論文 - 須佐 元
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The Collapse of First Objects driven by Dark Matter Cusps
Masayuki Umemura, Suwa Tamon, Hajime Susa
AIP Conference Proceedings 1238 101 - 106 2010年6月
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DOI： 10.1063/1.3455909
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Radiative Regulation of Population III Star Formation
須佐元
Monthly Notices of the Royal Astronomical Society 2009年11月
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Feedback Effects of First Supernovae on the Neighboring Dark Matter Halos 査読あり
Masaru Sakuma, Hajime Susa
The Astrophysical Journal 698 155 2009年11月
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Cosmological radiative transfer comparison project - II. The radiation-hydrodynamic tests 査読あり
Ilian Iliev et.al.
Monthly Notices of the Royal Astronomical Society 400 ( 3 ) 1283 - 1316 2009年11月
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Formation Criteria and the Mass of Secondary Population III Stars 査読あり
Hajime Susa, Masayuki Umemura, Kenji Hasegawa
The Astrophysical Journal 702 ( 1 ) 480 - 488 2009年11月
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Feedback effects of first supernovae on the neighboring dark matter halos
Sakuma M, Susa H.
Astrophysical Journal 698 ( 1 ) 155 - 162 2009年6月
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The first-generation stars in the Λ cold dark matter universe are considered to have formed in dark halos with total masses in the range ~105-107 M sun at z ~ 20-50. These stars expected to be very massive and in some cases they end their lives as the first supernovae (SNe). We explore the problem of whether star formation in low-mass dark halos (<=107 M sun) was triggered or suppressed by the SN feedback from neighboring star-forming halos. We take into consideration mainly two effects by the SN shock: one is the evacuation of gas components from the halos and the other is the promotion of H2 formation because of the enhanced ionization degree by shock heating. Combining above effects, we find that the star formation activities in the neighboring dark matter halos (M <= 107 M sun) are basically suppressed in case they are located close to the SN center, because of the gas evacuation effect. The critical distance within which the gas is blown away falls within the range ~0.3-1.5 kpc depending on the SN energy and the halo mass. In addition, we find there is very little window in the parameter space where star formation activities in dark halos are induced or promoted by neighboring SN....
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Radiative regulation of population III star formation
Hasegawa K, Umemura M, Susa H.
Monthly Notices of the Royal Astronomical Society 395 ( 3 ) 1280 - 1286 2009年5月
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We explore the impact of ultraviolet (UV) radiation from massive Population III (Pop III) stars of 25, 40, 80 and 120Msolar 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 radiation from the source star can work to impede the secondary star formation through the photoheating and photodissociation processes. Recently, Susa and Umemura have shown that the ionizing radiation alleviates the negative effect by H2-dissociating radiation from 120Msolar Pop III star, since an H2 shell formed ahead of an ionizing front can effectively shield H2-dissociating radiation. On the other hand, it is expected that the negative feedback by H2-dissociating radiation can be predominant if a source star is less massive, since a ratio of the H2-dissociating photon number to the ionizing photon number becomes higher. In order to investigate the radiative feedback effects from such less massive stars, we perform three-dimensional radiation hydrodynamic simulations, incorporating the radiative transfer effect of ionizing and H2-dissociating radiation. As a result, we find that if a source star is less massive than ~25Msolar, the ionizing radiation cannot suppress the negative feedback of H2-dissociating radiation. Therefore, the fate of the neighbouring clouds around such less massive stars is determined solely by the flux of H2-dissociating radiation from source stars. By making analytic estimates of H2 shell formation and its shielding effect, we derive the criteria for radiation hydrodynamic feedback depending on the source star mass....
