Cutoff in the Lyman-$\alpha$ forest power spectrum: warm IGM or warm dark matter?

TL;DR

This study re-analyzes high-redshift Lyman-alpha forest data to investigate whether the observed power spectrum cutoff is due to warm dark matter or thermal effects in the intergalactic medium, highlighting degeneracies in interpretation.

Contribution

It extends previous analyses by considering a broader range of IGM thermal histories, demonstrating that both warm and cold dark matter models fit the data equally well.

Findings

Both warm and cold dark matter models can explain the observed cutoff.

Different thermal histories can produce similar spectral features.

Degeneracy between dark matter properties and IGM thermal state exists.

Abstract

We re-analyse high redshift and high resolution Lyman-$\alpha$ forest spectra considered in (Viel et al 2013), 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 re-ionisation models. We discuss how to remove this degeneracy.