Variations of Observed Lyman-{\alpha} Spectra Shapes due to the Intergalactic Absorption

Understand

Lyman-$\alpha$ (Ly$\alpha$) spectra provide insights into the small-scale structure and kinematics of neutral hydrogen (HI) within galaxies as well as the ionization state of the intergalactic medium (IGM).

• The former defines the intrinsic spectrum of a galaxy, which is modified by the latter.
• These two effects are degenerate.
• Using the IllustrisTNG100 simulation, we study the impact of the IGM on Ly$\alpha$ spectral shapes between $z\sim 0$ and $5$.