An Optically Faint Quasar Survey at z ∼ 5 in the CFHTLS Wide Field: Estimates of the Black Hole Masses and Eddington Ratios

We present the result of our spectroscopic follow-up observation for faint quasar candidates at z similar to 5 in part of the Canada-France-Hawaii Telescope Legacy Survey wide field. We select nine photometric candidates and identify three z similar to 5 faint quasars, one z similar to 4 faint quasar, and a late-type star. Since two faint quasar spectra show the C. IV emission line without suffering from a heavy atmospheric absorption, we estimate their black hole masses (M-BH) and Eddington ratios (L/L-Edd). The inferred log M-BH are 9.04 +/- 0.14 and 8.53 +/- 0.20, respectively. In addition, the inferred log(L/L-Edd) are - 1.00 +/- 0.15 and -0.42 +/- 0.22, respectively. If we adopt that L/L-Edd constant or proportional to(1 + z)(2), the seed black hole masses (M-seed) of our z similar to 5 faint quasars are expected to be > 10(5) M-circle dot in most cases. We also compare the observational results with a mass accretion model, where angular momentum is lost due to supernova explosions. Accordingly, M-BH of the z similar to 5 faint quasars in our sample can be explained even if M-seed is similar to 10(3) M-circle dot. Since z similar to 6 luminous qusars and our z similar to 5 faint quasars are not on the same evolutionary track, z similar to 6 luminous quasars and our z similar to 5 quasars are not the same populations but different populations, due to the difference of a period of the mass supply from host galaxies. Furthermore, we confirm that one can explain M-BH of z similar to 6 luminous quasars and our z similar to 5 faint quasars even if their seed black holes are formed at z similar to 7.