An Empirical Algorithm for Broad-band Photometric Redshifts of Quasars from the Sloan Digital Sky Survey

Abstract

We present an empirical algorithm for obtaining photometric redshifts of quasars using 5-band Sloan Digital Sky Survey (SDSS) photometry. Our algorithm generates an empirical model of the quasar color-redshift relation, compares the colors of a quasar candidate with this model, and calculates possible photometric redshifts. Using the 3814 quasars of the SDSS Early Data Release Quasar Catalog to generate a median color-redshift relation as a function of redshift we find that, for this same sample, 83% of our predicted redshifts are correct to within |Delta z|<0.3. The algorithm also determines the probability that the redshift is correct, allowing for even more robust photometric redshift determination for smaller, more restricted samples. We apply this technique to a set of 8740 quasar candidates selected by the final version of the SDSS quasar-selection algorithm. The photometric redshifts assigned to non-quasars are restricted to a few well-defined values. In addition, 90% of the objects with spectra that have photometric redshifts between 0.8 and 2.2 are quasars with accurate (|Delta z|<0.3) photometric redshifts. Many of these quasars lie in a single region of color space; judicious application of color-cuts can effectively select quasars with accurate photometric redshifts from the SDSS database. When the SDSS is complete, this technique will allow the determination of photometric redshifts for ~10^6 faint SDSS quasar candidates, enabling advances in our knowledge of the quasar luminosity function, gravitational lensing of quasars, and correlations among quasars and between galaxies.

arXiv comment34 pages, 12 figures (5 color), accepted by ApJS; higher resolution version available at http://www.astro.princeton.edu/~gtr/sdssqsophotoz.ps

References in corpus (25)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Sloan Digital Sky Survey: Technical Summary
• The Sloan Digital Sky Survey Photometric Camera
• The u'g'r'i'z' Standard Star Network
• The Second Data Release of the Sloan Digital Sky Survey
• Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample
• The First Data Release of the Sloan Digital Sky Survey
• Astrometric Calibration of the Sloan Digital Sky Survey
• A photometricity and extinction monitor at the Apache Point Observatory
• An Efficient Algorithm for Positioning Tiles in the Sloan Digital Sky Survey
• A Modified Magnitude System that Produces Well-Behaved Magnitudes, Colors, and Errors Even for Low Signal-to-Noise Ratio Measurements
• Red and Reddened Quasars in the Sloan Digital Sky Survey
• Dust Reddening in SDSS Quasars
• Colors of 2625 Quasars at 0<z<5 Measured in the Sloan Digital Sky Survey Photometric System
• Efficient Photometric Selection of Quasars from the Sloan Digital Sky Survey: 100,000 z<3 Quasars from Data Release One
• The evolution of faint AGN between z~1 and z~5 from the COMBO-17 survey
• Faint Galaxies in deep ACS observations
• The Sloan Digital Sky Survey Quasar Catalog II. First Data Release
• The Sloan Digital Sky Survey Quasar Catalog I. Early Data Release
• Photometric Redshifts for Galaxies in the GOODS Southern Field
• Photometric Redshifts of Quasars
• Photometric redshifts from reconstructed QSO templates
• Multi-color Classification in the Calar Alto Deep Imaging Survey
• The Space Density of High-Redshift QSOs in the GOODS Survey
• Towards More Precise Photometric Redshifts: Calibration Via CCD Photometry

Cited by in corpus (70)

• Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars
• The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release
• The SDSS Quasar Survey: Quasar Luminosity Function from Data Release Three
• The Sloan Digital Sky Survey Quasar Catalog IV. Fifth Data Release
• Data Mining and Machine Learning in Astronomy
• Efficient Photometric Selection of Quasars from the Sloan Digital Sky Survey: II. ~1,000,000 Quasars from Data Release Six
• Fitting the integrated Spectral Energy Distributions of Galaxies
• Binary Quasars in the Sloan Digital Sky Survey: Evidence for Excess Clustering on Small Scales
• Detection of Cosmic Magnification with the Sloan Digital Sky Survey
• The clustering of intermediate redshift quasars as measured by the Baryon Oscillation Spectroscopic Survey
• Efficient Photometric Selection of Quasars from the Sloan Digital Sky Survey: 100,000 z<3 Quasars from Data Release One
• The 2dF-SDSS LRG and QSO Survey: The z<2.1 Quasar Luminosity Function from 5645 Quasars to g=21.85
• Average Extinction Curves and Relative Abundances for QSO Absorption Line Systems at 1 <= z_abs < 2
• Measuring the galaxy-mass and galaxy-dust correlations through magnification and reddening
• First Measurement of the Clustering Evolution of Photometrically-Classified Quasars
• Clustering Analyses of 300,000 Photometrically Classified Quasars--I. Luminosity and Redshift Evolution in Quasar Bias
• Clustering of intermediate redshift quasars using the final SDSS III-BOSS sample
• Photometric Redshifts in the IRAC Shallow Survey
• Binary Quasars at High Redshift I: 24 New Quasar Pairs at z ~ 3-4
• Photometric redshifts and quasar probabilities from a single, data-driven generative model
• Chandra Observations of the Highest Redshift Quasars from the Sloan Digital Sky Survey
• Quasar Clustering at $25\kpch$ from a Complete Sample of Binaries
• SDSS quasars in the WISE preliminary data release and quasar candidate selection with optical/infrared colors
• Investigation of two Fermi-LAT gamma-ray blazars coincident with high-energy neutrinos detected by IceCube
• The Field X-ray AGN Fraction to z=0.7 from the Chandra Multiwavelength Project and the Sloan Digital Sky Survey
• Robust Machine Learning Applied to Astronomical Datasets III: Probabilistic Photometric Redshifts for Galaxies and Quasars in the SDSS and GALEX
• Photometric redshifts for the next generation of deep radio continuum surveys - I: Template fitting
• A Full Year's Chandra Exposure on SDSS Quasars from the Chandra Multiwavelength Project
• Eight-Dimensional Mid-Infrared/Optical Bayesian Quasar Selection
• AGN Populations in Large Volume X-ray Surveys: Photometric Redshifts and Population Types found in the Stripe 82X Survey
• Bayesian High-Redshift Quasar Classification from Optical and Mid-IR Photometry
• Sloan Digital Sky Survey III Photometric Quasar Clustering: Probing the Initial Conditions of the Universe using the Largest Volume
• Quasar candidate selection and photometric redshift estimation based on SDSS and UKIDSS data
• The Clustering of High-Redshift (2.9 $\le$ z $\le$ 5.1) Quasars in SDSS Stripe 82
• The High Redshift Integrated Sachs-Wolfe Effect
• Robust Machine Learning Applied to Astronomical Datasets II: Quantifying Photometric Redshifts for Quasars Using Instance-Based Learning
• Incorporating Photometric Redshift Probability Density Information into Real-Space Clustering Measurements
• Photometric Reverberation Mapping of the Broad Emission Line Region in Quasars
• Efficient Selection of Quasar Candidates Based on Optical and Infrared Photometric Data Using Machine Learning
• Finding Galaxy Groups In Photometric Redshift Space: the Probability Friends-of-Friends (pFoF) Algorithm
• The Extremely Luminous Quasar Survey (ELQS) in the SDSS footprint I.: Infrared Based Candidate Selection
• The Spectral Energy Distributions of Active Galactic Nuclei
• The Spectral Energy Distributions of Active Galactic Nuclei
• Astrometric Redshifts for Quasars
• Finding Quasars behind the Galactic Plane. I. Candidate Selections with Transfer Learning
• Quasar Photometric Redshifts and Candidate Selection: A New Algorithm Based on Optical and Mid-Infrared Photometric Data
• VLBA Imaging Polarimetry of Active Galactic Nuclei - An Automated Approach
• Estimating Photometric Redshifts of Quasars via K-nearest Neighbor Approach Based on Large Survey Databases
• The ChaMP Extended Stellar Survey (ChESS): Photometric and Spectroscopic Properties of Serendipitously Detected Stellar X-ray Sources
• Assessing the photometric redshift precision of the S-PLUS survey: the Stripe-82 as a test-case
• On estimating redshift and luminosity distributions in photometric redshift surveys
• Caught in the Act: Discovery of a Physical Quasar Triplet
• A Multiwavelength Study of Binary Quasars and Their Environments
• A Southern Photometric Quasar Catalog from the Dark Energy Survey Data Release 2
• Use of neural networks for the identification of new z>=3.6 QSOs from FIRST-SDSS DR5
• QSO photometric redshifts using machine learning and neural networks
• Photometric Redshift Estimation for Quasars by Integration of KNN and SVM
• QSO photometric redshifts from SDSS, WISE and GALEX colours
• QSO Lensing Magnification: A Comparison of 2QZ and SDSS Results
• Correlation function of quasars in real and redshift space from the Sloan Digital Sky Survey Data Release 7
• Intervening or associated? Machine learning classification of redshifted H I 21-cm absorption
• QSO redshift estimates from optical, near-infrared and ultraviolet colours
• Quasar photometric redshifts from incomplete data using Deep Learning
• The optical luminosity function of LOFAR radio-selected quasars at $1.4\le z\le 5.0$ in the NDWFS-Boötes field
• Deep CFHT Y-band Imaging of VVDS-F22 Field: II. Quasar Selection and Quasar Luminosity Function
• Redshifts of radio sources in the Million Quasars Catalogue from machine learning
• Discovering bright quasars at intermediate redshifts based on the optical/near-IR colors
• Z-Sequence: Photometric redshift predictions for galaxy clusters with sequential random k-nearest neighbours
• Machine learning techniques for astrophysical modelling and photometric redshift estimation of quasars in optical sky surveys
• A 43-GHz Survey in the ELAIS N2 Area