Related papers: Finding New High-Redshift Quasars by Asking the Ne…

Luminous quasars at $z>4$ provide key insights into the early Universe. Their rarity necessitates wide-field multi-band surveys to efficiently separate them from the main astrophysical contaminants (i.e., ultracool dwarfs). To expand the…

The recent discoveries of luminous quasars at high redshifts imply that black holes more massive than a few billion solar masses have been assembled already when the universe was less than a billion years old. We show that the existence of…

We present the discovery of three z>5 quasars in the AGN and Galaxy Evolution Survey (AGES) spectroscopic observations of the NOAO Deep Wide-Field Survey (NDWFS) Bootes Field. These quasars were selected as part of a larger Spitzer…

We aim to select quasar candidates based on the two large survey databases, Pan-STARRS and AllWISE. Exploring the distribution of quasars and stars in the color spaces, we find that the combination of infrared and optical photometry is more…

The search for extremely massive high redshift blazars is essential to put strong constraints on the supermassive black holes formation theories. Up to now, the few blazars known to have a redshift larger than 4 have been discovered…

We present a new measurement of the space density of high redshift (3.0<z<4.5), X-ray selected QSOs obtained by exploiting the deep and uniform multiwavelength coverage of the COSMOS survey. We have assembled a statistically large (40…

We report the discovery of a radio loud quasar with a redshift of 4.30. This object, which is the first radio selected quasar with a redshift greater than four, was discovered during an observational investigation into the evolution of the…

This is the second paper in a series aimed at finding high-redshift quasars from five-color (u'g'r'i'z') imaging data taken along the Celestial Equator by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this paper, we…

There is a growing consensus that the emergence of quasars at high redshifts is related to the onset of galaxy formation, suggesting that the detection of concentrations of gas accompanying such quasars should provide clues about the early…

We have conducted a pilot survey for z>3.5 quasars by combining the FIRST radio survey with the SDSS. While SDSS already targets FIRST sources for spectroscopy as quasar candidates, our survey includes fainter quasars and greatly improves…

The census of obscured quasar populations is incomplete, and remains a major unsolved problem, especially at higher redshifts, where we expect a greater density of galaxy formation and quasar activity. We present Gemini GNIRS near-infrared…

We present results on two related topics: 1. A discussion of high redshift candidates (z>4.5), and 2. A study of very small galaxies at intermediate redshifts, both sets being detected in the region of the northern Hubble Deep Field covered…

We report the discovery of five gravitationally lensed quasars from the Sloan Digital Sky Survey (SDSS). All five systems are selected as two-image lensed quasar candidates from a sample of high-redshift (z>2.2) SDSS quasars. We confirmed…

We present a description of the observations and data reduction procedures for an extensive spectroscopic and multi-band photometric study of nine high redshift, optically-selected cluster candidates. The primary goal of the survey is to…

The introduction of low-frequency radio arrays is expected to revolutionize the study of the reionization epoch. Observation of the contrast in redshifted 21cm emission between a large HII region and the surrounding neutral inter-galactic…

We present results of a new, large survey for high-redshift radio-loud quasars, which targets quasars with z>4. The survey is based on the PMN and NVSS radio surveys, optically identified using digitised UKST B, R and I plates. Six new z>4…

We present the results of a systematic search for galaxies in the redshift range z = 6 - 9, within the new, deep, near-infrared imaging of the Hubble Ultra Deep Field provided by the Wide Field Camera 3 (WFC3) on HST. We have performed full…

We calculate the observable properties of the most massive high-redshift galaxies in the hierarchical formation scenario where stellar spheroid and supermassive black hole growth are fueled by gas-rich mergers. Combining high-resolution…

We present the first high redshift (0.3 < z < 1.1) galaxy clusters found by systematically identifying optical low surface brightness fluctuations in the background sky. Using spectra obtained with the Keck telescope and I-band images from…

We have obtained complete redshift information for a sample of 442 radio-loud quasars with flux densities S(11cm) >= 0.25Jy. These come from a completely-identified sample of 878 flat-spectrum radio sources, so there is no optical magnitude…