We report observations of the low-luminosity z = 5.50 quasar RD J030117+002025 ( RD0301 hereafter ) at 250 GHz ( 1.20 mm ) using the Max-Planck Millimeter Bolometer ( MAMBO ) array at the IRAM 30-meter telescope .
The quasar was detected with a 1.2 mm flux density of 0.87 \pm 0.20 mJy .
The lack of detectable 1.4 GHz radio emission indicates that the millimeter emission is of thermal nature , making RD0301 the most distant dust-emission source known .
When matching a 50 K grey body thermal far-infrared ( FIR ) spectrum to the observed millimeter flux we imply a FIR luminosity \approx 4 \times 10 ^ { 12 } L _ { \odot } , which is comparable to the quasar ’ s optical luminosity .
If the FIR luminosity arises from massive star formation , the implied star formation rate would be \sim 600 M _ { \odot } yr ^ { -1 } , comparable to that of the starburst galaxies which dominate the average star formation and FIR emission in the early Universe .
The FIR luminosity of RD0301 is close to the average of that found in optically far more luminous high-redshift quasars .
The comparably high millimeter to optical brightness ratio of RD0301 is further evidence for that there is no strong correlation between the optical and millimeter brightness of high-redshift quasars , supporting the idea that in high-redshift quasars the dust is not heated by the AGN , but by starbursts .