ALMA continuum emission maps of M 2-9 at 232.9 GHz (left) and 95.4 GHz (right). The top row displays the images after image restoration using the nominal beam size at each frequency (Sect. 3). The bottom row presents the images with a circular restoring beam of 0.″04 at both frequencies, allowing for an optimal comparison between the two. The level contours are (3σ)×1.5⁽ⁱ⁻¹⁾ Jy beam⁻¹, i =1,2,3… The central cross marks the 3 mm continuum surface brightness peak at coordinates J2000 RA=17^h05^m37^s.9668 and Dec=−10º08′32.″65 (J2000). The yellow arcs, centered at the small yellow cross, represent the broad-waist structure, plausibly a dust disk, detected at 1 mm but not at 3 mm.