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Being observed only one billion years after the Big Bang, z ~ 7 quasars are a unique opportunity for exploring the early Universe. However, only two z ~ 7 quasars have been discovered in near-infrared surveys: the quasars ULAS J1120+0641 and ULAS J1342+0928 at z = 7.09 and z = 7.54, respectively. The Canada-France High-z Quasar Survey in the Near Infrared (CFHQSIR) has been carried out to search for z ~ 7 quasars using near-infrared and optical imaging from the Canada-France Hawaii Telescope (CFHT). Our data consist of $rm{sim 130,deg^{2}}$ of Wide-field Infrared Camera (WIRCam) Y-band images up to a 5{sigma} limit of $rm{Y_{AB}}$ ~ 22.4 distributed over the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) Wide fields. After follow-up observations in J band, a first photometric selection based on simple colour criteria led us to identify 36 sources with measured high-redshift quasar colours. However, we expect to detect only ~ 2 quasars in the redshift range 6.8 < z < 7.5 down to a rest-frame absolute magnitude of $rm{M_{1450}}$ = -24.6. With the motivation of ranking our high-redshift quasar candidates in the best possible way, we developed an advanced classification method based on Bayesian formalism in which we model the high-redshift quasars and low-mass star populations. The model includes the colour diversity of the two populations and the variation in space density of the low-mass stars with Galactic latitude, and it is combined with our observational data. For each candidate, we compute the probability of being a high-redshift quasar rather than a low-mass star. This results in a refined list of the most promising candidates. Our Bayesian selection procedure has proven to be a powerful technique for identifying the best candidates of any photometrically selected sample of objects, and it is easily extendable to other surveys.
Context. Most observational results on the high redshift restframe UV-bright galaxies are based on samples pinpointed using the so called dropout technique or Ly-alpha selection. However, the availability of multifilter data allows now replacing the
We present the discovery of the first high redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an i dropoutout in PS1, confirmed photometrically with th
We present a submillimetre continuum survey (SCUBA2 High rEdshift bRight quasaR surveY, hereafter SHERRY) of 54 high redshift quasars at $5.6<z<6.9$ with quasar bolometric luminosities in a range of (0.2$-$$ 5)times10^{14},L_{odot}$, using the Submil
We identify 885,503 type 1 quasar candidates to i<22 using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS), while mid-IR phot
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 their lensi