Credit: Ewald Puchwein and the Sherwood-Relics collaboration.
The temperature of the intergalactic medium in our hybrid radiative transfer/hydrodynamical simulations during cosmic reionization at redshift 7, performed as part of the Sherwood-Relics project. Cold neutral regions are shown in dark blue. Regions that have been photoionized and heated by the UV emission of first galaxy populations are shown in orange, yellow, green and light blue shades depending on their exact temperature. Very hot shock-heated gas in collapsed structures such as cosmic filaments and halos is shown in red.