Colors of 2625 Quasars at 0 < z < 5 Measured in the Sloan Digital Sky Survey Photometric System*

We present an empirical investigation of the colors of quasarsin the Sloan Digital Sky Survey(SDSS) photometric system. The sample studied includes 2625 quasarswith SDSS photometry: 1759 quasarsfound during SDSS spectroscopic commissioning and SDSS follow-up observations on other telescopes, 50 matches to FIRST quasars, 573 matches to quasarsfrom the NASA Extragalactic Database, and 243 quasarsfrom two or more of these sources. The quasarsare distributed in a 25 wide stripe centered on the celestial equatorcovering ~529 deg2. Positions (accurate to 02) and SDSS magnitudes are given for the 898 quasarsknown prior to SDSS spectroscopic commissioning. New SDSS quasars, which range in brightness from i* = 15.39 to the photometric magnitude limit of the survey, represent an increase of over 200% in the number of known quasarsin this area of the sky. The ensemble averageof the observed colors of quasarsin the SDSS passbands are well represented by a power-law continuum with αν = -0.5 (fν ∝ να) and are close to those predicted by previous simulations. However, the contributions of the small blue(or λ3000) bump and other strong emission lines have a significant effect upon the colors. The color- redshiftrelation exhibits considerable structure, which may be of use in determining photometric redshiftsfor quasarsfrom their colors alone. The range of colors at a given redshiftcan generally be accounted for by a range in the optical spectral indexwith a distribution αν = -0.5 ± 0.65 (95% confidence), but there is a red tail in the distribution. This tail may be a sign of internal reddening, especially since fainter objects at a given redshifttend to exhibit redder colors than the average. Finally, we show that there is a continuum of properties between quasarsand Seyfert galaxies, and we test the validity of the traditional dividing line (MB = -23) between the two classes of active galactic nuclei.