2014/06/30 by Raghunath Ghara, Tirthankar Roy Choudhury, T. Roy Choudhury +1 · 1 citation
Physics and Astronomy · #Amplitude #Astronomy #Astrophysics #Brightness #Brightness temperature #COSMIC cancer database #Cosmic background radiation #Cosmic microwave background #Cosmology and Gravitation Theories #Dark Ages #Galaxies: Formation, Evolution, Phenomena #Galaxy #Physics #Quantum mechanics #Radiative transfer #Radio Astronomy Observations and Technology #Redshift #Reionization #Spectral density #Spectral line #Stars #astro-ph.CO
paper · pdf · doi:10.1093/mnras/stu2512
published as 2015, MNRAS, 447, 1806G · 23 pages, 21 figures, Accepted for publication in MNRAS. Added a section accounting for reionization sources in small haloes
arxiv created 2014/12/16 · openalex publication_date 2015/01/02 · arxiv updated 2015/02/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The 21 cm brightness temperature δTb fluctuations from reionization promise to provide information on the physical processes during that epoch. We present a formalism for generating the δTb distribution using dark matter simulations and a 1D radiative transfer code. Our analysis is able to account for the spin temperature TS fluctuations arising from inhomogeneous X-ray heating and Lyα coupling during cosmic dawn. The δTb power spectrum amplitude at large scales (k ∼ 0.1 Mpc−1) is maximum when ∼10 per cent of the gas (by volume) is heated above the cosmic microwave background temperature. The power spectrum shows a ‘bump’-like feature during cosmic dawn and its location measures the typical sizes of heated regions. We find that the effect of peculiar velocities on the power spectrum is negligible at large scales for most part of the reionization history. During early stages (when the volume averaged ionization fraction ≲ 0.2) this is because the signal is dominated by fluctuations in TS. For reionization models that are solely driven by stars within high-mass (≳ 109 M⊙) haloes, the peculiar velocity effects are prominent only at smaller scales (k ≳ 0.4 Mpc−1) where patchiness in the neutral hydrogen density dominates the signal. The conclusions are unaffected by changes in the amplitude or steepness in the X-ray spectra of the sources.