Abstract
We have imaged 45 quasars from the Sloan Digital Sky Survey (SDSS) with redshifts 1.85 < z < 4.26 in JHKs with the Kitt Peak National Observatory simultaneous quad infrared imaging device imager. By combining these data with optical magnitudes from the SDSS we have computed the rest-frame optical spectral indices of this sample and investigate their relation with quasar redshift. We find a mean spectral index of α o = –0.55 ± 0.42 with a large spread in values. We also find possible evolution of the form α o = (0.148 ± 0.068)z – (0.964 ± 0.200) in the luminosity range –28.0 < Mi < –26.5. Such evolution suggests changes in the accretion process in quasars with time and is shown to have an effect on computed quasar luminosity functions.
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