torquing in the early universe [@peebles69; @dorosh70; @white84], and is later modified and shaped by the merging and accretion of substructures (e.g. @frenk85 [@catelan96; @bullock01; @gardner01; @vitvitska02; @peirani04; @donghia07]). The acquisition and distribution of angular momenta in haloes is intimately linked to the evolution of the galaxies at their centres. Indeed, the relationship between halo spin and disc/baryonic spin is a fundamental topic in galaxy formation, and has been studied extensively in the literature (e.g. @vandenbosch02 [@sharma05; @zavala08; @bett10; @deason11b; @teklu15; @zavala16]).

Initially, the angular momentum of the galaxy and the dark matter halo can be very well aligned. However, material is continually accreted onto the outer parts of the halo, which can alter its net angular momentum. Hence, while the galaxy and the halo often have aligned angular momentum vectors near their centers, they can be significantly misaligned at larger radii (e.g. @bett10 [@deason11b; @gomez17]). Furthermore, major mergers can cause drastic “spin flips” in both the dark matter angular momenta and the central baryonic component [@bett12; @padilla14].

It is clear that the net spin of haloes is critically linked to their merger histories, and thus their *stellar haloes* could provide an important segue between the angular momenta of the 