Here is spectra generated from the same line of sight on Enzo ( left ) and on Cholla ( right ).

The redshift is: \(z=2.35\)

The absorption lines are computed using:

\[\tau_{v}=\frac{\pi e^{2}}{m_{e} c} f_{12} \int \frac{n_{\mathrm{X}}}{\Delta v_{\mathrm{D}}} \frac{\exp \left[-\left(\frac{v-v_{0}}{\Delta {v}_{\mathrm{D}}}\right)^{2}\right]}{\sqrt{\pi}} d r\]

where \(\Delta v_{\mathrm{D}}=(b / c) v_{0}\) is the Doppler width, using the Doppler parameter \(b=b_{\text { thermal }}=\sqrt{2 k_{\mathrm{B}} T / m_{\mathrm{H}}}\).

Here is a better comparison: