The role of the elaphrocentre in void galaxy formation
  Voids may affect galaxy formation via weakening mass infall or increasing
disk sizes, which could potentially play a role in the formation of giant low
surface brightness galaxies (LSBGs). If a dark matter halo forms at the
potential hill corresponding to a void of the cosmic web, which we denote the
'elaphrocentre' in contrast to a barycentre, then the elaphrocentre should
weaken the infall rate to the halo when compared to infall rates towards
barycentres. We investigate this hypothesis numerically. We present a complete
software pipeline to simulate galaxy formation, starting from a power spectrum
of initial perturbations and an N-body simulation through to
merger-history-tree based mass infall histories. The pipeline is built from
well-established, free-licensed cosmological software packages, and aims at
highly portable long-term reproducibility. We find that the elaphrocentric
accelerations tending to oppose mass infall are modest. We do not find evidence
of location in a void or elaphrocentric position weakening mass infall towards
a galaxy. However, we find indirect evidence of voids influencing galaxy
formation: while void galaxies are of lower mass compared to galaxies in high
density environments, their spin parameters are typically higher. For a fixed
mass, the implied disk scale length would be greater. Tangential accelerations
in voids are found to be high and might significantly contribute to the higher
spin parameters. We find significantly later formation epochs for void
galaxies; this should give lower matter densities and may imply lower surface
densities of disk galaxies. Thus, void galaxies have higher spin parameters and
later formation epochs; both are factors that may increase the probability of
forming LSBGs in voids.
