COSMOS Photometric Redshifts with 30-bands for 2-deg2
Abstract
We present accurate photometric redshifts in the 2-deg2 COSMOS field. The redshifts are computed with 30 broad, intermediate, and narrow bands covering the UV (GALEX), Visible-NIR (Subaru, CFHT, UKIRT and NOAO) and mid-IR (Spitzer/IRAC). A chi2 template-fitting method (Le Phare) was used and calibrated with large spectroscopic samples from VLT-VIMOS and Keck-DEIMOS. We develop and implement a new method which accounts for the contributions from emission lines (OII, Hbeta, Halpha and Ly) to the spectral energy distributions (SEDs). The treatment of emission lines improves the photo-z accuracy by a factor of 2.5. Comparison of the derived photo-z with 4148 spectroscopic redshifts (i.e. Delta z = zs - zp) indicates a dispersion of sigma_{Delta z/(1+zs)}=0.007 at i<22.5, a factor of 2-6 times more accurate than earlier photo-z in the COSMOS, CFHTLS and COMBO-17 survey fields. At fainter magnitudes i<24 and z<1.25, the accuracy is sigma_{Delta z/(1+zs)}=0.012. The deep NIR and IRAC coverage enables the photo-z to be extended to z~2 albeit with a lower accuracy (sigma_{Delta z/(1+zs)}=0.06 at i~24). The redshift distribution of large magnitude-selected samples is derived and the median redshift is found to range from z=0.66 at 22<i<22.5 to z=1.06 at 24.5<i<25. At i<26.0, the multi-wavelength COSMOS catalog includes approximately 607,617 objects. The COSMOS-30 photo-z enable the full exploitation of this survey for studies of galaxy and large scale structure evolution at high redshift.
Keywords
Cite
@article{arxiv.0809.2101,
title = {COSMOS Photometric Redshifts with 30-bands for 2-deg2},
author = {O. Ilbert and P. Capak and M. Salvato and H. Aussel and H. J. McCracken and D. B. Sanders and N. Scoville and J. Kartaltepe and S. Arnouts and E. Le Floc'h and B. Mobasher and Y. Taniguchi and F. Lamareille and A. Leauthaud and S. Sasaki and D. Thompson and M. Zamojski and G. Zamorani and S. Bardelli and M. Bolzonella and A. Bongiorno and M. Brusa and K. I. Caputi and C. M. Carollo and T. Contini and R. Cook and G. Coppa and O. Cucciati and S. de la Torre and L. de Ravel and P. Franzetti and B. Garilli and G. Hasinger and A. Iovino and P. Kampczyk and J. -P. Kneib and C. Knobel and K. Kovac and J. F. Le Borgne and V. Le Brun and O. Le Fevre and S. Lilly and D. Looper and C. Maier and V. Mainieri and Y. Mellier and M. Mignoli and T. Murayama and R. Pello and Y. Peng and E. Perez-Montero and A. Renzini and E. Ricciardelli and D. Schiminovich and M. Scodeggio and Y. Shioya and J. Silverman and J. Surace and M. Tanaka and L. Tasca and L. Tresse and D. Vergani and E. Zucca},
journal= {arXiv preprint arXiv:0809.2101},
year = {2008}
}
Comments
21 pages, 14 figures, and 3 tables ; accepted for publication in ApJ