The catalog contains all PQSO > 0.5 objects with dereddened i-band
magnitude GE 17.8 and LT 21.5 and the following important tags:

pqsolowz  - z < 2.2 quasar probability
pqsomidz - 2.2 <= z <= 3.5 quasar probability
pqsohiz - z > 3.5 quasar probability
pqso - sum of previous three
peakz - MAP redshift (maximum a-posteriori)
peakprob - probability of the main redshift peak (integrated between the limits where the PDF reaches 1./5.2)
peakfwhm - FWHM of the main peak
otherz
otherprob      --> up to 5 other redshift peaks in the redshift PDF (if these are all 0. then there were less than 5 peaks)
otherfwhm
npeaks - number of peaks (regions where the redshift PDF is above 1./5.2)
bitmask - BOSS target selection bitmask
good - 'good' flag from the XDQSO paper (zero everywhere)

psfflux - undereddend PSF flux in nano-maggies
psfflux_ivar - undereddened PSF flux inverse variance in inverse nano-maggies-squared
extinction - extinction in ugriz
ra
dec
objid, run, rerun, camcol, field, id - SDSS idenifier
photometric - ueber-calibration flag of photometricity of the run (see XDQSO paper)

psfmag - dereddened PSF magnitude
psfmagerr - uncertainty in dereddened PSF magnitude
extinction_u - extinction in u

Jo Bovy, NYU (03/02/2011)