Upper panel: color image and white contours represent the 1.3 mm high-resolution continuum map of the W51 IRS2 region. Contour levels are [−5, −3, 3, 5, 10, 20, 40, 80, 120, 160] × σ (σ = 0.15 mJy beam⁻¹). Red contours correspond to the 3 mm continuum map, and they are [−3, 3, 5, 10, 20, 40, 80, 120, 160, 200, 300, 400, 500] × σ (σ = 0.08 mJy ⁻¹). The red and white ellipses in the bottom-right corner indicate the synthesized beams of the 3 and 1.3 mm high-resolution continuum maps, respectively. Bottom panel: color image represents the spectral index map that was derived from the 1.3 and 3 mm high-resolution continuum maps. The black contours are the 1.3 mm high-resolution continuum, and the contour levels are the same as in the upper panel.