Color-Redshift Relations and Photometric Redshift Estimations of Quasars in Large Sky Surveys

With a recently constructed composite quasar spectrum and the χ2 minimization technique, we describe a general method for estimating the photometric redshifts of a large sample of quasars by deriving theoretical color-redshift relations and comparing the theoretical colors with the observed ones. We estimated the photometric redshifts from the 5-band SDSS photometric data of 18678 quasars in the first major data release of SDSS and compared them with their spectroscopic redshifts. The difference is less than 0.1 for 47% of the quasars and less than 0.2for 68%. Based on the calculation of the theoretical color-color diagrams of stars,galaxies and quasars both on the SDSS system and on the BATC system, we expect that we would be able to select candidates of high redshift quasars more efficaciously with the latter than with the former, provided the BATC survey can detect objects with magnitudes fainter than 21.

作 者： Xue-Bing Wu Wei Zhang Xu Zhou   作者單位： Xue-Bing Wu,Wei Zhang(Department of Astronomy, School of Physics, Peking University, Beijing 100871)

Xu Zhou(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012) 

刊 名： 天體物理學報(英文版)  ISTIC SCI 英文刊名： CHINESE JOURNAL OF ASTRONOMY AND ASTROPHYSICS  年，卷(期)： 2004 4(1)  分類號： P1  關鍵詞： galaxies: photometry - quasars: general - quasars: emission lines - surveys  

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