@article{3a01f40f32be4569b687e7317c872f31,
title = "Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). III. Star formation properties of the host galaxies at z ∼ 6 studied with ALMA",
abstract = "We present our ALMA Cycle 4 measurements of the [C II] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity (M1450 > -25) quasars at z ≳ 6 discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [C II] line and FIR continuum luminosities lie in the ranges L[C II] = (3.8-10.2) × 108 L· and LFIR = (1.2-2.0) × 1011 L·, which are at least one order of magnitude smaller than those of optically-luminous quasars at z ≳ 6. We estimate the star formation rates (SFRs) of our targets as ≲ 23-40 M· yr-1. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically-luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The L[C II]/LFIR ratios of the hosts, ≲ (2.2- 8.7) × 10-3, are fully consistent with local star-forming galaxies. Using the [C II] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as ≲ (1.4-8.2) × 1010 M·. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at z ∼ 6, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically-luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of most of the low-luminosity quasars, including the HSC ones, are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole host galaxy evolution.",
keywords = "galaxies: ISM, galaxies: high-redshift, galaxies: quasars, galaxies: starburst, quasars: general",
author = "Takuma Izumi and Masafusa Onoue and Hikari Shirakata and Tohru Nagao and Kotaro Kohno and Yoshiki Matsuoka and Masatoshi Imanishi and Strauss, {Michael A.} and Nobunari Kashikawa and Andreas Schulze and Silverman, {John D.} and Seiji Fujimoto and Yuichi Harikane and Yoshiki Toba and Hideki Umehata and Kouichiro Nakanishi and Greene, {Jenny E.} and Yoichi Tamura and Akio Taniguchi and Yuki Yamaguchi and Tomotsugu Goto and Yasuhiro Hashimoto and Soh Ikarashi and Daisuke Iono and Kazushi Iwasawa and Lee, {Chien Hsiu} and Ryu Makiya and Takeo Minezaki and Tang, {Ji Jia}",
note = "Funding Information: The Pan-STARRS1 Surveys (PS1) have been made possible through contributions of the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, Queen{\textquoteright}s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under Grant No. AST-1238877, the University of Maryland, and Eotvos Lorand University (ELTE). Funding Information: The Hyper Suprime-Cam (HSC) collaboration includes the astronomical communities of Japan and Taiwan, and Princeton University. The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, the High Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University. Funding Information: T.I., M.O., K.K, N.K., H.U., R.M., and T.N. are supported by JSPS KAKENHI grant numbers 17K14247 (T.I.), 15J02115 (M.O.), 17H06130 (K.K.), 15H03645 (N.K.), 17K14252 (H.U.), 15H05896 (R.M.), 16H01101, 16H03958, and 17H01114 (T.N.), respectively. H.S. has been supported by the Sasakawa Scientific Research Grant from the Japan Science Society (29-214). T.I. is supported by the ALMA Japan Research Grant of NAOJ Chile Observatory, NAOJ-ALMA-175. Publisher Copyright: {\textcopyright} 2018 The Author(s).",
year = "2018",
month = jun,
day = "1",
doi = "10.1093/pasj/psy026",
language = "English (US)",
volume = "70",
journal = "Publication of the Astronomical Society of Japan",
issn = "0004-6264",
publisher = "Astronomical Society of Japan",
number = "3",
}