Dark Matter Phase Transition Constrained at O(0.1) eV with LSB Rotation
  Curves
  In order to unravel the nature of the dark matter (DM) we have proposed a
particle-physics motivated model called Bound Dark Matter (BDM) that consist in
DM massless particles above a threshold energy Ec that acquire mass below it
due to nonperturbative methods. Therefore, the BDM model describes DM particles
which are relativistic, hot dark matter (HDM) in the denser (inner) regions of
galaxies and describes nonrelativistic, cold dark matter (CDM) where halo
density is below rho_c = Ec^4. We test this model by fitting rotation curves
from Low Surface Brightness (LSB) galaxies from The HI Nearby Galaxy Survey
(THINGS). We use a particular DM cored profile that contains three parameters:
a typical scale length (rs) and density (rho_0) of the halo, and a core radius
(rc) stemming from the relativistic nature of the BDM model. Since the energy
Ec parameterizes the phase transition due to the underlying particle physics
model, it is independent on the details of galaxy and/or structure formation
and therefore the DM profile parameters rs, rc, Ec are constrained, leaving
only two free parameters. Through the results we agree with previous ones
implying that cored profiles are preferred over the N-body motivated cuspy
profiles. We also compute 2D likelihoods of the BDM parameters rc and Ec for
the different galaxies and matter contents, and find an average galaxy core
radius rc = 1.48kpc and a transition energy between hot and cold dark matter at
Ec = 0.06 eV. The phase transition scale Ec is a new fundamental scale for our
DM model well motivated theoretical origin from gauge group dynamics.
