2008/09/11 by O. Ilbert, P. Capak, M. Salvato +64 · 12 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Infrared #Photometric redshift #Redshift #Spectral energy distribution #Spectrograph #Telescope #Very Large Telescope #astro-ph
paper · pdf · doi:10.1088/0004-637x/690/2/1236
published as Astrophys.J.690:1236-1249,2009 · 21 pages, 14 figures, and 3 tables ; accepted for publication in ApJ
arxiv created 2008/09/11 · openalex publication_date 2008/12/08 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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 χ 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 ], 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., Δ z = z s − z p ) indicates a dispersion of 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 . The deep NIR and Infrared Array Camera coverage enables the photo-z to be extended to z ∼ 2, albeit with a lower accuracy ( 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.