948 citations · 3.4k across the 53 of their papers we have counts for
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Toward precise constraints on growth of massive black holes
Qingjuan Yu, Youjun Lu
Growth of massive black holes (MBHs) in galactic centers comes mainly from gas accretion during their QSO/AGN phases. In this paper we apply an extended Soltan argument, connecting…
Hypervelocity binary stars: smoking gun of massive binary black holes
Youjun Lu, Qingjuan Yu, D. N. C. Lin
The hypervelocity stars recently found in the Galactic halo are expelled from the Galactic center through interactions between binary stars and the central massive black hole or be…
On the origin of kinematic distribution of the sub-parsec young stars in the Galactic center
Qingjuan Yu, Youjun Lu, D. N. C. Lin
Within a half-parsec from the Galactic center (GC), there is a population of coeval young stars which appear to reside in a coherent disk. Surrounding this dynamically-cool stellar…
Kinematics of hypervelocity stars in the triaxial halo of the Milky Way
Qingjuan Yu, Piero Madau
Hypervelocity stars (HVSs) ejected by the massive black hole at the Galactic center have unique kinematic properties compared to other halo stars. Their trajectories will deviate f…
Evolution of accretion disks around massive black holes: constraints from the demography of active galactic nuclei
Qingjuan Yu, Youjun Lu, Guinevere Kauffmann
Observations have shown that the Eddington ratios (the ratio of the bolometric luminosity to the Eddington luminosity) in QSOs/active galactic nuclei (AGNs) cover a wide range. In…
The Strömgren sphere, the environment and the reionization in the local universe of the highest redshift QSOs
Qingjuan Yu, Youjun Lu
In this paper we investigate the environment and reionization process around the highest redshift QSOs having Gunn-Peterson troughs (z>6.1). Starting with the cosmic density pertur…
The apparent shape of the "Strömgren sphere'' around the highest-redshift QSOs with Gunn-Peterson troughs
Qingjuan Yu
Although the highest redshift QSOs (z>6.1) are embedded in a significantly neutral background universe (mass-averaged neutral hydrogen fraction >1%) as suggested by the Gunn-Peters…
The black hole mass versus velocity dispersion relation in QSOs/Active Galactic Nuclei: observational appearance and black hole growth
Qingjuan Yu, Youjun Lu
Studies of massive black holes (BHs) in nearby galactic centers have revealed a tight correlation between BH mass and galactic velocity dispersion. In this paper we investigate how…
Constraints on QSO models from a relation between the QSO luminosity function and the local black hole mass function
Qingjuan Yu, Youjun Lu
QSOs are believed to be powered by accretion onto massive black holes (BHs). In this paper, assuming that each central BH in nearby galaxies has experienced the QSO phase and ignor…
Ejection of hypervelocity stars by the (binary) black hole(s) in the Galactic center
Qingjuan Yu, Scott Tremaine
We study three processes that eject hypervelocity (>10^3 km/s) stars from the Galactic center: (i) close encounters of two single stars; (ii) tidal breakup of binary stars by the c…
Stellar collisions in galactic centers: black hole growth and color gradients
Qingjuan Yu
We study the effects of stellar collisions, particularly on feeding massive black holes (BHs) and color gradients, in realistic galactic centers. We find that the mass released by…
Observational constraints on growth of massive black holes
Qingjuan Yu, Scott Tremaine
We study the observational constraints on the growth of massive black holes (BHs) in galactic nuclei. We use the velocity dispersions of early-type galaxies obtained by the SDSS an…
Evolution of massive binary black holes
Qingjuan Yu
Since many or most galaxies have central massive black holes (BHs), mergers of galaxies can form massive binary black holes (BBHs). In this paper, we study the evolution of massive…
The relationship between the X-ray variability and the central black hole mass
Youjun Lu, Qingjuan Yu
We assembled a sample of Seyfert 1 galaxies, QSOs and Low-Luminosity Active Galactic Nuclei (LLAGNs) observed by ASCA, whose central black hole masses have been measured. We found…
The effects of relativistic bulk motion of X-ray flares in the corona on the iron Kalpha line in Seyfert 1 galaxies
Youjun Lu, Qingjuan Yu
We study the effects of the bulk motion of X-ray flares on the shape and equivalent width of the iron Kalpha line from an untruncated cold disk around a Kerr black hole using fully…
Fe K_alpha line: A tool to probe massive binary black holes in Active Galactic Nuclei?
Qingjuan Yu, Youjun Lu
Hierarchical mergers of galaxies can form binary black holes (BBHs) since many or most galaxies have central massive black holes (BHs). It is possible that some BBHs exist in activ…
Rayleigh Scattering and Microwave Background Fluctuations
Qingjuan Yu, David N. Spergel, Jeremiah P. Ostriker
During the recombination epoch, cosmic background photons couple not only to free electrons through Thompson scattering, but also to the neutral hydrogen through Rayleigh scatterin…
Resonant capture by inward migrating planets
Qingjuan Yu, Scott Tremaine
We investigate resonant capture of small bodies by planets that migrate inwards, using analytic arguments and three-body integrations. If the orbits of the planet and the small bod…
The Mass-To-Light Function: Antibias and Omega_m
N. A. Bahcall, R. Cen, R. Davé +2
We use large-scale cosmological simulations to estimate the mass-to-light ratio of galaxy systems as a function of scale, and compare the results with observations of galaxies, gro…
Resonant capture, counter-rotating disks, and polar rings
Scott Tremaine, Qingjuan Yu
We suggest that polar rings and/or counter-rotating disks in flattened galaxies can be formed from stars captured at the Binney resonance, where the rate of precession of the angul…
Two Different Accretion Classes in Seyfert 1 Galaxies and QSOs
Youjun Lu, Qingjuan Yu
The mass of the central black hole in Seyfert galaxies and QSOs can be determined from the broad emission lines and the reverberation method. Using the measured black hole mass and…
Iron K-alpha line profiles driven by non-axisymmetric illumination
Qingjuan Yu, Youjun Lu
Previous calculations of Fe K-alpha line profiles are based on axisymmetric emissivity laws. In this paper, we show line profiles driven by non-axial symmetric illumination which r…
The dynamics of Plutinos
Qingjuan Yu, Scott Tremaine
Plutinos are Kuiper-belt objects that share the 3:2 Neptune resonance with Pluto. The long-term stability of Plutino orbits depends on their eccentricity. Plutinos with eccentricit…