Cosmos Photometric Redshifts with 30-Bands for 2-deg2

Ilbert, O.; Capak, P.; Salvato, M.; Aussel, H.; Mccracken, H. J.; Sanders, D. B.; Scoville, N.; Kartaltepe, J.; Arnouts, S.; Le Floc'h, E.; Mobasher, B.; Taniguchi, Y.; Lamareille, F.; Leauthaud, A.; Sasaki, S.; Thompson, D.; Zamojski, M.; Zamorani, G.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Brusa, Marcella; Caputi, K. I.; Carollo, C. M.; Contini, T.; Cook, R.; Coppa, G.; Cucciati, Olga; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Hasinger, G.; Iovino, A.; Kampczyk, P.; Kneib, J. P.; Knobel, C.; Kovac, K.; Le Borgne, J. F.; Le Brun, V.; Fèvre O., Le; Lilly, S.; Looper, D.; Maier, C.; Mainieri, V.; Mellier, Y.; Mignoli, M.; Murayama, T.; Pellò, R.; Peng, Y.; Pérez Montero, E.; Renzini, A.; Ricciardelli, E.; Schiminovich, D.; Scodeggio, M.; Shioya, Y.; Silverman, J.; Surace, J.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Zucca, E.

doi:10.1088/0004-637X/690/2/1236

We present accurate photometric redshifts (photo-z) in the 2-deg2 COSMOS field. The redshifts are computed with 30 broad, intermediate, and narrowbands covering the UV (Galaxy Evolution Explorer), visible near-IR (NIR; Subaru, Canada-France-Hawaii Telescope (CFHT), United Kingdom Infrared Telescope, and National Optical Astronomy Observatory), and mid-IR (Spitzer/IRAC). A χ2 template-fitting method (Le Phare) was used and calibrated with large spectroscopic samples from the Very Large Telescope Visible Multi-Object Spectrograph and the Keck Deep Extragalactic Imaging Multi-Object Spectrograph. We develop and implement a new method which accounts for the contributions from emission lines ([O II], Hβ, Hα, and Lyα) 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., Δz = z s - z p) indicates a dispersion of σ_{Δ z/(1+z_s)}=0.007 at i + AB < 22.5, a factor of 2-6 times more accurate than earlier photo-z in the COSMOS, CFHT Legacy Survey, and the Classifying Object by Medium-Band Observations-17 survey fields. At fainter magnitudes i + AB < 24 and z < 1.25, the accuracy is σ_{Δ z/(1+z_s)}=0.012. The deep NIR and Infrared Array Camera coverage enables the photo-z to be extended to z ~ 2, albeit with a lower accuracy (σ_{Δ z/(1+z_s)}=0.06 at i + AB ~ 24). The redshift distribution of large magnitude-selected samples is derived and the median redshift is found to range from z m = 0.66 at 22 < i + AB < 22.5 to z m = 1.06 at 24.5 < i + AB < 25. At i + AB < 26.0, the multiwavelength COSMOS catalog includes approximately 607,617 objects. The COSMOS-30 photo-z enables the full exploitation of this survey for studies of galaxy and large-scale structure evolution at high redshift.

Cosmos Photometric Redshifts with 30-Bands for 2-deg2 / Ilbert O.; Capak P.; Salvato M.; Aussel H.; McCracken H. J.; Sanders D. B.; Scoville N.; Kartaltepe J.; Arnouts S.; Le Floc'h E.; Mobasher B.; Taniguchi Y.; Lamareille F.; Leauthaud A.; Sasaki S.; Thompson D.; Zamojski M.; Zamorani G.; Bardelli S.; Bolzonella M.; Bongiorno A.; Brusa M.; Caputi K. I.; Carollo C. M.; Contini T.; Cook R.; Coppa G.; Cucciati O.; de la Torre S.; de Ravel L.; Franzetti P.; Garilli B.; Hasinger G.; Iovino A.; Kampczyk P.; Kneib J.-P.; Knobel C.; Kovac K.; Le Borgne J. F.; Le Brun V.; Fèvre O. Le; Lilly S.; Looper D.; Maier C.; Mainieri V.; Mellier Y.; Mignoli M.; Murayama T.; Pellò R.; Peng Y.; Pérez-Montero E.; Renzini A.; Ricciardelli E.; Schiminovich D.; Scodeggio M.; Shioya Y.; Silverman J.; Surace J.; Tanaka M.; Tasca L.; Tresse L.; Vergani D.; Zucca E.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 690:(2009), pp. 1236-1249. [10.1088/0004-637X/690/2/1236]