The role of the elaphrocentre in low surface brightness galaxy formation Article - 2021

Marius Peper, Boudewijn F. Roukema

Marius Peper, Boudewijn F. Roukema, « The role of the elaphrocentre in low surface brightness galaxy formation  », Mon.Not.Roy.Astron.Soc., 2021

Abstract

The formation mechanisms of giant low surface brightness galaxies (LSBGs), with high masses and low star formation rates, remain unclear. 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 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 LSBG formation : while void galaxies are of lower mass, 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 LSBGs forming in voids.

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