Hidenobu Yajima, Yuexing Li, Qirong Zhu, Tom Abel, Caryl Gronwall, Robin Ciardullo
A large number of high-redshift galaxies have been discovered through narrow-band Lya line or broad-band continuum in recent years. The escaping process of photons from these early galaxies is crucial to understanding galaxy evolution and the cosmic reionization. Here, we investigate the escape of Lya, non-ionizing UV-continuum (l = 1300 - 1600 angs in rest frame), and ionizing photons (l < 912 angs) from galaxies by combining cosmological hydrodynamic simulations with three-dimensional multi-wavelength radiative transfer calculations. We find that the escape fraction (fesc) of these different photons shows a complex dependance on redshift and galaxy properties: fesc(Lya) and fesc(UV) appear to evolve with redshift, and they show similar, weak correlations with galaxy properties such as mass, star formation, metallicity, and dust content, while fesc(Ion) remains roughly constant at ~ 0.2 from z ~ 0 - 10, and it does not show clear dependence on the properties of the galaxy. The fesc(Lya) correlates more strongly with fesc(UV) than with fesc(Ion). In addition, we estimate the ionizing photon emissivity of Lyman Alpha Emitters (LAEs) and their contribution to the ionization of intergalactic medium (IGM), by combining our simulations with the observed luminosity functions of LAEs at different redshift. Our result suggests that ionizing photons from LAEs alone are not sufficient to ionize IGM at z > 6, but they can maintain the ionization of IGM at z ~ 0 - 5.
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http://arxiv.org/abs/1209.5842
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