Central region of the SABOCA 350 μm map. The grayscale is in Jy/beam. The red contours show significance levels of  ± 2.5, 3.0and3.5σ (positive values as solid lines and negative values as dashed lines). SMM J0658 is detected at the center of this image at 3.6σ significance. The white circles indicate the positions of the three Spitzer images A, B and C (Gonzalez et al. 2009). The magenta circle has a diameter of 106, the FWHM of the SABOCA image; it is located at the position of an infrared-bright elliptical galaxy at z = 0.35 (Rex et al. 2010) which is not detected by SABOCA, as expected (the continuum from this galaxy is detected in the ATCA 7 mm observations and used to assess the astrometry of the CO(1–0) map, see Sect. 3.2.1). The yellow dashed lines correspond to the 3,6and9σ levels of the LABOCA 870 μm detection. The source was detected by Herschel (Rex et al. 2010): the cyan circle shows the size of the Herschel beam at 350 μm (FWHM of 25′′). The coordinates of the (0,0)-position are the same as those of the phase center of the ATCA observations, which are listed in Table 1.