$N=4553$ BHB stars. We estimate distances to these stars using the $g-r$ colour and metallicity dependent relation derived by [@fermani13a]. Similarly to the RRL stars, we do not take into account the relatively small ($\sim 10\%$) distance uncertainties of the BHBs in our analysis. Our resulting BHB sample has 3D positions, 3D velocities and spectroscopic metallicity estimates.

K Giants
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Giant stars are often a useful probe of the stellar halo, owing to their bright absolute magnitudes ($M_r \sim 1$ to $-3$), and large numbers in wide-field spectroscopic surveys (e.g. @morrison00 [@xue14]). Moreover, giants are one of the most common tracers of *external* galaxy haloes (e.g. @gilbert06 [@monachesi16]). In contrast to BHB and RRL stars, giant stars populate all metallicities in old populations. Thus, they represent a less biased tracer of the stellar halo.

The drawback of using giant stars to trace the halo is that spectroscopic samples are required to limit contamination from dwarf stars, and the absolute magnitudes of giants are strongly dependent on colour and metallicity. Here, we use the spectroscopic sample of K giants compiled by [@xue14], who derive distance moduli for each star using a probabilistic framework based on colour and metallicity. A distance modulus 