Abstract
ABSTRACT 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 disc 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 disc 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.
Highlights
The role of the void environment in galaxy formation is worth exploring
This fraction of galaxies identified as void galaxies is larger than the 7% estimated by Pan et al (2012)
We have presented a complete, ab initio, reproducible galaxy formation pipeline starting from a standard post–recombination-epoch spectrum of initial perturbations, aiming to identify key factors in void galaxy formation that might contribute to the formation of giant low surface brightness galaxies in voids (Sect. 2.1)
Summary
A particular case of interest is that of giant low surface brightness galaxies (LSBGs). Hoffman, Silk & Wyse (1992) presented a peaks-in-peaks structureformation calculation arguing that voids are likely to play a major role in the formation of giant low surface brightness galaxies. We numerically investigate the role of voids in galaxy formation, with a particular emphasis of how voids may provide some of the characteristics leading to LSBG formation, by developing a reproducible pipeline that combines and builds on existing tools, which have developed considerably over the intervening three decades. It has long been known that a high volume fraction of the Universe consists of large underdense regions Since the fraction of volume occupied by voids may be as high as 80% (for theoretical estimates, see e.g. Colberg et al 2008; Cautun et al 2015), they are suspected to play a key role in relation to dark energy (e.g. Buchert et al 2016)
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