Simulations of galaxies formed in warm dark matter halos of masses at the filtering scale (1412.1100v2)

Abstract: We present zoom-in N-body + Hydrodynamic simulations of dwarf central galaxies formed in Warm Dark Matter (WDM) halos with masses at present-day of $2-4\times 10^{10}$ \msun. Two different cases are considered, the first one when halo masses are close to the corresponding half-mode filtering scale \Mhm\ (\mwdm =1.2 keV), and the second when they are 20 to 30 times the corresponding \Mhm\ (\mwdm = 3.0 keV). The WDM simulations are compared with the respective Cold Dark Matter (CDM) simulations. The dwarfs formed in halos of masses (20-30)\Mhm have roughly similar properties and evolution than their CDM counterparts; on the contrary, those formed in halos of masses around \Mhm, are systematically different from their CDM counterparts. As compared to the CDM dwarfs, they assemble the dark and stellar masses later, having mass-weighted stellar ages 1.4--4.8 Gyr younger; their circular velocity profiles are shallower, with maximal velocities 20--60% lower; their stellar distributions are much less centrally concentrated and with larger effective radii, by factors 1.3--3. The WDM dwarfs at the filtering scale (\mwdm =1.2 keV) have disk-like structures, and end in most cases with higher gas fractions and lower stellar-to-total mass ratios than their CDM counterparts. The late halo assembly, low halo concentrations, and the absence of satellites of the former with respect to the latter, are at the basis of the differences.