http://arxiv.org/abs/2102.09078
We analyze observations of the mass profiles of 175 late-type galaxies in the Spitzer Photometry \& Accurate Rotation Curves (SPARC) database to construct the temperature profile of their dark matter (DM) halos by assuming that (1) DM in the halos obeys either the Fermi-Dirac or the Maxwell-Boltzmann distribution, and (2) the halos are in the virial state. We derive the dispersion velocity of DM at the center of the halos and show that its correlation with the halo’s total mass is the same as the one estimated in N-body simulations. The correlation is also the same as the observed relation between the two variables for visible matter in galaxies. Taking the latter agreement as a validation of our analysis, we derive the mass to the temperature of DM at the edge of the halos and show that it is galaxy independent and is equal to $m/T_R\simeq 10^{10}$ in natural units. Since the analyzed galaxies are far away in the sky, we conclude that DM is a thermal relic, and $T_R$ in the above ratio can be expressed in terms of the temperature of the cosmic microwave background (CMB) at the time of DM decoupling. This result is used to study possible cosmological scenarios. We show that observations are at odds with (1) non-thermal DM, (2) hot DM, and (3) collision-less cold DM. Our findings are in favor of a warm DM with a mass of $\sim 1\,$MeV.
A. Borzou
Fri, 19 Feb 21
46/64
Comments: 7 pages, 7 figures
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