Photometric Redshifts of Galaxies in COSMOS

Abstract

We measure photometric redshifts and spectral types for galaxies in the COSMOS survey. We use template fitting technique combined with luminosity function priors and with the option to simultaneously estimate dust extinction (i.e. E(B-V)) for each galaxy.Our estimated redshifts are accurate to i<25 and z~1.2. Using simulations with sampling and noise characteristics similar to those in COSMOS, the accuracy and reliability is estimated for the photometric redshifts as a function of the magnitude limits of the sample, S/N ratios and the number of bands used. From the simulations we find that the ratio of derived 95% confidence interval in the redshift probability distribution to the estimated photometric redshift (D95) can be used to identify and exclude the catastrophic failures in the photometric redshift estimates. We compare the derived redshifts with high-reliability spectroscopic redshifts for a sample of 868 normal galaxies with z < 1.2 from zCOSMOS. Considering different scenarios, depending on using prior, no prior and/or extinction, we compare the photometric and spectroscopic redshifts for this sample. This corresponds to an rms scatter of 0.031, with a small number of outliers (<2.5%). We also find good agreement (rms=0.10) between photometric and spectroscopic redshifts for Type II AGNs. We compare results from our photometric redshift procedure with three other independent codes and find them in excellent agreement. We show preliminary results, based on photometric redshifts for the entire COSMOS sample (to i < 25 mag.).

38 pages; 14 Figures; 7 Tables. Accepted for Publication in ApJS. COSMOS Special Issue

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• The Chandra COSMOS Survey, I: Overview and Point Source Catalog
• Weak Gravitational Lensing with COSMOS: Galaxy Selection and Shape Measurements
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• The Cosmic Evolution Survey (COSMOS): Subaru Observations of the HST COSMOS Field
• Correlation of CMB with large-scale structure: I. ISW Tomography and Cosmological Implications
• The XMM-Newton wide-field survey in the COSMOS field: VI. Statistical properties of clusters of galaxies
• COSMOS: 3D weak lensing and the growth of structure
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• HiZELS: a high redshift survey of H-alpha emitters. I: the cosmic star-formation rate and clustering at z=2.23
• The Structures of Distant Galaxies - III: The Merger History of over 20,000 Massive Galaxies at z < 1.2
• Large Structures and Galaxy Evolution in COSMOS at z < 1.1
• The ALHAMBRA Project: A large area multi medium-band optical and NIR photometric survey
• The star-formation history of K-selected galaxies
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• Precision photometric redshift calibration for galaxy-galaxy weak lensing
• The effects of environment on morphological evolution between 0<z<1.2 in the COSMOS Survey
• A New Look at Massive Clusters: weak lensing constraints on the triaxial dark matter halos of Abell 1689, Abell 1835, & Abell 2204
• The evolution of early and late type galaxies in the COSMOS up to z~1.2
• The H$\alpha$ Luminosity Function and Star Formation Rate at $z\approx 0.24$ in the Cosmos 2 Square-Degree Field
• The Cosmic Evolution Survey (COSMOS): a large-scale structure at z=0.73 and the relation of galaxy morphologies to local environment
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• The angular correlations of galaxies in the COSMOS field
• A combined analysis of 3D Weak Lensing, Lyman-alpha forest and WMAP year three data
• The [OII]3727 Luminosity function and Star Formation Rate at z~1.2 in the COSMOS 2 Square-degree Field and the Subaru Deep Field
• A wide angle tail radio galaxy in the COSMOS field: evidence for cluster formation
• Relation Between Stellar Mass and Star Formation Activity in Galaxies
• Quantifying systematic uncertainties in supernova cosmology
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• SuperNova Acceleration Probe (SNAP): Investigating Photometric Redshift Optimization
• Mock galaxy redshift catalogues from simulations: implications for Pan-STARRS1
• A Comparison of Weak Lensing Measurements From Ground- and Space-Based Facilities
• The Faint End Slopes Of Galaxy Luminosity Functions In The COSMOS 2-Square Degree Field
• High resolution science with high redshift galaxies
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• Optical Selection of Faint AGN in the COSMOS Field
• Evolution of the Frequency of Luminous (\geq L_V*) Close Galaxy Pairs at z < 1.2 in the COSMOS Field