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

By G. T. Richards, Xiaohui Fan, D. Schneider, D. V. vanden Berk, M. Strauss, D. York, Jay Anderson, S. Anderson, James Annis, N. Bahcall and 51 more. 2000

193 citations recorded by the source corpus.

We present an empirical investigation of the colors of quasars in the Sloan Digital Sky Survey (SDSS) photometric system. The sample studied includes 2625 quasars with SDSS photometry: 1759 quasars found during SDSS spectroscopic commissioning and SDSS follow-up observations on other telescopes, 50 matches to FIRST quasars, 573 matches to quasars from the NASA Extragalactic Database, and 243 quasars from two or more of these sources. The quasars are distributed in a 2.°5 wide stripe centered on the celestial equator covering ∼529 deg2. Positions (accurate to 0.″2) and SDSS magnitudes are given for the 898 quasars known 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 quasars in this area of the sky. The ensemble average of the observed colors of quasars in 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-redshift relation exhibits considerable structure, which may be of use in determining photometric redshifts for quasars from their colors alone. The range of colors at a given redshift can generally be accounted for by a range in the optical spectral index with 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 redshift tend to exhibit redder colors than the average. Finally, we show that there is a continuum of properties between quasars and Seyfert galaxies, and we test the validity of the traditional dividing line (MB = -23) between the two classes of active galactic nuclei.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/097c9dd0460834ea945d67eb5c51ba81c1d3e04e

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Citations in the corpus

ARE THE VARIATIONS IN QUASAR OPTICAL FLUX DRIVEN BY THERMAL FLUCTUATIONS? (2009, methodology): “However, the spectra are not flux-calibrated, so the luminosities at 1350, 3000, and 5100Å were estimated from the photometric data, assuming a power-law continuum with α = 0.5, fν ∝ ν−α (Richards et al. 2001).”
Red and Reddened Quasars in the Sloan Digital Sky Survey (2003, methodology): “The color distribution of quasars (Webster et al. 1995; Francis, Whiting, & Webster 2000; Brotherton et al. 2001; Richards et al. 2001) and the discovery of a few examples of highly reddened radio-selected quasars (Gregg et al. 2002; White et al. 2003) strongly suggest that a sizeable population of…”
The Sloan Digital Sky Survey Quasar Catalog. I. Early Data Release (2001, background): “The most comprehensive investigations, both using samples containing more than 2000 quasars, are the quasar color-redshift relation for redshifts between 0 and 5 (Richards et al. 2001a) and the construction of a very high signal-to-noise ratio composite quasar spectrum (Vanden Berk et al. 2001).”
The Sloan Digital Sky Survey Quasar Catalog. IV. Fifth Data Release (2007, background): “Quasar Colors It has long been known that the majority of quasars inhabit a restricted range in photometric color, and the large sample size and accurate photometry of the SDSS revealed a relatively tight color-redshift correlation for quasars (Richards et al. 2001).”
THE SLOAN DIGITAL SKY SURVEY QUASAR CATALOG. V. SEVENTH DATA RELEASE (2010, background): “It has long been known that the majority of optically selected quasars inhabit a restricted range in photometric color, and the large sample size and accurate photometry of the SDSS revealed a tight color–redshift correlation for quasars (Richards et al. 2001, 2003; Paper IV).”
Star Counts Redivivus. IV. Density Laws through Photometric Parallaxes (2002, methodology): “Using the quasar luminosity function of Kron et al. (1991), convolved with the SDSS color distribution of the quasars listed in Richards et al. (2001), transformed from SDSS to standard filters using the transformations of Fukugita (1996), we estimate that this color-magnitude bin should have a…”
THE SDSS-IV EXTENDED BARYON OSCILLATION SPECTROSCOPIC SURVEY: QUASAR TARGET SELECTION (2015, background): “In general, XDQSOz selects similar regions of color space to SDSS targets from earlier surveys (e.g., Richards et al. 2001), with the majority of the quasar-star separation occuring in the ugr filters.”
Candidate Type II Quasars from the Sloan Digital Sky Survey. I. Selection and Optical Properties of a Sample at 0.3 < Z < 0.83 (2003, background): “The main quasar locus exhibits complicated redshiftdependent behavior as emission lines move in and out of the filters (see Richards et al. 2001 for details); vertical lines indicate redshifts at which color changes are expected to occur.”
Optical and Radio Properties of Extragalactic Sources Observed by the FIRST Survey and the Sloan Digital Sky Survey (2002, background): “In the redder bands they are not such extreme outliers as in the bluer bands, as noted by Richards et al. (2001).”
Binary Quasars in the Sloan Digital Sky Survey: Evidence for Excess Clustering on Small Scales (2005, methodology): “This threshold implies a certain level of completeness for our survey, which varies with redshift, as the dispersion in the color-redshift relation of quasars depends on redshift (Richards et al. 2001a).”
Sloan Digital Sky Survey: Early Data Release (2002, background): “Richards et al. (2001) and Schneider et al. (2002) compare SDSS quasar redshifts with those from the NASA/IPAC Extragalactic Database (NED), and they find excellent No. 1, 2002 SDSS EARLY DATA RELEASE 543 agreement; in three cases, they found that the NED redshifts were wrong, but in no case was…”
Composite Quasar Spectra from the Sloan Digital Sky Survey (2001, methodology): “The spectra were obtained as part of the commissioning phase of the SDSS. Details of the quasar candidate target selection and spectroscopic data reduction will be given in future papers (Richards et al. 2001a ; Newberg et al. 2001 ; Frieman et al. 2001).”
A Survey of z > 5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at z ∼ 6 (2001, methodology): “Colors of z > 5.8 quasars The observed colors of quasars evolve strongly with redshift, as the intrinsic emission and the intervening absorption spectral features move through the SDSS filter system (Fan 1999, Richards et al. 2001a).”
Unusual Broad Absorption Line Quasars from the Sloan Digital Sky Survey (2002, background): “Quasars do not have to have BAL troughs to be reddened (Richards et al. 2001), but BAL quasars are more often reddened than normal QSOs are (Richards 2001), and there is evidence for dust in the absorbing region of at least one BAL quasar (de Kool et al. 2001).”
The Sloan Digital Sky Survey View of the Palomar-Green Bright Quasar Survey (2005, background): “[2]) have redder g i colors than those with R < 1 (see Richards et al. 2001).”
The Sloan Digital Sky Survey Quasar Survey: Quasar Luminosity Function from Data Release 3 (2006, methodology): “Following Richards et al. (2001, 2003) we subtract the mean color as a function of redshift from the observed color, removing the mean emission line contribution from the colors and allowing for a redshift-independent color comparison.”
Dust Reddening in Sloan Digital Sky Survey Quasars (2004, methodology): “Colors as a Function of Redshift We follow the convention of Richards et al. (2001, 2003) and define ‘‘red’’ quasars using colors relative to those of typical quasars as a function of redshift.”
Active galactic nuclei: what’s in a name? (2017, background): “Broad band photometry is sensitive to the presence of broad emission lines in the various filters as a function of redshift, as they alter the otherwise very typical colours of the AGN that separate them from the stellar locus (see, e.g. Richards et al. 2001, Fig.”
Early Growth and Efficient Accretion of Massive Black Holes at High Redshift (2003, background): “…by their broad lines, it is not clear whether the discovery surveys with their selection criteria (and crude spectral resolution in early surveys) would be able to identify quasars with such narrow lines; even the SDSS quasar identification is not well-defined at present (Richards et al. 2001).”