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FIRST Project: Formation and Feedback of the First Stars
Masayuki Umemura, Hajime Susa, Suwa Tamon, Daisuke Sato
AIP Conference Proceedings 990 386 - 389 2009年3月
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DOI： 10.1063/1.2905587
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Swinyard B, Nakagawa T, Merken P, Royer P, Souverijns T, Vandenbussche B, Waelkens C, Davis P, Di Francesco J, Halpern M, Houde M, Johnstone D, Joncas G, Naylor D, Plume R, Scott D, Abergel A, Bensammar S, Braine J, Buat V, Burgarella D, Cais P, Dole H, Duband L, Elbaz D, Gerin M, Giard M, Goicoechea J, Joblin C, Jones A, Kneib J.P, Lagache G, Madden S, Pons R, Pajot F, Rambaud D, Ravera L, Ristorcelli I, Rodriguez L, Vives S, Zavagno A, Geis N, Krause O, Lutz D, Poglitsch A, Raab W, Stegmaier J, Sturm E, Tuffs R, Lee H.M, Koo B.-C, Im M, Pak S, Han W, Park J.-H, Nam U.-W, Jin H, Lee D.-H, Yuk I.-S, Lee S, Aikawa Y, Arimoto N, Doi Y, Enya K, Fukagawa M, Furusho R, Hasegawa S, Hayashi M, Honda M, Ida S, Imanishi M, Inutsuka S.-I, Izumiura H, Kamaya H, Kaneda H, Kasuga T, Kataza H, Kawabata K, Kawada M, Kawakita H, Kii T, Koda J, Kodama T, Kokubo E, Komatsu K, Matsuhara H, Matsumoto T, Matsuura S, Miyata T, Murakam H, Nagata H, Nagata T, Nakajima T, Naoto K, Nishi R, Noda A, Okamoto A, Okamoto Y.K, Omukai K, Onaka T, Ootsubo T, Ouchi M, Saito H, Sato Y, Sako S, Sekiguchi T, Shibai H, Sugita H, Sugitani K, Susa H, Tae-soo P, Tamura M, Ueda Y, Ueno M, Wada T, Watanabe J, Yamada T, Yamamura I, Yoshida N, Yoshimi K, Yui Y, Benedettini M, Cerulli R, Di Giorgio A, Molinari S, Orfei R, Pezzuto S, Piazzo L, Saraceno P, Spinoglio L, de Graauw T, de Korte P, Helmich F, Hoevers H, Huisman R, Shipman R, van der Tak F, van der Werf P, Wild W, Acosta-Pulido J, Cernicharo J, Herreros J, Martin-Pintado J, Najarro F, Perez-Fourmon I, Pardo J.R, Gomez F, Rodriguez N.C, Ade P, Barlow M, Clements D, Ferlet M, Fraser H, Griffin D, Griffin M, Hargrave P, Isaak K, Ivison R, Mansour M, Laniesse J, Mauskopf P, Morozov D, Oliver S, Orlando A, Page M, Popescu C, Serjeant S, Sudiwala R, Rigopoulou D, Walker I, White G, Viti S, Winter B, Bock J, Bradford M, Harwit M, Holmes W.
Experimental Astronomy 23 ( 1 ) 193 - 219 2009年3月
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The Space Infrared telescope for Cosmology and Astrophysics (SPICA) is planned to be the next space astronomy mission observing in the infrared. The mission is planned to be launched in 2017 and will feature a 3.5 m telescope cooled to <5 K through the use of mechanical coolers. These coolers will also cool the focal plane instruments thus avoiding the use of consumables and giving the mission a long lifetime. SPICA’s large, cold aperture will provide a two order of magnitude sensitivity advantage over current far infrared facilities (>30 microns wavelength). We describe the scientific advances that will be made possible by this large increase in sensitivity and give details of the mission, spacecraft and focal plane conceptual design....
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Regulated star formation in forming disk galaxies exposed to the
須佐元
Astrophysical Journal Volume 684 ( 226 ) 2008年11月
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Regulated star formation in forming disk galaxies exposed to the ultraviolet radiation background
Susa H.
Astrophysical Journal 684 ( 1 ) 226 - 235 2008年9月
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We perform radiation hydrodynamics simulations on the evolution of galactic gas disks irradiated by the ultraviolet radiation background. We find that gas disks with NHgtrsim 1021 cm-2 that are exposed to ultraviolet radiation at a level of I21 = 1 can be self-shielded from photoheating, whereas disks with NHlesssim 1021 cm-2 cannot. We also find that the unshielded disks keep a smooth density distribution without any sign of fragmentation, while the self-shielded disks easily fragment into small pieces through self-gravity, possibly followed by star formation. The suppression of star formation in unshielded disks is different from the photoevaporation effect, since the assumed dark halo potential is deep enough to retain the photoheated gas. The presence of such a critical threshold column density would be one of the reasons for the so-called downsizing feature of present-day galaxies....
