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This report will discuss several techniques aimed at better understanding of the high-redshift quasar population:
1) Deep ${\rm B_j}$, R and I imaging of the fields centered on the candidates chosen from the double (X-ray and faint galaxies) correlated sample of Bartelmann et al. (1994), from the Palomar Transit Grism Survey (PTGS) of Schneider et al. (1994) and from the known bright $z > 4$ quasars.
The goal of this project is to obtain definitive evidence for or against previously undetected lensing events for a selected sample of quasars and to search for companion objects of these quasars at the same redshift.
2) Analysis of quasar-galaxy correlations in direct V and I band images of the PTGS.
Direct images are searched for excess of faint galaxies around survey quasars. If such excess were observed, it would indicate that quasars were brought into the sample due to amplification by gravitational lensing.
3) Automatic classification of slitless spectra in the PTGS and search for low luminosity and/or small equivalent width quasars near established high redshift quasars.
Grism spectra are classified into broad spectral classes which include representative stellar, galaxy and quasar spectra. Spectra with small equivalent width emission lines near original survey quasars are selected, and follow-up slit spectroscopy of these objects is carried out at the Apache Point Observatory.
