The observational signature of the first H ii regions |
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Authors: | Thomas H Greif † Jarrett L Johnson Ralf S Klessen Volker Bromm |
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Institution: | Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Straße 2, 69120 Heidelberg, Germany;Department of Astronomy, University of Texas, Austin, TX 78712, USA;Texas Cosmology Center, University of Texas, Austin, TX 78712, USA |
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Abstract: | We use three-dimensional smoothed particle hydrodynamics simulations together with a dynamical ray-tracing scheme to investigate the build-up of the first H ii regions around massive Population III stars in minihaloes. We trace the highly anisotropic breakout of the ionizing radiation into the intergalactic medium, allowing us to predict the resulting recombination radiation with greatly increased realism. Our simulations, together with Press–Schechter type arguments, allow us to predict the Population III contribution to the radio background at ~100 MHz via bremsstrahlung and 21-cm emission. We find a global bremsstrahlung signal of around 1 mK , and a combined 21-cm signature which is an order of magnitude larger. Both might be within the reach of the planned Square Kilometer Array experiment, although detection of the free–free emission is only marginal. The imprint of the first stars on the cosmic radio background might provide us with one of the few diagnostics to test the otherwise elusive minihalo star formation site. |
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Keywords: | stars: formation cosmology: observations cosmology: theory early Universe |
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