Cutoff in the Lyman- α forest power spectrum: Warm IGM or warm dark matter?

We re-analyse high redshift and high resolution Lyman- forest spectra considered in 1, seeking to constrain the properties of warm dark matter particles. Compared to this previous work, we consider a wider range of thermal histories of the intergalactic medium. We find that both warm and cold dark matter models can explain the cut-off observed in the flux power spectra of high-resolution observations equally well. This implies, however, very different thermal histories and underlying reionization models. We discuss how to remove this degeneracy.