We pass a sightline through a hydrodynamical simulation of a galaxy and build the corresponding absorption spectrum zoomed in on the Si II 1260 Angstrom feature. This uses the Trident synthetic spectral generation code built on top of yt.
On the left, you see a 2D slice of the simulation volume centered on an ~L* galaxy at z=0.2. On the right, you see the Si II density and line-of-sight velocity of the sightline in the top two panels, and you see the spectrum centered on the Si II 1260 Angstrom feature in the bottom panel. In green is the pure spectrum, whereas the black channel map includes noise (S/N = 10), a QSO background source, and a Milky Way foreground.
