TY - JOUR
T1 - Primordial star formation under the influence of far ultraviolet radiation
T2 - 1540 cosmological haloes and the stellar mass distribution
AU - Hirano, S.
AU - Hosokawa, T.
AU - Yoshida, N.
AU - Omukai, K.
AU - Yorke, H. W.
N1 - Funding Information:
We thank Masahiro M. Machida, Hajime Susa, Kenji Hasegawa, and Kohei Inayoshi for stimulating discussions. We also thank the anonymous referee, whose careful comments improved the clarity of this paper. The numerical calculations were carried out on Cray XC30 and the general-purpose PC farm at Center for Computational Astrophysics, CfCA, of National Astronomical Observatory of Japan, T2K-Tsukuba System at Center for Computational Sciences, University of Tsukuba, and SR16000 at YITP in Kyoto University. This work was supported by Grant-in-Aid for JSPS Fellows (SH) and by the Grants-in-Aid for Basic Researches by the Ministry of Education, Science and Culture of Japan (25800102: TH, 25287050: NY). Portions of this research were conducted at the Jet Propulsion Laboratory, California Institute of Technology, operating under a contract with the National Aeronautics and Space Administration (NASA).
Publisher Copyright:
© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2015/3/21
Y1 - 2015/3/21
N2 - We perform a large set of cosmological simulations of early structure formation and follow the formation and evolution of 1540 star-forming gas clouds to derive the mass distribution of primordial stars. The star formation in our cosmological simulations is characterized by two distinct populations, the so-called Population III.1 stars and primordial stars formed under the influence of far-ultraviolet (FUV) radiation (Population III.2D stars). In this work, we determine the stellar masses by using the dependences on the physical properties of star-forming cloud and/or the external photodissociating intensity from nearby primordial stars, which are derived from the results of 2D radiation hydrodynamic simulations of protostellar feedback. The characteristic mass of the Pop III stars is found to be a few hundred solarmasses at z ~25, and it gradually shifts to lower masses with decreasing redshift. At high redshifts z > 20, about half of the star-forming gas clouds are exposed to intense FUV radiation and thus give birth to massive Pop III.2D stars. However, the local FUV radiation by nearby Pop III stars becomes weaker at lower redshifts, when typical Pop III stars have smaller masses and the mean physical separation between the stars becomes large owing to cosmic expansion. Therefore, at z < 20, a large fraction of the primordial gas clouds host Pop III.1 stars. At z ≲ 15, the Pop III.1 stars are formed in relatively cool gas clouds due to efficient radiative cooling by H2 and HD molecules; such stars have masses of a few × 10M⊙. Since the stellar evolution and the final fate are determined by the stellar mass, Pop III stars formed at different epochs play different roles in the early universe.
AB - We perform a large set of cosmological simulations of early structure formation and follow the formation and evolution of 1540 star-forming gas clouds to derive the mass distribution of primordial stars. The star formation in our cosmological simulations is characterized by two distinct populations, the so-called Population III.1 stars and primordial stars formed under the influence of far-ultraviolet (FUV) radiation (Population III.2D stars). In this work, we determine the stellar masses by using the dependences on the physical properties of star-forming cloud and/or the external photodissociating intensity from nearby primordial stars, which are derived from the results of 2D radiation hydrodynamic simulations of protostellar feedback. The characteristic mass of the Pop III stars is found to be a few hundred solarmasses at z ~25, and it gradually shifts to lower masses with decreasing redshift. At high redshifts z > 20, about half of the star-forming gas clouds are exposed to intense FUV radiation and thus give birth to massive Pop III.2D stars. However, the local FUV radiation by nearby Pop III stars becomes weaker at lower redshifts, when typical Pop III stars have smaller masses and the mean physical separation between the stars becomes large owing to cosmic expansion. Therefore, at z < 20, a large fraction of the primordial gas clouds host Pop III.1 stars. At z ≲ 15, the Pop III.1 stars are formed in relatively cool gas clouds due to efficient radiative cooling by H2 and HD molecules; such stars have masses of a few × 10M⊙. Since the stellar evolution and the final fate are determined by the stellar mass, Pop III stars formed at different epochs play different roles in the early universe.
KW - Dark ages
KW - First stars
KW - Mass function
KW - Methods: numerical
KW - Reionization
KW - Stars: Population III
KW - Stars: formation
KW - Stars: luminosity function
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U2 - 10.1093/mnras/stv044
DO - 10.1093/mnras/stv044
M3 - Article
AN - SCOPUS:85015638824
VL - 448
SP - 568
EP - 587
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 1
ER -