and masking of faint galaxies well into the dwarf regime . Additionally, even if it will not be possible to mask all of the faint galaxies, the integrated signal would still contain emission from gas that has not been detected before and will therefore still be worth studying.\

![Distribution of the HI 21 cm differential brightness temperature signal as a function of overdensity for cells in the EAGLE simulation, assuming the UV background and after masking cells with a radius of 100 $h^{-1}$kpc around the position of the halos. The cells at the top of the figure, above the main distribution are cells belonging to halos that were not completely masked. The colorbar shows the number of cells.[]{data-label="fig:boxsigdens"}](./images/eagle_denssig_hm01_full_galmask100kpch.pdf){width="49.00000%"}

![image](./images/eagle_slice_1e8galmasscut_dTb_hm01_5mpc_nostar_galmask100kpch_inlay.pdf){width="\textwidth"}

Galaxies and their circumgalactic medium (CGM) contain large amounts of neutral gas, but since we are targetting the HI gas in the IGM, we remove their signal by masking them with a fixed masking radius of 100 $h^{-1}$kpc. We explored the impact of adopting a different radius on the signal and found this radius to effectively remove most of the unwanted signal. Nonetheless, a small amount of contamination still remains from halos that are larger. Properly removing this contamination observationally would 