QSOs are another area where J-PAS will have a major impact. The narrow-band filter system is ideal to detect the broad emission lines of type-1 quasars, and we expect to identify and measure with high accuracy the redshifts of more than 3 million of these objects, up to redshifts of z~6. This quasar survey will be by far the largest in existence, improving on SDSS by a factor of >20, and allowing, for the first time, a measurement of large-scale structure with quasars alone. Even BAOs will be observable with quasars, both in the angular and in the radial directions. Moreover, the dataset will also be ideal to explore issues such as the clustering and bias of quasars, their luminosity function, duty cycles, etc. Another exciting application of the quasar survey is the search for strongly lensed systems: J-PAS will provide hundreds of multiple-image candidates.
J-PAS will provide a map of galaxies (with well defined redshifts) in the neighborhoods of the observed target lines of all quasars, which will be extremely useful to correlate absorbers with the galaxies observed in the line of sight, providing valuable information on the gas distribution around the galaxies. The most luminous star-forming galaxies at redshifts z ~2.5 will be detectable with J-PAS narrow-band photometry by means of their Lyman continuum break, the Lyα forest absorption, and possibly Lyα emission line. This will allow the study of this galaxy population and its clustering properties over an unprecedentedly large volume.