The optical-UV continuum of quasars is broadly consistent with the emission from a geometrically thin optically thick accretion disk (AD). The AD produces the ionizing continuum which powers the broad and narrow emission lines. The maximum AD effective temperature is given by Teff=fmax(Mdot/M^2)^1/4, where M is the black hole mass, Mdot the accretion rate, and fmax is set by the black hole spin a_*. For a low enough value of Mdot/M^2 the AD may become too cold to produce ionizing photons. Such an object will form a lineless quasar. This occurs for a local blackbody (BB) AD with a luminosity Lopt=10^46 erg/s for M>3.6E9 Msun, when a_*=0, and for M>1.4E10 Msun, when a_*=0.998. Using the AD based Mdot, derived from M and Lopt, and the reverberation based M, derived from Lopt and the Hbeta FWHM, v, gives Teff \propto Lopt^-0.13v^-1.45. Thus, Teff is mostly set by v. Quasars with a local BB AD become lineless for v> 8,000 km/s, when a_*=0, and for v> 16,000 km/s, when a_*=0.998. Higher values of v are required if the AD is hotter than a local BB. The AD becoming non-ionizing may explain why line emitting quasars with v>10,000 km/s are rare. Weak low ionization lines may still be present if the X-ray continuum is luminous enough, and such objects may form a population of weak emission line quasars (WLQ). If correct, such WLQ should show a steeply falling SED at lambda<1000A. Such an SED was observed by Hryniewicz et al. in SDSS J094533.99+100950.1, a WLQ observed down to 570A, which is well modeled by a rather cold AD SED. UV spectroscopy of z~1-2 quasars is required to eliminate potential intervening Lyman limit absorption by the intergalactic medium (IGM), and to explore if the SEDs of lineless quasars and some additional WLQ are also well fit by a cold AD SED.
A Potential Link between Nuclear Winds and Cold Gas Outflows on Kiloparsec Scales in Reionization-Era Quasars
Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；Department of Astronomy, School of Physics, Peking University（北京大学物理学院天文学系）；Center for Astronomy and Astrophysics and Department of Physics, Fudan University（复旦大学天文与空间科学中心及物理系）；Department of Space, Earth, & Environment, Chalmers University of Technology（查尔姆斯理工大学空间、地球与环境系）；Department of Physics & Astronomy, University of California, Riverside（加州大学河滨分校物理与天文学系）；Department of Astronomy, University of Michigan（密歇根大学天文学系）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）
ALMA survey of a massive node of the Cosmic Web at $z\sim 3$. II. A dynamically cold and massive disk galaxy in the proximity of a hyperluminous quasar
One H2 molecule per ten million H-atoms reveals sub-pc scale cold overdensities at z~4
NRC Herzberg Astronomy and Astrophysics Research Centre（加拿大国家研究委员会赫茨伯格天文学和天体物理学研究中心）；INAF - Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）；IFPU - Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；National Institute for Nuclear Physics（国家核物理研究所）；Departamento de Astronomía, Universidad de Chile（智利大学天文学系）；LERMA, Observatoire de Paris, Université PSL, Sorbonne Université（巴黎天文台，PSL大学，索邦大学）；Laboratoire de Physique de l’Ecole Normale Supérieure, PSL, CNRS, SU, Université de Paris（巴黎高等师范学院物理实验室）
Sharpening quasar absorption lines with ESPRESSO: Temperature of warm gas at $z\sim2$, constraints on the Mg isotopic ratio, and structure of cold gas at $z\sim0.5$
Discovery of a Perseus-like cloud in the early Universe: HI-to-H2 transition, carbon monoxide and small dust grains at zabs=2.53 towards the quasar J0000+0048
