This file describes the contents of the tarred and gzipped data files "absorber_spectra" and 
"non_absorber_spectra". The first file contains spectral data corresponding to those quasars 
whose spectra contain MgII absorption. (The MgII absorber catalog is available separately.) 
The second file contains spectral data for those quasars without detectable MgII absorption 
lines in their spectra. The two sets of spectra have been separated only for convenience, 
and to make the files small enough for download. 

For each SDSS quasar spectrum searched for MgII absorption, an ascii file with the name format 
spSpec-MJD-plate-fiber is included.  

The first row contains the emission redshift of the quasar.
The columns of the remaining rows correspond to:
Column 1: wavelength [A]
Column 2: flux [10^-16 erg cm^-2 s^-1 A^-1]
Column 3: flux error [10^-16 erg cm^-2 s^-1 A^-1]
Column 4: psuedo-continuum fit [10^-16 erg cm^-2 s^-1 A^-1]
Column 5: W_{lim} [A]

W_{lim} is the minimum detectable rest equivalent width of the MgII 2796 line. When integrated 
over all sightlines, one can derive the total number of redshift intervals surveyed as a function 
of W_{lim} and redshift.

See Quider et al. (2010) for details.