We present accurate photometric redshifts (photo-z) in the 2-deg(2) 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 chi(2) 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], H beta, H alpha, and Ly alpha) 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 = z(s) - z(p)) indicates a dispersion of sigma(Delta z)/((1+zs)) = 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 sigma(Delta z/(1+zs)) = 0.012. The deep NIR and Infrared Array Camera coverage enables the photo-z to be extended to z similar to 2, albeit with a lower accuracy (sigma(Delta z/(1+zs)) = 0.06 at i(AB)(+) similar to 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 zm = 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.; Floc'H, E. Le; 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. - 690:2(2009), pp. 1236-1249. [10.1088/0004-637X/690/2/1236]

COSMOS PHOTOMETRIC REDSHIFTS WITH 30-BANDS FOR 2-deg2

Coppa, G.;
2009

Abstract

We present accurate photometric redshifts (photo-z) in the 2-deg(2) 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 chi(2) 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], H beta, H alpha, and Ly alpha) 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 = z(s) - z(p)) indicates a dispersion of sigma(Delta z)/((1+zs)) = 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 sigma(Delta z/(1+zs)) = 0.012. The deep NIR and Infrared Array Camera coverage enables the photo-z to be extended to z similar to 2, albeit with a lower accuracy (sigma(Delta z/(1+zs)) = 0.06 at i(AB)(+) similar to 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 zm = 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.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11696/71445
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