82 GHz (top panel: 3.65 mm) and 97 GHz (bottom panel: 3.1 mm) continuum emission as observed with NOEMA toward L1521F. The first contour and the level step are at 3σ (where 1σ = 1.6 × 10⁻⁵ and 1.5 × 10⁻⁵ Jy beam⁻¹ at 82 and 97 GHz, respectively). The white triangles indicate the positions of the MMS-1, MMS-2, and MMS-3 sources (see Sect. 1). Synthesized beams are shown in the bottom left corner of the panels.