Speaker
Description
Using K giants selected from DESI Year-3 Milky Way (MW) Survey, we measure the shape, orientation, radial density profile, and spatial anisotropies in the density profile of the MW stellar halo at 8~kpc$<r_\mathrm{GC}<200$~kpc. With forward modelling, we identify a triaxial stellar halo (axis ratio $10:8:7$), $43\degree$ tilted from the disc, showing two break radii at $\sim16$~kpc and $\sim76$~kpc, which we suggest are associated with GSE and LMC, respectively. We explore the model dependency on [Fe/H] and find that more metal-poor halo stars are more radially extended. We find that the shape and orientation of the stellar halo depend on distance: the inner stellar halo ($<30$ kpc) is oblate and aligned with the Galactic disc, whereas the outer stellar halo becomes prolate and perpendicular to the disc, consistent with the Vast Polar Structures. The anisotropic density distribution of the stellar halo is also measured, with successful identification of the HAC-N/-S and VOD overdensities. A break radius at 15~kpc is found for VOD and at 30~kpc for HAC-N/-S, consistent with GSE. We identify the LMC transient density wake with a break radius at 60~kpc in the Pisces overdensity. We also find new observational evidence of the LMC collective density wake, by showing a break radius at $\sim$100~kpc in the northern Galactic cap with a clear density peak at 90~kpc. The density in the northern cap is about 4.5 times denser than that in the south between $r_\mathrm{GC}\sim50$kpc and $r_\mathrm{GC}\sim100$kpc.