Photometric Redshifts of Galaxies in COSMOS

By B. Mobasher, P. Capak, N. Scoville, T. Dahlén, Mara Salvato, H. Aussel, D. Thompson, Robert Feldmann, L. Tasca, O. LeFèvre and 19 more. 2006

137 citations recorded by the source corpus.

We present photometric redshifts for the COSMOS survey derived from a new code, optimized to yield accurate and reliable redshifts and spectral types of galaxies down to faint magnitudes and redshifts out to z ~ 1.2. The technique uses χ2 template fitting, combined with luminosity function priors and with the option to estimate the internal extinction [or E(B - V)]. The median most probable redshift, best-fit spectral type and reddening, absolute magnitude, and stellar mass are derived in addition to the full redshift probability distributions. Using simulations with sampling and noise 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. We find from the simulations that the ratio of derived 95% confidence interval in the χ2 probability distribution to the estimated photometric redshift (D95) can be used to identify and exclude the catastrophic failures in the photometric redshift estimates. To evaluate the reliability of the photometric redshifts, 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. The rms scatter between the estimated photometric redshifts and known spectroscopic redshifts is σ(Δ(z)) = 0.031, where Δ(z) = (zphot - zspec)/(1 + zspec) with a small fraction of outliers (<2.5%) [outliers are defined as objects with Δ(z) > 3σ(Δ(z)), where σ(Δ(z)) is the rms scatter in Δ(z)]. We also find good agreement [σ(Δ(z)) = 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).

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/8f37a3416b6a468710db8778859a1d4e08a54206

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Citations in the corpus

The dependence of star formation activity on environment and stellar mass at z∼ 1 from the HiZELS-Hα survey (2010, methodology): “Comparison between the determined stellar masses and those from Mobasher et al. (2007) and Cirasuolo et al. (in prep.).”
Evolution of the Frequency of Luminous (≥LV⋆) Close Galaxy Pairs at z < 1.2 in the COSMOS Field (2007, methodology): “To estimate the mass of each galaxy in the COSMOS photometric catalog, Mobasher et al. (2007) used a relation between M/LV and rest-frame (B − V )0 colors given by Bell et al. (2005).”
COSMOS: Hubble Space Telescope Observations (2006, background): “These catalogs and the derived photometric redshifts (Mobasher et al. 2007) are presented and described in detail elsewhere (Koekemoer et al. 2007; Capak et al. 2007a; Leauthaud et al. 2007).”
A new measurement of the evolving near-infrared galaxy luminosity function out to z≃ 4: a continuing challenge to theoretical models of galaxy formation (2008, result): “This accuracy is comparable to the best available from other surveys such as GOODS and COSMOS (Caputi et al. 2006; Grazian et al. 2006; Mobasher et al. 2007).”
Deep GALEX Imaging of the COSMOS HST Field: A First Look at the Morphology of z ~ 0.7 Star-forming Galaxies (2007, methodology): “We further performed SED fitting of this multi-band data and calculated photometric redshifts for galaxies with i < 25 mag (AB) (Mobasher et al. 2007).”
The structures of distant galaxies – III. The merger history of over 20 000 massive galaxies at z < 1.2 (2008, methodology): “The photometric data in which these quantities are derived include optical data in the u∗ band from the CFHT, BgV riz imaging from the SuprimeCam on Subaru, i− imaging from CHFT and KS imaging from FLAMINGOS taken at CTIO and Kitt Peak (Mobasher et al. 2007).”
Photometric redshifts for the CFHTLS T0004 deep and wide fields (2008, background): “Figure 3 shows the comparison between photometric and VVDS spectroscopic redshifts for the D1 field; zCOSMOS for the D2 field and DEEP2 for the D3 field.”
The XMM-Newton Wide-Field Survey in the COSMOS Field: Statistical Properties of Clusters of Galaxies (2006, methodology): “The combination of depth and bands allows us to produce an i-band based photo-z catalog with a 1σ uncertainty of the redshift estimate of 0.027(1 + z) for galaxies with iAB < 25 (Mobasher et al. 2007) obtained without the luminosity prior.”
HiZELS: a high-redshift survey of Hα emitters – I. The cosmic star formation rate and clustering at z= 2.23 (2008, methodology): “Identification of lower redshift interlopers will become easier when more accurate photometric redshifts are available for COSMOS (Mobasher et al. 2007 & private communication).”
Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS (2009, methodology): “Furthermore, Massey et al. (2007c) employ earlier photo-zs based on fewer bands (Mobasher et al. 2007).”
PHAT: PHoto-z Accuracy Testing (2010, background): “This template correction step has been shown to be a crucial ingredient in decreasing the bias, the scatter, and the number of outliers in the redshift estimation (e.g. Feldmann et al. 2006; Mobasher et al. 2007).”
A universal ultraviolet–optical colour–colour–magnitude relation of galaxies★ (2011, background): “Mobasher et al. (2007) analyse the performance of different photometric redshift codes on a data set that comprises 16 photometric points for every SED in question.”
COSBO: The MAMBO 1.2 Millimeter Imaging Survey of the COSMOS Field (2007, methodology): “The X-ray counterparts for these two sources were identified with ID 366459 and ID 286874 from the photoredshift catalog (Mobasher et al. 2007).”
The star formation history of K-selected galaxies (2008, result): “This accuracy is comparable to the best available from other surveys such as GOODS and COSMOS (Caputi et al. 2006a; Grazian et al. 2006; Mobasher et al. 2007).”
ACTIVE GALACTIC NUCLEUS HOST GALAXY MORPHOLOGIES IN COSMOS (2009, methodology): “To complement the morphological analysis, we use the COSMOS photometric redshift catalog (Mobasher et al. 2007; Capak et al. 2007) as a filter to search for near neighbors to the AGNs.”
Weak Gravitational Lensing with COSMOS: Galaxy Selection and Shape Measurements (2007, methodology): “The imaging quality and unprecedented area of the COSMOS ACS/WFC data, combinedwith extensive follow-up observations at other wavelengths (Scoville et al. 2007; Koekemoer 2007) to provide accurate photometric redshifts (Mobasher et al. 2007), make COSMOS a unique data set for weak-lensing studies.”
Photometric redshifts in the SWIRE Survey (2008, methodology): “The outlier performance is significantly better than Wolf et al (2004), Ilbert et al (2006), Mobasher et al (2007) , which we attribute to the use of the SWIRE 3.6 and 4.5 µm bands.”