21 cm Signals from Early Ionizing Sources

Abstract

We investigate the 21 cm signals from the UV ionizing sources in the reionization epoch. The formation and evolution of 21 cm emission and absorption regions depend essentially on the kinetics of photons in the physical and frequency spaces. To solve the radiative transfer equation, we use the WENO algorithm, which is effective to capture the sharp ionization profile and the cut-off at the front of light $(r=ct)$ and to handle the small fraction of neutral hydrogen and helium in the ionized sphere. We show that a spherical shell of 21 cm emission and absorption will develop around a point source once the speed of the ionization front (I-front) is significantly lower than the speed of light. The 21 cm shell extends from the I-front to the front of light; its inner part is the emission region and its outer part is the absorption region. The 21 cm emission region depends strongly on the intensity, frequency-spectrum and life-time of the UV ionizing source. For a source of short life-time, no 21 cm emission region can be formed if the source dies out before the I-front speed is significantly lower than the speed of light. Yet, a 21 cm absorption region can form and develop even after the emission of the source ceases.

25 pages, 9 figures, accepted by ApJ

References in corpus (8)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• Simulating Cosmic Reionization at Large Scales II: the 21-cm Emission Features and Statistical Signals
• The 21 Centimeter Background from the Cosmic Dark Ages: Minihalos and the Intergalactic Medium before Reionization
• Recognizing the First Radiation Sources Through Their 21-cm Signature
• Detection and Fundamental Applications of Individual First Galaxies
• A WENO Algorithm for the Radiative Transfer and Ionized Sphere at Reionization
• A Unified Fitting of HI and HeII LyαTransmitted Flux of QSO HE2347 with LCDM Hydrodynamic Simulations
• A WENO Algorithm of the Temperature and Ionization Profiles around a Point Source

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• Wouthuysen-Field Coupling in the 21 cm Region Around High Redshift Sources
• Time-Dependent Behavior of Lyman$\alpha$ Photon Transfer in High Redshift Optically Thick Medium
• Effect of Dust on Lyman-alpha Photon Transfer in Optically Thick Halo