Other
Scientific paper
Jan 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008aipc..966...95f&link_type=abstract
RELATIVISTIC ASTROPHYSICS: 4th Italian-Sino Workshop. AIP Conference Proceedings, Volume 966, pp. 95-102 (2008).
Other
Intergalactic Matter, Quasar Absorption And Emission-Line Systems, Lyman Forest, Cosmology, Other Topics On Stellar Systems, Interstellar Medium, Galactic And Extragalactic Objects And Systems, The Universe, Radiative Transfer, Scattering, Star Formation
Scientific paper
The 21 cm signals from the UV photon sources of reionization epoch is investigated with solving the radiative transfer equation by the WENO algorithm. The results 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. At redshift 1+z = 20, for a UV ionizing source with an intensity Ė~=1045 erg s-1 and a power law spectrum ν-α with α = 2, the emission region has a comoving size of 1-3 Mpc at the age of the source to be ~=2 Myr. However, the emission regions are very small, and would even be erased by thermal broadening if the source satisfies one of the following conditions: 1. the intensity is less than Ė~=1043 erg s-1 2. the frequency spectrum is thermal at temperature T~=105 K, and 3. the frequency spectrum is a power law with α>=3. On the other hand, the 21 cm absorption regions are developed in all these cases. 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.
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