We report the discovery of two quasars at a redshift of $z$ = 6.05, in the process of merging. They were serendipitously discovered from the deep multi-band imaging data collected by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. The quasars, HSC $J$121503.42$-$014858.7 (C1) and HSC $J$121503.55$-$014859.3 (C2), both have luminous ($>$10$^{43}$ erg s$^{-1}$) Ly$α$ emission with a clear broad component (full width at half maximum $>$1000 km s$^{-1}$). The rest-frame ultraviolet (UV) absolute magnitudes are $M_{1450} = -23.106 \pm 0.017$ (C1) and $-22.662 \pm 0.024$ (C2). Our crude estimates of the black hole masses provide $\log (M_{\rm BH}/M_\odot) = 8.1 \pm 0.3$ in both sources. The two quasars are separated by 12 kpc in projected proper distance, bridged by a structure in the rest-UV light suggesting that they are undergoing a merger. This pair is one of the most distant merging quasars reported to date, providing crucial insight into galaxy and black hole build-up in the hierarchical structure formation scenario. A companion paper will present the gas and dust properties captured by Atacama Large Millimeter/submillimeter Array observations, which provide additional evidence for and detailed measurements of the merger and also demonstrate that the two sources are not gravitationally-lensed images of a single quasar.
The Cosmic Owl: Twin Active Collisional Ring Galaxies with Starburst Merging Front at $z=1.14$
Tsinghua University（清华大学）；National Radio Astronomy Observatory（国家射电天文台）；The University of Tokyo（东京大学）；Kavli Institute for the Physics and Mathematics of the Universe (WPI)（宇宙物理与数学研究 Kavli 研究所（WPI））；Center for Data-Driven Discovery, Kavli IPMU (WPI), UTIAS（数据驱动发现中心，Kavli IPMU（WPI），UTIAS）；Aix Marseille Univ.（艾克斯马赛大学）；CNRS（法国国家科学研究中心）；CNES（法国国家空间研究中心）；LAM（拉格朗日天体物理学实验室）；European Southern Observatory（欧洲南方天文台）
A cosmic collision in the making: JWST/NIRISS reveals a merging and maturing protocluster core at z~3 around a red quasar
Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut（海德堡大学天文学中心，天文计算研究所）；Space Telescope Science Institute（太空望远镜科学研究所）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Department of Physics, Rhodes College（罗德学院物理系）；Department of Physics and Astronomy, Bloomberg Center, Johns Hopkins University（约翰斯·霍普金斯大学彭博中心物理与天文学系）；Institute for Advanced Study（高等研究院）；Department of Astronomy and Joint Space-Science Institute, University of Maryland, College Park（马里兰大学帕克分校天文学系及联合空间科学研究所）；Departamento de Astronomia, Instituto de Física, Universidade Federal do Rio Grande do Sul（南里奥格兰德联邦大学物理研究所天文学系）
Accretion-modified Stars in Accretion Disks of Active Galactic Nuclei: Gravitational Wave Bursts and Electromagnetic Counterparts from Merging Stellar Black Hole Binaries
Growth of Supermassive Black Hole Seeds in ETG Star-Forming Progenitors: Multiple Merging of Stellar Compact Remnants via Gaseous Dynamical Friction and Gravitational Wave Emission
