Observed spectral energy distribution of RX J1131-1231 with the multi-wavelength photometry of the lensed images, not corrected for the gravitational lensing magnification (blue points with error bars). From left to right: Herschel 250, 350 and 500 μm (this work), CARMA 1.4 mm continuum (Leung et al. 2017), ALMA 2.1 mm continuum (this work), PdBI 2.2 mm continuum (Leung et al. 2017) and the VLA 4.86 GHz (this work). The rest-frame best-fit modified black body spectrum for the heated dust is shown in grey, with an effective dust temperature K and dust emissivity index .