Density shape and profile of the stellar halo traced by the BHB sample. The top panel shows the variation in q with increasing r for all BHB stars (blue points) and the subsample (orange points). To better distinguish the results of the two samples, a constant of 0.2 is added to q of the subsample. The stellar halo is largely vertically flattened in the inner part and transformed into a nearly spherical shape at the outer radii. The bottom panel shows the relationship between the radial stellar density log(ν) and the flattened radius r. Assuming a variable flattening, the radial density profile of the stellar halo derived from all BHB stars (blue points) can be well described by a SPL with an index α = −4.80 ± 0.06, and for the subsample (orange points, a constant of 0.5 is added to log(ν)) the best result is α = −4.65 ± 0.04.