Invited Presentation

First Results of High-redshift Low-Luminosity Quasar Studies with JWST

Author(s): Masafusa Onoue (KIAA / Kavli IPMU)

Presenter: Masafusa Onoue (Peking University KIAA / Kavli IPMU)

The existence of billion-solar-mass black holes in the early universe has put a stringent constraint on the early growth history of supermassive black holes (SMBHs) and its relation to host galaxies. JWST is expected to be a game changer on both fronts, allowing us for the detection of low-luminosity quasars at high redshift as well as starlight of host galaxies. In this talk, I will show several ongoing JWST projects to characterize the representative population of SMBHs in the early universe. First, with the first imaging data from the Cosmic Evolution Early Release Science Survey (CEERS), we found one z>5 AGN candidate based on its characteristic photometric SED and its compact morphology. This source, named CEERS-AGN-z5-1, was later spectroscopically confirmed to be a broad-line AGN at z=5.24 by the ongoing NIRSpec/MSA spectroscopic follow-up campaign of the CEERS team. The inferred virial BH mass based on its broad H-alpha emission is M_BH = (1.3 x 0.4) x 10^7 Msun, which is approximately 2 dex lower-mass than that of a typical quasar known at z>5. With a few more sources that are under analysis, this early result demonstrates the capability of JWST for high-redshift AGN surveys. Another ongoing program led by the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) collaboration has recently reported the first detection of starlight from two low-luminosity quasars at z>6. They detected extended emission in NIRCam F356W and F150W images behind the central quasars, based on a 2D image-modeling technique to subtract the glaring nuclear emission. NIRSpec Fixed-Slit spectroscopy of the same sources reveals many rest-optical emission lines from the central quasars including broad Balmer lines and [OIII] 4960,5008 doublet. Combination of the stellar mass estimates from NIRCam and the H-beta-based virial BH estimates from NIRSpec suggests that these two quasars host “overmassive” SMBHs with respect to the local relation.