Top panel: FIR to radio SED of GH500.30 (open squares). The black curve shows the best-fit SED among all 105 CE01 templates. The best-fits with Mrk 231, Arp 220 and M82 SED are shown in red, green and blue curves, respectively. The fill squares are observed Spitzer/IRAC fluxes. Bottom panel: χ²vs. redshift. The black curve represents the results from the best-fit CE01 SED at each redshift, and the color-coded curves are for the Mrk 231, Arp 220 and M82 SED. The horizontal dashed line shows the 90% confidence interval for the redshift. The lower panel at the bottom shows the IR luminosities from CE01 templates that allow for the minimum χ² at each redshift. The vertical gray curve represents the best-fit redshift (z = 4.19) from the optical-to-NIR SED.