Dust continuum emission components. Left: Visibity amplitude (Jy) vs. the antenna spacing in the uv plane (m) of the continuum emission at 261.3 GHz (self-calibrated data) in black and model fit of a point source (flux= 9.1 ±0.1 mJy) in red. Middle: Residuals of the continuum visibility amplitude after subtraction of the point source model in the top panel in black and new model fit of the residuals adopting a uniform elliptical disc model (flux= 25.6±0.2mJy) in red. See details of the model fit parameters of both (point and elliptical disc) components in Sect. 3. In both panels, the uv-data are averaged over a time interval of 4500 s (approximately the total on-source integration time in each observing block) to reduce the noise in these plots. Right: Cleaned map of the residual after subtracting the point source and extended disk model to the observed 261 GHz-continuum map shown in Fig. 1 (left), using the same contour level step.