Estimated stellar halo mass between 40 kpc and 70 kpc as a function of the truncation strengths. Three panels represent results from the analysis of the entire region (a), the east (b) and the west (c) sides of M 101. Disk models with a truncation starting at 35 kpc, 40 kpc, and 45 kpc are also considered as marked by pentagons, squared, and triangles, respectively. The upper limit of the estimated halo masses, M_{halo, 40−70} = 5 × 10⁷ M_⊙, is indicated by a dashed line in each panel.