Virialization of high redshift dark matter haloes
  We present results of a study of the virial state of high redshift dark
matter haloes in an N-body simulation. We find that the majority of collapsed,
bound haloes are not virialized at any redshift slice in our study ($z=15-6$)
and have excess kinetic energy. At these redshifts, merging is still rampant
and the haloes cannot strictly be treated as isolated systems. To assess if
this excess kinetic energy arises from the environment, we include the surface
pressure term in the virial equation explicitly and relax the assumption that
the density at the halo boundary is zero. Upon inclusion of the surface term,
we find that the haloes are much closer to virialization, however, they still
have some excess kinetic energy. We report trends of the virial ratio including
the extra surface term with three key halo properties: spin, environment, and
concentration. We find that haloes with closer neighbors depart more from
virialization, and that haloes with larger spin parameters do as well. We
conclude that except at the lowest masses ($M < 10^6 \Msun$), dark matter
haloes at high redshift are not fully virialized. This finding has interesting
implications for galaxy formation at these high redshifts, as the excess
kinetic energy will impact the subsequent collapse of baryons and the formation
of the first disks and/or baryonic structures.
