McCracken, H. J.
Sanders, D. B.
Le Floc'h, E.
Caputi, K. I.
Carollo, C. M.
de la Torre, S.
de Ravel, L.
Le Borgne, J. F.
Le Brun, V.
Fevre, O. L.
- Data Collection
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 ([OII], 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=zs-zp) indicates a dispersion of σΔz/(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 σΔz/(1+zs)=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 (σΔz/(1+zs)=0.006 at i+AB∼24). The redshift distribution of large magnitude-selected samples is derived and the median redshift is found to range from zm= 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. Compared with the previous optical/NIR catalog (Capak et al., 2007ApJS..172...99C, Cat. II/284), the new photometry implements 14 new medium/narrowband data from the Subaru Telescope, deep ground-based NIR data (J and K bands), and Spitzer-IRAC data. The spectroscopic sample used to calibrate/test the photo-z is 10 times larger at i+AB<22.5 than that of Mobasher et al. (2007ApJS..172..117M). The spectroscopic sample is supplemented with faint IR selected sources and a deep, faint spectroscopic sample at z>1.5. Hereafter, we detail the photometric and spectroscopic data used to measure the photo-z. Fluxes are measured in 30 bands from data taken on the Subaru (4200-9000Åg), CFHT (3900-21500Å), UKIRT (12500Å), Spitzer (3.6-8um), and GALEX (1500.2300Å) telescopes. We refer to P. Capak et al. (2008, in preparation) for a complete description of the observations, data reduction, and the photometry catalog. Photometric catalogue from P. Capak, Photo-z catalogue from O. Ilbert, PIs of the photometric data: D.B. Sanders, N. Scoville, Y. Tanigushi / Data reducers: H. Aussel, P. Capak, H. McCracken, M. Salvato, S. Sasaki,D. Thompson, O. Ilbert, J. Kartaltepe, E. Le Floc'h, D. Looper, D.B. Sanders, N. Scoville / Spectroscopic redshifts for validation from the zCOSMOS team (PI S. Lilly), from J. Kartaltepe and from P. Capak / Identification of the Xray sources in the optical catalogue M. Brusa, G. Hasinger and the COSMOS/XMM team Show more
PublisherCDS Centré de Données astronomiques des Strasbourg
SubjectSurveys; Galaxy catalogs; Redshifts; Photometry; Galaxies: distances and redshifts; Galaxies: evolution; Galaxies: formation
Organisational unit03612 - Carollo, Marcella
Related publications and datasets
Is supplement to: http://hdl.handle.net/20.500.11850/14991
NotesVizieR Online Data Catalog: J/ApJ/690/1236
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