相关论文: Detecting and Characterizing Young Quasars I: Syst…
Although the population of luminous quasars rises and falls over a period of 10^9 years, the typical lifetime of individual quasars is uncertain by several orders of magnitude. We show that quasar clustering measurements can substantially…
Nearly 300 quasars have now been found at $z >$ 6, including nine at $z >$ 7. They are thought to form from the collapse of supermassive primordial stars to 10$^4$ - 10$^5$ M$_{\odot}$ black holes at $z \sim$ 20 - 25, which then rapidly…
Luminous distant quasars are unique probes of the high redshift intergalactic medium (IGM) and of the growth of massive galaxies and black holes in the early universe. Absorption due to neutral Hydrogen in the IGM makes quasars beyond a…
The discovery of quasars few hundred megayears after the Big Bang represents a major challenge to our understanding of black holes and galaxy formation and evolution. Their luminosity is produced by extreme gas accretion onto black holes,…
We demonstrate that the UV brightest quasars at z=1-2 live in overdense environments. This is based on an analysis of deep Hubble Space Telescope WFC3 G141 grism spectroscopy of the galaxies along the lines-of-sight to UV luminous quasars…
Luminous high-redshift quasars can be used to probe of the intergalactic medium (IGM) in the early universe because their UV light is absorbed by the neutral hydrogen along the line of sight. They help us to measure the neutral hydrogen…
We present a simple model of how quasars occupy dark matter halos from z=0 to z=5 using the observed mBH-sigma relation and quasar luminosity functions. This provides a way for observers to statistically infer host halo masses for quasar…
We use the spectra of 22,000 nearby early-type galaxies from the Sloan Digital Sky Survey (SDSS) to determine the age distribution of these galaxies as a function of their velocity dispersion sigma_v in the range 100 km/s < sigma_v < 280…
Quasars are among the most luminous objects in the universe, and they can be studied in detail up to the highest known redshift. Assuming that the gas associated with quasars is closely related to the interstellar medium of the host galaxy,…
We present initial results from the first systematic survey of luminous $z\sim 5.5$ quasars. Quasars at $z \sim$ 5.5, the post-reionization epoch, are crucial tools to explore the evolution of intergalactic medium, quasar evolution and the…
Bright quasars, observed when the Universe was less than one billion years old (z>5.5), are known to host massive black holes (~10$^{9}$ M$_{\odot}$), and are thought to reside in the center of massive dark matter overdensities. In this…
Understanding the growth of the supermassive black holes powering luminous quasars, their co-evolution with host galaxies, and impact on the surrounding intergalactic medium depends sensitively on the duration of quasar accretion episodes.…
We have observed a sample of 15 and 8 quasars with redshifts between 0.11 and 0.87 (mean value 0.38) in the J and K' bands respectively. Eleven of the quasars were previously known to be associated with extended emission line regions. After…
We study the prospects of finding the first quasars in the universe with ALMA and JWST. For this purpose, we derive a model for the high-redshift black hole population based on observed relations between the black hole mass and the host…
Constraints on the time-scales of quasar activity are key to understanding the formation and growth of supermassive black holes (SMBHs), quasar triggering mechanisms, and possible feedback effects on their host galaxies. However,…
The duration of quasar accretion episodes is a key quantity for distinguishing between models for the formation and growth of supermassive black holes, the evolution of quasars, and their potential feedback effects on their host galaxies.…
I review recent observations on the evolution of quasars, describe new surveys for quasars at z > 5 and for quasars at z > 3.3 down to luminosities corresponding to L* galaxies, and note the possible connection between the evolution of the…
High-redshift quasars are currently the only probes of the growth of supermassive black holes and potential tracers of structure evolution at early cosmic time. Here we present our candidate selection criteria from the Panoramic Survey…
The overionized regions surrounding high-redshift quasars, known as proximity zones, provide a window into the interaction between supermassive black holes (SMBHs) and the intergalactic medium (IGM) during the epoch of reionization (EoR).…
The identification of bright quasars at z>6 enables detailed studies of supermassive black holes, massive galaxies, structure formation, and the state of the intergalactic medium within the first billion years after the Big Bang. We present…