With upcoming high-quality data from surveys such as the Extended Baryon Oscillation Spectroscopic Survey or the Dark Energy Spectroscopic Instrument , improving the theoretical modeling and gaining a deeper understanding of the effects of neutrinos and dark radiation on structure formation at small scales are necessary , to obtain robust constraints free from systematic biases .
Using a novel suite of hydrodynamical simulations that incorporate dark matter , baryons , massive neutrinos , and dark radiation , we present a detailed study of their impact on Lyman- \alpha ( Ly \alpha ) forest observables .
In particular , we accurately measure the tomographic evolution of the shape and amplitude of the small-scale matter and flux power spectra and search for unique signatures along with preferred scales where a neutrino mass detection may be feasible .
We then investigate the thermal state of the intergalactic medium ( IGM ) through the temperature–density relation .
Our findings suggest that at k \sim 5 h { Mpc ^ { -1 } } the suppression on the matter power spectrum induced by \sum m _ { \nu } = 0.1 eV neutrinos can reach \sim 4 \% at z \sim 3 when compared to a massless neutrino cosmology , and \sim 10 \% if a massless sterile neutrino is included ; surprisingly , we also find good agreement ( \sim 2 \% ) with some analytic predictions .
For the 1D flux power spectrum P _ { { \cal { F } } } ^ { 1 D } , the highest response to free-streaming effects is achieved at k \sim 0.005 ~ { } { [ km / s ] ^ { -1 } } when \sum m _ { \nu } = 0.1 eV ; this k -limit falls in the Ly \alpha forest regime , making the small-scale P _ { { \cal { F } } } ^ { 1 D } an excellent probe for detecting neutrino and dark radiation imprints .
Our results indicate that the IGM at z \sim 3 provides the best sensitivity to active and sterile neutrinos .