Left: SED fits to the HST/ACS-WFC3 photometry of the images B and D (A is contaminated by a nearby source, C is in a noisy strip of the detector). The best fits give z = 6.3 ± 0.3. The inset shows the VLT/FORS spectrum of the B image with the Ly-α line clearly detected at z = 6.107 (Richard et al., in prep.). The x-axis of the inset corresponds to the observed wavelength in Å. Right: SED fits to the 870 μm northern peak taking into account the upper limits listed in the Table 1 and assuming z = 6.1 and μ = 10 (all the fluxes are corrected for magnification). The modified black-body SED with T_d = 30 K is shown in blue, it gives a FIR luminosity L_FIR = 5 × 10¹¹ L_⊙. The other templates come from the the Chary & Elbaz (2001) library (red), the Vega et al. (2008) library (green), the Michałowski et al. (2010a,b) library (cyan), and the Polletta et al. (2007) library (orange). The template in magenta corresponds to the SMM J2135-0102 model (Swinbank et al. 2010; Ivison et al. 2010).