Constraining galactic structures of mirror dark matter
  The simplest model of mirror sector dark matter maintains exact mirror
symmetry, but has a baryon abundance $\Omega_{b'} = \beta \Omega_b$ and a
suppressed temperature $T' = x T$ in the mirror sector; hence it depends only
on two parameters, $\beta,x$. For sufficiently small $x$, early cosmological
observables may not constrain mirror baryons from constituting all of the dark
matter despite their strong self-interactions, depending on the unknown details
of structure formation in the hidden sector. Here we close this loophole by
simulating mirror structure formation, mapping out the allowed regions of
parameter space using cosmological and astronomical data. We find that the
Milky Way disk surface density and bulge mass constrain $\Omega_{b'}\lesssim
0.3 \Omega_{b}$ at the highest $T'$ allowed by BBN and CMB ($T'=0.5 T$), or
$\Omega_{b'}\lesssim 0.8 \Omega_{b}$ at lower values of $T'$. We also briefly
discuss the realization of the necessary temperature asymmetry between the SM
and the mirror sector in our model with unbroken mirror symmetry.
