The Epoch of IGM heating by early sources of X-rays

Understand

Observations of the 21 cm line from neutral hydrogen indicate that an Epoch of Heating (EoH) might have preceded the later Epoch of Reionization (EoR).

• Here we study the effects on the ionization state and the thermal history of the Intergalactic Medium (IGM) during the EoH induced by different assumptions on ionizing sources in the high redshift Universe: (i) stars, (ii) X-ray binaries (XRBs), (iii) thermal bremsstrahlung of the hot Interstellar Medium (ISM), and (iv) accreting nuclear black holes (BHs).
• To this aim, we post-process outputs from the ($100 h^{-1}$ cMpc)$^3$ hydrodynamical simulation MassiveBlack-II with the cosmological 3D radiative transfer code CRASH, which follows the propagation of UV and X-ray photons, computing the thermal and ionization state of hydrogen and helium through the EoH.
• We find that stars determine the fully ionized morphology of the IGM, while the spectrally hard XRBs pave way for efficient subsequent heating and ionization by the spectrally softer ISM.