It has been claimed that massive outflows driven by active galactic nuclei (AGN) during the transition from an obscured dusty quasar to a normal blue quasar are a key physical process driving the co-evolution of galaxies and supermassive black holes (SMBHs). Partially dust-obscured red quasars are thought to represent an intermediate phase of this transition, making it crucial to investigate this species along with various epochs.
Here, we report on our ALMA Cycle 7 observations of the red quasar HSC J120505.09−000027.9 (J1205−0000) at z = 6.72. This red quasar was initially identified through our deep Subaru Hyper Suprime-Cam (HSC) survey. Although it appears faint, it is intrinsically as luminous as -24.4 mag at rest-UV and hosts a massive black hole of 2.2 × 10^9 Msun. It is also known to be an N V and C IV BAL object, indicating the presence of nuclear outflows.
We successfully detected both the [CII] 158 μm line and the underlying rest-FIR continuum emission (resolution ~0.6", 1σ ~ 0.1 mJy/beam at dV = 75 km/s). The continuum is very bright, with an estimated luminosity of 3.5 × 10^12 Lsun (equivalent to a star formation rate of ~520 Msun/yr), suggesting that the host galaxy of this red quasar is indeed a starburst system. Furthermore, our observations do not conclusively confirm the presence of [CII] outflows. These results suggest that this red quasar may be positioned in the early phase of the galaxy merger-induced evolution model.