Rapid evolution and transformation into quiescence?: ALMA view on z > 6 low-luminosity quasars

We present ALMA [CII] line and far-infrared (FIR) continuum observations of seven z > 6 low-luminosity quasars (M₁₄₅₀ > -25 mag) discovered by our on-going Subaru Hyper Suprime-Cam survey. The [CII] line was detected in all targets with luminosities of ∼(2-10) × 10⁸ L_⊙, about one order of magnitude smaller than optically luminous quasars. Also found was a wide scatter of FIR continuum luminosity, ranging from L_FIR < 10¹¹L_⊙ to ∼2 × 10¹²L_⊙. With the [CII]-based dynamical mass, we suggest that a significant fraction of low-luminosity quasars are located on or even below the local Magorrian relation, particularly at the massive end of the galaxy mass distribution. This is a clear contrast to the previous finding that luminous quasars tend to have overmassive black holes relative to the relation. Our result is expected to show a less-biased nature of the early co-evolution of black holes and their host galaxies.