Crosscuts along the planes XY, XZ, and YZ in the L19 3D dust extinction map, with the same conventions as in Fig. 1. The (common) gray scale shows , with in units of magnitude per parsec. The red and green lines mark the inner and outer surfaces of the LB shell (r_inner and r_outer, respectively), as extracted from the L19 map (Sect. 2.2.1). The black dotted, dashed, and solid lines trace our models of the inner surface (r_LB), as obtained through a spherical harmonic expansion up to l_max = 2, 6 and 10, respectively (Sect. 2.2.2).