Spin Flips: Variation in the Orientation of Dark Matter Halos over their Merger Histories

TL;DR

This paper investigates how dark matter halos and galaxy spins can change orientation over time, exploring the potential impact of non-merger events like fly-bys on galaxy formation.

Contribution

It introduces a preliminary analysis of spin orientation variations, highlighting non-merger events as possible influences on galaxy bulge formation.

Findings

Dark matter halos exhibit spin orientation changes over their merger histories.

Non-merger events may significantly perturb galaxy and halo spins.

Spin flips could contribute to bulge formation without major mergers.

Abstract

Semi-analytic models of galaxy formation typically form the spheroidal components of galaxies ("bulges"), solely through galactic major mergers. However, it is possible that non-merger events (e.g. a "fly-by" by a smaller halo) can perturb a galaxy--halo system sufficiently to form a bulge. We present a preliminary investigation into the frequency of major changes in halo and galaxy spin direction, which could be signatures of such events.