A search for the first z~7 QSOs

Tomo GOTO (ifa)

  High-redshift QSOs are highly important objects in various
 scientific aspects. For example, their spectra will reveal the onset of
 reionization of the intergalactic medium (Gunn-Peterson trough).
 The assembly of super massive black holes with billion solar masses in a timescale shorter than
1 Gyr yields strong constraints on black hole formation theories.
The abundance and evolution of such QSOs can provide sensitive tests for models of QSO and galaxy evolution. 

 However, the current high-z QSO searches based on the optical large
 surveys have a limitation at $z<6.5$ due to the reward sensitivity
 limit of the optical CCD detectors. Therefore, to extend the search
 for the QSOs to $z\sim7$, we need a large near-infrared (nearIR) sky
 survey, which has been technically difficult due to the small size of
 a near-infrared detector. The UKIRT deep sky survey (UKIDSS; Warren
 et al. 2007) is the first near-infrared survey that observes large
 enough sky (4000 deg$^2$) to find rare high-z QSOs.  By combining
 this near-infrared data with deep optical imaging from the Sloan
 Digital Sky Survey (SDSS; York et al. 2000), especially deeper data
 in the SDSS southern, and even deeper optical data from the Panoramic
 Survey Telescope \& Rapid Response System1 (Pan-STARRS; Kaiser 2007),
 which the University of Hawaii operates, we aim to find the first
 $z\sim7$ QSOs. These QSOs will be used to directly measure the cosmic
 reionization history for the first time at $z\sim$7.

 In addition, I will also mention on-going work on the 50 Mpc scale environment and host galaxies of known z~6 QSOs.