Recently a new particle physics model called Bound Dark Matter ( BDM ) has been proposed [ 1 ] in which dark matter ( DM ) particles are massless above a threshold energy ( E _ { c } ) and acquire mass below it due to nonperturbative methods .
Therefore , the BDM model describes DM particles which are relativistic , hot dark matter ( HDM ) in the inner regions of galaxies and describes nonrelativistic , cold dark matter ( CDM ) where halo density is below \rho _ { c } \equiv E _ { c } ^ { 4 } .
To realize this idea in galaxies we use a particular DM cored profile that contains three parameters : a typical scale length ( r _ { s } ) and density ( \rho _ { 0 } ) of the halo , and a core radius ( r _ { c } ) stemming from the relativistic nature of the BDM model .
We test this model by fitting rotation curves of seventeen Low Surface Brightness ( LSB ) galaxies from The HI Nearby Galaxy Survey ( THINGS ) .
Since the energy E _ { c } 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 r _ { s } ,r _ { c } ,E _ { c } are constrained , leaving only two free parameters .
The high spatial and velocity resolution of this sample allows to derive the model parameters through the numerical implementation of the \chi ^ { 2 } -goodness-of-fit test to the mass models .
We compare the fittings with those of Navarro-Frenk-White ( NFW ) , Burkert , and Pseudo-Isothermal ( ISO ) profiles .
Through the results we conclude that the BDM profile fits better , or equally well , than NFW , Burkert , and ISO profiles and agree with previous results implying that cored profiles are preferred over the N-body motivated cuspy profiles .
We also compute 2D likelihoods of the BDM parameters r _ { c } and E _ { c } for the different galaxies and matter contents , and find an average galaxy core radius r _ { c } = 300 pc and a transition energy between hot and cold dark matter at E _ { c } = 0.11 ^ { +0.21 } _ { -0.07 } { eV } when the DM halo is the only component , therefore the maximum dark matter contribution in galaxies .
In a more realistic analysis , as in Kroupa mass model , we obtain a core r _ { c } = 1.48 kpc , and energy E _ { c } = 0.06 ^ { +0.07 } _ { -0.03 } { eV } .