Average peak brightness temperature from CH₃CN J = 12 − 11 K transitions 2 to 4. The blue and red regions in (a) indicate where the properties in Section 4.2 are estimated and roughly follow the continuum 5σ level. Gray contours show the continuum emission from the combined data at the same levels as in Figure 1 but with σ _rms = 54 μJy beam⁻¹, and the green triangles indicate the continuum peaks. The beam size ellipse is shown in the lower left corner.