, Hirano S.
Memorie della Societa Astronomica Italiana - Journal of the Italian Astronomical Society 88 ( 4 ) 856 - 857 2017年
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Stars with metallicities abH Fe < -3 are called extremely metal-poor (EMP) stars, and considered to be formed in clouds enriched with metal from a single or several supernovae (SNe) of the first-generation (Pop III) stars. To confirm this, we numerically follow the enrichment process of minihalos (MHs) which have hosted Pop III stars. During their main-sequence (MS), the ionizing photons can not or partly break the gas around the Pop III stars because the halo binding energy is marginally larger than the radiation energy. After SN explosions, the gas continues to accrete along filaments of the large-scale structures, and the gas collapses again in the MHs within ̃ 10 Myr for low-mass MHs (3E 5 M☉) while ̃ 1 Myr for massive MHs (3E 6 M☉). The metallicity in the recollapsing regions is 10-4-10-2 Z☉ /SUB> and 10-6-10-5 Z<SUB>☉, respectively. This indicates that EMP stars are formed in the clouds enriched by a single SN in low-mass MHs....
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Stellar wind prevents the ISM gas from accreting onto the Pop III stars
Susa H, Tanaka S, Chiaki G, Tominaga N.
Memorie della Societa Astronomica Italiana 88 ( 4 ) 862 - 863 2017年
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Hyper Metal Poor (HMP) stars in our Galactic halo are often interpreted as the population III (pop III) stars covered by a slight amount of accreted heavy elements from ISM. However, in the case of the Sun, the solar wind maintains the heliosphere which prevents the ISM gas from accreting. We assess the effects of the stellar wind from main sequence pop III stars on the metal accretion onto the surface of them. As a result, we find the heavy elements are ionized by the stellar radiation to be picked up by the stellar wind, thus they cannot touchdown the stellar surface. This result strongly suggests that the HMP stars were born from the gas with a slight amount of metals, which preserves the information of the progenitor stars....
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Dissipation of Magnetic Fields in Star-forming Clouds with Different Metallicities 査読あり
Susa, Hajime; Doi, Kentaro; Omukai, Kazuyuki
The Astrophysical Journal 801 ( 1 ) id.13 2015年3月
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On the IMF of first stars 査読あり
Susa, H.; Hasegawa, K.; Tominaga, N.
AIP Conference Proceedings 1594 ( 1 ) 105 - 108 2014年5月
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Modeling Line-Driven Disk Wind for Broad Absorption Lines of Quasars 査読あり
Nomura, Mariko; Ohsuga, Ken; Wada, Keiichi; Susa, Hajime; Misawa, Toru
Publications of the Astronomical Society of Japan 65 ( 2 ) id.40 2014年4月
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DOI： 10.1093/pasj/65.2.40
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Generation of Magnetic Field on the Accretion Disk around a Proto-first-star 査読あり
Shiromoto, Yuki; Susa, Hajime; Hosokawa, Takashi
The Astrophysical Journal 782 ( 2 ) id.108 2014年2月
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Fluid simulation of plume head-on collision dynamics during pulsed laser ablation 査読あり
Fujii, R.; Doi, K.; Yokoyama, Y.; Fukuoka, H.; Sugimura, A.; Tominaga, N.; Susa, H.; Umezu, I
Journal of Physics: Conference Series 454 ( 1 ) 9d.012009 2013年8月
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Formation and radiative feedback of first objects and first galaxies 査読あり
Umemura, Masayuki; Susa, Hajime; Hasegawa, Kenji; Suwa, Tamon; Semelin, Benoit
Progress of Theoretical and Experimental Physics 2012 ( 1 ) id.01A306 2012年10月
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DOI： 10.1093/ptep/pts018
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Radiative feedback from proto-first-stars
Susa, Hajime
FIRST STARS IV - FROM HAYASHI TO THE FUTURE -. AIP Conference Proceedings 1480 67 - 70 2012年9月
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DOI： 10.1063/1.4754330
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Dissipation of magnetic fields in low-metallicity clouds Show affiliations
Doi, Kentaro; Susa, Hajime; Omukai, Kazuyuki
FIRST STARS IV - FROM HAYASHI TO THE FUTURE -. AIP Conference Proceedings 1480 349 - 351 2012年9月
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DOI： 10.1063/1.4754383
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Effects of Photodissociation on the Fragmentation of Accretion Disk around Proto First Stars
Susa, H
ASP Conference Proceedings 458 81 2012年8月
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Effects of Photodissociation on the Fragmentation of Accretion Disk around Proto First Stars
須佐 元
Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way 2012年8月
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Very recently, the final stages of the first star formation have been investigated intensively. At such stages, an accretion disk is formed around the very first seed of a proto-star, and they seem to fragment inevitably. As a result, it might be possible for sub-solar mass first stars to form from such fragments. However, most of the previous numerical studies did not include the effects of photodissociating radiation from the first proto-stars, which could suppress the fragmentation of the disk. In this paper we include the transfer of Lyman-Werner photons to assess the effects of photodissociation on the fragmentation of the accretion disk. Consequently, we find that the dissociating radiation tends to suppress the mass accretion, but it cannot quench the fragmentation process....
