QSG.py generates random quasar templates given a model computed with QSG_fit.py. This redshift of spectral lines is what the SDSS measures to determine the distances to quasars and galaxies. ![]() For more distant quasars, these emission lines are shifted to longer wavelengths by the expansion of the universe. The table should at minimum contain the following columns: Bright bands show the emission produced by specific ions of hydrogen, carbon, oxygen, magnesium, and iron. There should be one file per bin in redshift containing as many spectra as desired. Stacked quasar spectra Stacked spectra of more than 46,000 quasars from the SDSS each spectrum has been converted to a single horizontal line, and they are stacked one above the other with the closest quasars at the bottom and the most distant quasars at the top. The code should be provided with a directory containing only the input spectra in table fits format. QSG_fit.py performes the PCA, producing a file containing a model that can go as an input of QSG.py. The code comes with a precomputed model based on SDSS-III BOSS DR12 data able to generate quasar spectra from redshift 0 to 4 per bin of 0.1.
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