DOI： 10.1086/589964
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High Resolution P3M-GRAPE-SPH Simulations of PopIII Star Formation
Suwa Tamon, Masayuki Umemura, Daisike Sato, Hajime Susa,
AIP Conference Proceedings 990 390 - 392 2008年3月
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DOI： 10.1063/1.2905588
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Radiative Transfer SPH Simulations of UV Feedback on Pop III Star Formation
Daisike Sato, Masayuki Umemura, Hajime Susa, Suwa Tamon
AIP Conference Proceedings 990 393 - 394 2008年3月
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DOI： 10.1063/1.2905589
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Radiative transfer SPH Simulations of UV feedback on pop III star formation
Sato D, Umemura M, Susa H, Suwa T.
AIP Conference Proceedings 990 393 - 394 2008年3月
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To explore the radiative feedback from first stars on the subsequent Pop III star formation in a Lambda-CDM universe, we perform high-resolution cosmological SPH simulations coupled with radiative transfer of UV radiation, using FIRST simulator. In the simulations, the baryon mass resolution is 0.3 Msolar and the number of particles is several 105 respectively for baryon and dark matter component. We assume that several collapsing cores form in a Pop III object and one of them evolves into a first star, and then investigate the evolution of other collapsing cores with paying special attention to the radiation hydrodynamic feedback. As a result, it is shown that other collapsing cores are impervious to the negative radiative feedbacks of H2 photodissociation and photoevapolation, but can continue to collapse due to the shielding of UV radiation, consistent with the results of Susa & Umemura (2006). This result implies that all collapsing cores in a Pop III object can evolve into stars....
DOI： 10.1063/1.2905589
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Instability of Population III Black Hole Accretion Disks 査読あり
Ken Ohsuga, Hajime Susa, Yosuke Uchiyama
Publications of the Astronomical Society of Japan 59 ( 6 ) 1235 - 1241 2007年12月
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Instability of population III black hole accretion disks
Ohsuga K, Susa H, Uchiyama Y.
Publications of the Astronomical Society of Japan 59 ( 6 ) 1235 - 1241 2007年12月
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We investigated the stability of black hole accretion disks in a primordial environment (POP III disks for short), by solving the vertical structure of optically thick disks, including convective energy transport, and by employing a one-zone model for optically thin isothermal disks. Because of the absence of metals in POP III disks, we find significant differences in stability associated with ionization between POP III disks and the disks of solar metallicity. An unstable branch in S-shaped equilibrium curves on the dot{M} - Σ (mass accretion rate-surface density) plane extends to a larger surface density compared with the case of disks of solar metallicity. The resulting equilibrium loci indicate that quasi-periodic oscillations in luminosity can also be driven in POP III disks, and their maximal luminosity is typically by an order of magnitude larger than that of the disks of solar metallicity. Such a strong outburst of POP III disks can be observed by future huge telescopes, in the case that the mass is supplied onto the disks at the Bondi accretion rates in typical virialized small dark halos....
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Dissipation of Magnetic Flux in Primordial Star Formation: From Run-away phase to Mass Accretion Phase
須佐元
Publication of Astronomical Society of Japan Volume 59 ( 787 ) 2007年11月
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Photodissociation feedback of Population III stars on their neighbor prestellar cores
須佐元
Astrophysical Journal Volume 659 ( 908 ) 2007年11月
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Dissipation of Magnetic Flux in Primordial Star Formation: From Run-away Phase to Mass-Accretion Phase
須佐 元
Publications of the Astronomical Society of Japan 2007年8月
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We investigate the dissipation of magnetic flux in primordial star-forming clouds throughout their collapse including the run-away collapse phase as well as the accretion phase. We solve the energy equation and the non-equilibrium chemical reactions in the collapsing gas, in order to obtain the radial distribution of the ionized fraction during the collapse. As a result, we find the ionized fraction is high enough for the magnetic field to couple with the gas throughout the evolution of the cloud. This result suggests that the jet formation from protostars as well as the activation of magneto-rotational instability in the accretion disk are enabled in the presence of the cosmological seed magnetic flux proposed by Langer et al.(2003)....
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Radiative feedback of POPIII stars 招待あり
Hajime Susa
Published online at http://www.arcetri.astro.it/hisur.sarticle #6 2007年6月
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