The 21-cm signature of early relic H ii regions |
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Authors: | Midori Tokutani Naoki Yoshida S. Peng Oh Naoshi Sugiyama |
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Affiliation: | Department of Physics, Nagoya University, Furocho, Nagoya, Aichi 464-8602, Japan;Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8568, Japan;Department of Physics, University of California, Santa Barbara, CA 93106, USA |
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Abstract: | We calculate the spin temperature and 21-cm brightness of early H ii regions around the first stars. We use outputs from cosmological radiation-hydrodynamics simulations of the formation and evolution of early H ii regions. In the pre-re-ionization era, H ii regions around massive primordial stars have diameters of a few kpc. The gas within the H ii regions is almost fully ionized, but begins recombining after the central stars die off. The relic H ii regions are then seen as bright emission sources in hydrogen 21 cm. We make brightness temperature maps of the H ii regions, accounting for radiative coupling with Lyman α photons in a simplified manner. The spin temperature in the relic H ii region is close to the gas kinetic temperature, generally several hundred to several thousand degrees. We show that the relic H ii region can be as bright as δ T b∼ 100 mK in differential temperature against the cosmic microwave background for an angular resolution of subarcseconds. While individual early H ii patches will not be identified by currently planned radio telescopes, the collective fluctuations from early H ii regions might imprint signatures in the 21-cm background. |
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Keywords: | intergalactic medium cosmology: theory early Universe |
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