Photometric redshift and classification for the XMM-COSMOS sources

• Main Authors: Salvato, M, Hasinger, G, Ilbert, O, Zamorani, G, Brusa, M, Scoville, N, Rau, A, Capak, P, Arnouts, S, Aussel, H, Bolzonella, M, Buongiorno, A, Cappelluti, N, Caputi, K, Civano, F, Cook, R, Elvis, M, Gilli, R, Jahnke, K, Kartaltepe, J. S, Impey, C. D, Lamareille, F, Floch, E. Le, Lilly, S, Mainieri, V, McCarthy, P, McCracken, H, Mignoli, M, Mobasher, B, Murayama, T, Sasaki, S, Sanders, D. B, Schiminovich, D, Shioya, Y, Shopbell, P, Silvermann, J, Smolcic, V, Surace, J, Taniguchi, Y, Thompson, D, Trump, J. R, Urry, M, Zamojski, M
• Format: Journal Article
• Language: English
• Published: 11-09-2008
• Subjects: Physics - Astrophysics of Galaxies; Physics - Cosmology and Nongalactic Astrophysics; Physics - Earth and Planetary Astrophysics; Physics - High Energy Astrophysical Phenomena; Physics - Instrumentation and Methods for Astrophysics; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.0809.2098

Astrophys.J.690:1250-1263,2009 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 non-active galaxies, while the remaining 1032 require templates with
an 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 AGN and non-active galaxies templates, and 3) multi-epoch
observations that have been used to correct for variability (most important for
type 1 AGN). The reliability of the photometric redshifts is evaluated using
the sub-sample of 442 sources with measured spectroscopic redshifts. We
achieved an accuracy of $\sigma_{\Delta z/(1+z_{spec})} = 0.014$ for
i$_{AB}^*<$22.5 ($\sigma_{\Delta z/(1+z_{spec})} \sim0.015$ 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 AGN 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 AGN, whereas the broad SED coverage provided by mid infrared
(Spitzer/IRAC) bands is important to reduce the number of outliers for normal
galaxies.