High Star Formation Rates of Low Eddington Ratio Quasars at z ≳ 6

Recent simulation studies suggest that the supermassive black hole (SMBH) growth in the early universe may precede prolonged intense star formation within its host galaxy, rather than quasars appearing after the obscured dusty star formation phase. If so, high-redshift quasars with low Eddington ratios (lambda(Edd)) would be found in actively star-forming hosts with a star formation rate (SFR) of >100 M-circle dot yr(-1). We present the submillimeter observations of IMS J2204+0112, a faint quasar with a quasar bolometric luminosity of L-bol = 4.2 x 10(12) L-circle dot and a low lambda(Edd) of only 0.1 at z similar to 6, carried out with the Atacama Large Millimeter/submillimeter Array (ALMA). From its submillimeter fluxes, we measure the rest-frame far-infrared (FIR) luminosity of L-FIR = (3-4) x 10(12) L-circle dot. Interestingly, the derived host galaxy's SFR is similar to 500-700 M-circle dot yr(-1), an order of magnitude higher than those of the L-bol-matched z greater than or similar to 6 quasars with high lEdd. Similar FIR excesses are also found for five z greater than or similar to 6 low-lambda(Edd) quasars (lambda(Edd) < 0.2) in the literature. We show that the overall SFR, M-BH, and lambda(Edd) distributions of these and other submillimeter-detected quasars at z greater than or similar to 6 can be explained with the evolutionary track of high-redshift quasars in a simulation study, where low lambda(Edd) and high SFR quasars are expected at the end of the SMBH growth. This suggests that the nuclear activities of the low lambda(Edd), high L-FIR quasars are on the brink of being turned off, while their host galaxies continue to form the bulk of their stars at SFR > 100 M-circle dot yr(-1).