Infrared Imaging of SDSS Quasars: Implications for the Quasar K correction

TL;DR

This study uses infrared imaging of SDSS quasars to analyze their spectral indices and explores how these indices evolve with redshift, impacting quasar luminosity calculations.

Contribution

It provides the first combined infrared and optical analysis of SDSS quasars, revealing spectral index evolution with redshift and its implications for luminosity functions.

Findings

Mean spectral index <alpha_o> = -0.55 +/- 0.42

Possible evolution of alpha_o with redshift

Impacts on quasar luminosity function calculations

Abstract

We have imaged 45 quasars from the Sloan Digital Sky Survey (SDSS) with redshifts 1.85 < z < 4.26 in JHKs with the KPNO SQIID imager. By combining these data with optical magnitudes from the SDSS we have computed the restframe optical spectral indices of this sample and investigate their relation to quasar redshift. We find a mean spectral index of <alpha_o> = -0.55+/-0.42 with a large spread in values. We also find possible evolution of the form alpha_o = (0.148+/-0.068)z - (0.964+/-0.200)$ in the luminosity range -28.0 < M_i < -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.