We introduce a new set of large scale , high resolution hydrodynamical simulations of the intergalactic medium : the Sherwood simulation suite .
These are performed in volumes 10 ^ { 3 } – 160 ^ { 3 } h ^ { -3 } comoving Mpc ^ { 3 } , span almost four orders of magnitude in mass resolution with up to 17.2 billion particles , and employ a variety of physics variations including warm dark matter and galactic outflows .
We undertake a detailed comparison of the simulations to high resolution , high signal-to-noise observations of the Ly \alpha forest over the redshift range 2 \leq z \leq 5 .
The simulations are in very good agreement with the observational data , lending further support to the paradigm that the Ly \alpha forest is a natural consequence of the web-like distribution of matter arising in \Lambda CDM cosmological models .
Only a small number of minor discrepancies remain with respect to the observational data .
Saturated Ly \alpha absorption lines with column densities N _ { HI } > 10 ^ { 14.5 } cm ^ { -2 } at 2 < z < 2.5 are underpredicted in the models .
An uncertain correction for continuum placement bias is required to match the distribution and power spectrum of the transmitted flux , particularly at z > 4 .
Finally , the temperature of intergalactic gas in the simulations may be slightly too low at z = 2.7 and a flatter temperature-density relation is required at z = 2.4 , consistent with the expected effects of non-equilibrium ionisation during He \scriptstyle II reionisation .