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Line-Driven Disk Wind Model for BALQSOs
須佐 元
AGN Winds in Charleston 2012年8月
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We investigate the conditions for which the line-driven disk wind model reproduces broad absorption line (BAL) features. We research the structure of the disk wind using non-hydrodynamic calculations for a wide range of the parameters. We compare the resulting wind structure with the wind properties of X-ray observations of BAL quasars. We find that the probability that the BAL is observed is large for large black hole mass and large Eddington ratio. When the density of gas at the wind-base is the same as that of the broad emission-line region (BELR), the disk wind model can reproduce BAL features. Our results support the new hypothesis that the wind-base is the BELR....
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SPH Radiative Hydrodynamics Methods 招待あり 査読あり
Hajime Susa
Proceedings of the International Astronomical Union 6 195 - 202 2011年4月
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SPH radiative hydrodynamics methods
Susa H.
Proceedings of the International Astronomical Union 6 ( S270 ) 195 - 202 2011年4月
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In this paper, we review the radiative hydrodynamics methods based upon Smoothed Particle Hydrodynamics(SPH). There are already various implementations so far, which can be categorized into three types: moment equation solvers, Monte Carlo methods, and ray-tracing schemes. These codes have been applied to various astrophysical problems including dynamics of dense proto-stellar cores, photoionization feedback of massive stars on molecular clouds, radiative feedback in the early universe, etc. Among these different methods, we focus on the ray-tracing schemes. We also describe one particular ray-tracing code RSPH in some details....
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Generation of Seed Magnetic Field Around First Stars: Effects of Radiation Force 査読あり
Masashi Ando, Kentaro Doi, Hajime Susa
The Astrophysical Journal 716 ( 2 ) 1566 - 1572 2010年11月
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Generation of Magnetic Fields by Radiation Pressure from the First Stars
Hajime Susa, Masashi Ando, Kentaro Doi
AIP Conference Proceedings 1294 291 - 292 2010年11月
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Generation of magnetic fields by radiation pressure from the first stars
Susa H, Ando M, Doi K.
AIP Conference Proceedings 1294 291 - 292 2010年11月
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We investigate seed magnetic field generation by radiation pressure from the first stars. We include induction effects by electromagnetic fields, which were not taken into account previously. As a result, we find much smaller magnetic fields than predicted by the static H II regions assumed in our earlier models, even if momentum transfer due to photoionizations, which were excluded from our previous work, is present. The resultant magnetic flux density around the first star is as large as 10-20 G. These seed magnetic field will not affect subsequent star formation in the neighborhood of the first stars....
DOI： 10.1063/1.3518883
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Generation of Seed Magnetic Field around First Stars
Masashi Ando, Kentaro Doi, Hajime Susa
AIP Conference Proceedings 1238 133 - 135 2010年6月
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DOI： 10.1063/1.3455916