Study of Dark-Matter Admixed Neutron Stars using the Equation of State
  from the Rotational Curves of Galaxies
  In this work, we employ the dark matter equations of state (DMEOSs) obtained
from the rotational curves of galaxies as well as the fermionic DMEOS with m =
1.0 GeV to study the structure of darkmatter admixed neutron stars (DMANSs).
Applying the equation of state in the Skyrme framework for the neutron matter
(NM), we calculate the mass-radius relation for different DMANSs with various
DMEOSs and central pressure of dark matter (DM) to NM ratios. Our results show
that for some DMEOSs, the mass-radius relations are in agreement with new
observations, e.g. EXO 1745-248, 4U 1608-52, and 4U 1820-30, which are
inconsistent with the normal neutron stars. We conclude that both DMEOSs and
central pressure ratios of DM to NM affect the slope of the mass-radius
relation of DMANSs. This is because of the interaction between DM and NM, which
leads to gravitationally or self-bound DMANSs. We study the radius of the NM
sphere as well as the radius of the DM halo for different DMANSs. The results
confirm that, in some cases, a NM sphere with a small radius is surrounded by a
halo of DM with a larger radius. Our calculations verify that, due to the
different degrees of DM domination in DMANSs, with a value of the visible
radius of a star two possible DMANSs with different masses can be exist. The
gravitational redshift is also calculated for DMANSs with different DMEOSs and
central pressure ratios. The results explain that the existence of DM in a
DMANS leads to higher values of gravitational redshift of the star.
