21 cm signal from cosmic dawn: Imprints of spin temperature fluctuations and peculiar velocities

Understand

The 21 cm brightness temperature $\delta T_{\rm b}$ fluctuations from reionization promise to provide information on the physical processes during that epoch.

• We present a formalism for generating the $\delta T_{\rm b}$ distribution using dark matter simulations and an one-dimensional radiative transfer code.
• Our analysis is able to account for the spin temperature $T_{\rm S}$ fluctuations arising from inhomogeneous X-ray heating and Ly$\alpha$ coupling during cosmic dawn.
• The $\delta T_{\rm b}$ power spectrum amplitude at large scales ($k \sim 0.1$ Mpc$^{-1}$) is maximum when $\sim 10\%$ of the gas (by volume) is heated above the CMB temperature.