ALMA continuum map of Sgr B2(N) at 85 GHz. The black contour lines show the flux density levels at 3σ, 6σ, 12σ, and 24σ and the dotted lines indicate −3σ, where σ is the rms noise level of 5.4 mJy beam⁻¹. The white crosses denote the positions of the two main hot cores, Sgr B2(N1) and Sgr B2(N2). The black cross, located between the white ones, indicates the phase centre. The green crosses show peaks of continuum emission selected for our absorption study. They label the ultra-compact H II region K4, two peaks in the shell of the H II region K6 and one peak in the shell of the H II region K5 (Gaume et al. 1995). The green ellipse in the lower left corner shows the size of the synthesized beam of ~1. ′′6 (see Table 1).