Spectral energy distribution of M 2-9. Left: total (dust and free-free) mm continuum fluxes measured with ALMA in different SPWs (filled circles, Table 1). The global fit (S_ν ∝ v^0·92±0·1) is depicted with a solid line. The dashed line represents a fit to the free-free emission in the radio continuum, using the 4.9–43 GHz datasets from de la Fuente et al. (2022), which also reproduces our mm continuum fluxes after subtracting the contribution from a compact ~260 K dust component (shown in the right panel) – open squares. Right: SED of M 2-9 from the near-IR to the radio domain as in Sánchez Contreras et al. (2017) and including our ALMA mm continuum flux measurements (cyan). Radio continuum flux measurements at 4.9–43 GHz from the ionized wind/core as reported by de la Fuente et al. (2022) are indicated with pink circles. Mid-IR photometry of the compact, warm (~260 K) dust disk at the core of M 2-9 is shown with red triangles in the 8-20 µm range. Fits to the free- free and dust thermal emission are depicted, with the nearly flat continuum from the ionized bipolar lobes and the free-free emission from the ionized wind/core (S_v ∝ ν⁰·⁸⁹) shown as a dotted-dashed and a dashed line, respectively. Several modified black-body components are also plotted, including a ~95 K component originating from dust located in the extended bipolar lobes, and filtered in our ALMA maps, (dotted line) and a ~260 K component arising from dust in a compact disk at the center of M 2-9 (red line). For completeness, a hot ~600 K dust component, which is necessary to explain the optical/NIR photometry, is also represented. The blue solid line represents the combined fits for the free-free and dust emission components. The red triangles at 1 mm and 3 mm represent the residual dust emission of M 2-9 after subtracting a S_v ∝ ν^0.89 free-free emission component from the ionized wind/core.