Probing the nature of dark matter through the metal enrichment of the intergalactic medium

We focus on exploring the metal enrichment of the intergalactic medium (IGM) in cold and warm (1.5 and 3 keV) dark matter (DM) cosmologies, and the constraints this yields on the DMparticle mass, using a semi-analytic model, DELPHI, that jointly tracks theDMand baryonic assembly of galaxies at z ≃ 4-20 including both supernova (SN) and (a range of) reionization feedback (models). We find that while MUV ≳ -15 galaxies contribute half of all IGM metals in the cold dark matter (CDM) model by z ≃ 4.5, given the suppression of low-mass haloes, larger haloes with MUV ≲ -15 provide about 80 per cent of the IGM metal budget in 1.5 keV warm dark matter (WDM) models using two different models for the metallicity of the interstellar medium. Our results also show that the only models compatible with two different high-redshift data sets, provided by the evolving ultraviolet luminosity function (UV LF) at z ≃ 6-10 and IGM metal density, are standard CDM and 3 keV WDM that do not include any reionization feedback; a combination of the UV LF and the Díaz et al. point provides a weaker constraint, allowing CDM and 3 and 1.5 keV WDM models with SN feedback only, as well as CDM with complete gas suppression of all haloes with vcirc ≲ 30 km s-1. Tightening the error bars on the IGM metal enrichment, future observations, at z ≳ 5.5, could therefore represent an alternative way of shedding light on the nature of DM.