TY - JOUR
T1 - Quasar photometric redshifts and candidate selection
T2 - A new algorithm based on optical and mid-infrared photometric data
AU - Yang, Qian
AU - Wu, Xue Bing
AU - Fan, Xiaohui
AU - Jiang, Linhua
AU - McGreer, Ian
AU - Green, Richard
AU - Yang, Jinyi
AU - Schindler, Jan Torge
AU - Wang, Feige
AU - Zuo, Wenwen
AU - Fu, Yuming
N1 - Funding Information:
We acknowledge the use of SDSS photometric data. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III website ishttp://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.
Funding Information:
We acknowledge the use of PS1 photometric data. The PS1 has been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cum-bres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under Grant No. AST-1238877, the University of Maryland, and Eotvos Lorand University (ELTE).
Funding Information:
We gratefully acknowledge the support from the Ministry of Science and Technology of China under grant 2016YFA0400703, NSFC grants No.11373008 and 11533001, and the National Key Basic Research Program of China 2014CB845700.
Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.
PY - 2017/12
Y1 - 2017/12
N2 - We present a new algorithm to estimate quasar photometric redshifts (photo-zs), by considering the asymmetries in the relative flux distributions of quasars. The relative flux models are built with multivariate Skew-t distributions in the multidimensional space of relative fluxes as a function of redshift and magnitude. For 151,392 quasars in the SDSS, we achieve a photo-z accuracy, defined as the fraction of quasars with the difference between the photo-z zp and the spectroscopic redshift zs, /Δz/ = /zs - zp/ (1 + zs) within 0.1, of 74%. Combining the WISE W1 and W2 infrared data with the SDSS data, the photo-z accuracy is enhanced to 87%. Using the Pan-STARRS1 or DECaLS photometry with WISE W1 and W2 data, the photo-z accuracies are 79% and 72%, respectively. The prior probabilities as a function of magnitude for quasars, stars, and galaxies are calculated, respectively, based on (1) the quasar luminosity function, (2) the Milky Way synthetic simulation with the Besançon model, and (3) the Bayesian Galaxy Photometric Redshift estimation. The relative fluxes of stars are obtained with the Padova isochrones, and the relative fluxes of galaxies are modeled through galaxy templates. We test our classification method to select quasars using the DECaLS g, r, z, and WISE W1 and W2 photometry. The quasar selection completeness is higher than 70% for a wide redshift range 0.5 < z < 4.5, and a wide magnitude range 18 < r < 21.5 mag. Our photo-z regression and classification method has the potential to extend to future surveys. The photo-z code will be publicly available.
AB - We present a new algorithm to estimate quasar photometric redshifts (photo-zs), by considering the asymmetries in the relative flux distributions of quasars. The relative flux models are built with multivariate Skew-t distributions in the multidimensional space of relative fluxes as a function of redshift and magnitude. For 151,392 quasars in the SDSS, we achieve a photo-z accuracy, defined as the fraction of quasars with the difference between the photo-z zp and the spectroscopic redshift zs, /Δz/ = /zs - zp/ (1 + zs) within 0.1, of 74%. Combining the WISE W1 and W2 infrared data with the SDSS data, the photo-z accuracy is enhanced to 87%. Using the Pan-STARRS1 or DECaLS photometry with WISE W1 and W2 data, the photo-z accuracies are 79% and 72%, respectively. The prior probabilities as a function of magnitude for quasars, stars, and galaxies are calculated, respectively, based on (1) the quasar luminosity function, (2) the Milky Way synthetic simulation with the Besançon model, and (3) the Bayesian Galaxy Photometric Redshift estimation. The relative fluxes of stars are obtained with the Padova isochrones, and the relative fluxes of galaxies are modeled through galaxy templates. We test our classification method to select quasars using the DECaLS g, r, z, and WISE W1 and W2 photometry. The quasar selection completeness is higher than 70% for a wide redshift range 0.5 < z < 4.5, and a wide magnitude range 18 < r < 21.5 mag. Our photo-z regression and classification method has the potential to extend to future surveys. The photo-z code will be publicly available.
KW - Catalogs
KW - Cosmology: observations
KW - Galaxies: distances and redshifts
KW - Methods: statistical
KW - Quasars: general
UR - http://www.scopus.com/inward/record.url?scp=85036630561&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85036630561&partnerID=8YFLogxK
U2 - 10.3847/1538-3881/aa943c
DO - 10.3847/1538-3881/aa943c
M3 - Article
AN - SCOPUS:85036630561
SN - 0004-6256
VL - 154
JO - Astronomical Journal
JF - Astronomical Journal
IS - 6
M1 - 269
ER -