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Photometric Redshift and Classification for the XMM-COSMOS Sources

Salvato, M. and Hasinger, G. and Ilbert, O. and Zamorani, G. and Brusa, M. and Scoville, N. Z. and Rau, A. and Capak, P. and Arnouts, S. and Aussel, H. and Bolzonella, M. and Buongiorno, A. and Cappelluti, N. and Caputi, K. and Civano, F. and Cook, R. and Elvis, M. and Gilli, R. and Jahnke, K. and Kartaltepe, J. S. and Impey, C. D. and Lamareille, F. and Le Floch, E. and Lilly, S. and Mainieri, V. and McCarthy, P. and McCracken, H. and Mignoli, M. and Mobasher, B. and Murayama, T. and Sasaki, S. and Sanders, D. B. and Schiminovich, D. and Shioya, Y. and Shopbell, P. and Silverman, J. and Smolčić, V. and Surace, J. and Taniguchi, Y. and Thompson, D. and Trump, J. R. and Urry, M. and Zamojski, M. (2009) Photometric Redshift and Classification for the XMM-COSMOS Sources. Astrophysical Journal, 690 (2). pp. 1250-1263. ISSN 0004-637X.

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We present photometric redshifts and spectral energy distribution (SED) classifications for a sample of 1542 optically identified sources detected with XMM in the COSMOS field. Our template fitting classifies 46 sources as stars and 464 as nonactive galaxies, while the remaining 1032 require templates with an active galactic nucleus (AGN) contribution. High accuracy in the derived photometric redshifts was accomplished as the result of (1) photometry in up to 30 bands with high-significance detections, (2) a new set of SED templates, including 18 hybrids covering the far-UV to mid-infrared, which have been constructed by the combination of AGNs and nonactive galaxies templates, and (3) multiepoch observations that have been used to correct for variability (most important for type 1 AGNs). The reliability of the photometric redshifts is evaluated using the subsample of 442 sources with measured spectroscopic redshifts. We achieved an accuracy of σΔz/(1+z_(spec)) = 0.014 for i∗_(AB) < 22.5 (σΔz/(1+z_(spec)) ~ 0.015 for i∗_(AB) < 24.5). The high accuracies were accomplished for both type 2 (where the SED is often dominated by the host galaxy) and type 1 AGNs and QSOs out to z = 4.5. The number of outliers is a large improvement over previous photometric redshift estimates for X-ray-selected sources (4.0% and 4.8% outliers for i∗_(AB) < 22.5 and i∗_(AB) < 24.5, respectively). We show that the intermediate band photometry is vital to achieving accurate photometric redshifts for AGNs, whereas the broad SED coverage provided by mid-infrared (Spitzer/IRAC) bands is important to reduce the number of outliers for normal galaxies.

Item Type:Article
Related URLs:
URLURL TypeDescription
Scoville, N. Z.0000-0002-0438-3323
McCracken, H.0000-0002-9489-7765
Surace, J.0000-0001-7291-0087
Urry, M.0000-0002-0745-9792
Additional Information:© 2009. The American Astronomical Society. Received 2008 August 15; accepted 2008 September 9; published 2008 December 8. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under NASA contract NAS 5-26555. Also based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Also based on data collected at: the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and NASA; the European Southern Observatory under Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory and the National Optical Astronomy Observatory, which are operated by AURA under cooperative agreement with the National Science Foundation; and the Canada–France–Hawaii Telescope with MegaPrime/MegaCam operated as a joint project by the CFHT Corporation CEA/DAPNIA, the NRC and CADC of Canada, the CNRS of France, TERAPIX and the University of Hawaii. We gratefully acknowledge the contributions of the entire COSMOS collaboration consisting of more than 100 scientists. More information on the COSMOS survey is available at We acknowledge the anonymous referee for helpful comments that improved the paper. We also acknowledge the hospitality of the Institute for Astronomy, Hawaii, and the support of the Aspen Center for Physics where the work started and the manuscript was completed. G.H. acknowledges support by the German Deutsche Forschungsgemeinschaft, DFG Leibniz Prize (FKZ HA 1850/ 28-1). This work was supported in part by NASA Grant GO7- 8136A.
Group:COSMOS, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASANAS 5-26555
Deutsche Forschungsgemeinschaft (DFG)FKZ HA 1850/ 28-1
Subject Keywords:catalogs; galaxies: active; methods: miscellaneous
Record Number:CaltechAUTHORS:20090413-145514915
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13958
Deposited By: Kristin Buxton
Deposited On:04 Aug 2009 23:21
Last Modified:28 Jun 2017 21:35

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