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J/ApJ/690/1236      COSMOS photometric redshift catalog       (Ilbert+, 2009)

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., Fevre O.L., Lilly S., Looper D., Maier C., Mainieri V., Mellier Y., Mignoli M., Murayama T., Pello R., Peng Y., Perez-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. <Astrophys. J., 690, 1236-1249 (2009)> =2009ApJ...690.1236I (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galaxy catalogs ; Redshifts ; Photometry Keywords: galaxies: distances and redshifts - galaxies: evolution - galaxies: formation Abstract: 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. Description: 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. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file cosmoszp.dat 414 385065 COSMOS photometric redshift catalog, Version 1.5, April, 05 2008 - Magnitude-limited (I<25)
See also: II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007) VII/265 : COSMOS Morphological Catalog (V1.1) (Tasca+ 2009) Byte-by-byte Description of file: cosmoszp.dat
Bytes Format Units Label Explanations
1- 7 I7 --- Name [26310/1993775] Name (Id) 9- 11 I3 --- Tile [13/117] Tile (tile) 13- 22 F10.6 deg RAdeg Right ascension (J2000) (alpha) 24- 31 F8.6 deg DEdeg Declination (J2000) (delta) 33- 40 F8.6 --- zpbest ? Best photometric redshift (zp_best) (1) 42- 45 I4 --- zpType [0/2]? Redshift type (type) (2) 47- 54 F8.6 --- zpgal [0/6]? Photo-z measured using the galaxy templates (zp_gal) (3) 56- 63 F8.6 --- l68zpgal ? Lower limit, 68% confidence level on zpgal (zl68_gal) 65- 72 F8.6 --- u68zpgql ? Upper limit, 68% confidence level on zpgal (zu68_gal) 74- 81 F8.6 --- l99zpgal ? Lower limit, 99% confidence level on zpgal (zl99_gal) 83- 90 F8.6 --- u99zpgal ? Upper limit, 99% confidence level on zpgal (zu99_gal) 92-102 F11.6 --- chigal ? Reduced chi2 (null if less than 3 filters) (chi_gal) 104-107 I4 --- modgal [0/47]? Best fit template (mod_gal) (4) 109-116 F8.6 --- E(B-V) ? additional extinction (ebv) (5) 118-125 F8.6 --- zpsec [0/6]? Second photo-z solution if a second peak is detected in the PDFz (null if not detected) (zp_sec) 127-143 F17.6 --- chisec ? Reduced chi2 for the second photo-z solution (use only if zpsec>0) (chi_sec) 145-148 I4 --- modsec [0/47]? Template for the second photo-z solution (use only if zpsec>0) (mod_sec) 150-157 F8.6 --- E(B-V)sec ? Additional extinction for the second photo-z solution (use only if zp_sec>0) (ebv_sec) 159-162 I4 --- modstar [-119/0]? Model for the star library (mod_star) (6) 164-174 F11.6 --- chistar ? Reduced chi2 (chi_star) 176-184 F9.6 mag Umag ? CFHT u* aperture magnitude (3" aperture) (Umag) 186-194 F9.6 mag Bmag ? Subaru B aperture magnitude (3" aperture) (Bmag) 196-204 F9.6 mag Vmag ? Subaru V aperture magnitude (3" aperture) (Vmag) 206-214 F9.6 mag Gmag ? Subaru g+ aperture magnitude (3" aperture) (Gmag) 216-224 F9.6 mag Rmag ? Subaru r+ aperture magnitude (3" aperture) (Rmag) 226-234 F9.6 mag Imag ? Subaru i+ aperture magnitude (3" aperture) (Imag) 236-244 F9.6 mag Zmag ? Subaru z+ aperture magnitude (3" aperture) (Zmag) 246-254 F9.6 mag ICmag ? CFHT i' aperture magnitude (3" aperture) (ICmag) 256-264 F9.6 mag Jmag ? UKIRT J aperture magnitude (3" aperture) (Jmag) 266-274 F9.6 mag Kmag ? CFHT K aperture magnitude (3" aperture) (Kmag) 276-283 F8.6 mag e_Umag ? rms uncertainty on Umag (eU) 285-292 F8.6 mag e_Bmag ? rms uncertainty on Bmag (eB) 294-301 F8.6 mag e_Vmag ? rms uncertainty on Vmag (eV) 303-310 F8.6 mag e_Gmag ? rms uncertainty on Gmag (eG) 312-319 F8.6 mag e_Rmag ? rms uncertainty on Rmag (eI) 321-328 F8.6 mag e_Imag ? rms uncertainty on Imag (eZ) 330-337 F8.6 mag e_Zmag ? rms uncertainty on Xmag (eZ) 339-346 F8.6 mag e_ICmag ? rms uncertainty on ICmag (eIC) 348-355 F8.6 mag e_Jmag ? rms uncertainty on Jmag (eJ) 357-364 F8.6 mag e_Kmag ? rms uncertainty on Kmag (eK) 366 I1 --- f_Bmag [0/9] Photometric flag, mask in the B band, 0 good (flagB) 368 I1 --- f_Vmag [0/9] Photometric flag, mask in the V band, 0 good (flagV) 370 I1 --- f_Imag [0/9] Photometric flag, mask in the I band, 0 good (flagi) 372 I1 --- f_Zmag [0/9] Photometric flag, mask in the Z band, 0 good (flagz) 374 I1 --- f_D [0] Photometric flag, mask in the deep area, 0 good (flagD) 376-377 I2 --- NbFilt [0/34] Number of filters used in the photo-z fitting (NbFilt) 379-388 F10.6 mag imag ?=-99 Auto magnitude in the i band (I_auto) 390-399 F10.6 mag ioffset ?=-99 Offset to transform aperture magnitude into auto (auto_offset) 401-402 I2 --- q_ioffset [-1/2] Quality flag in the offset 404-414 F11.6 mag VMAG Absolute magnitude in the V(Subaru) band (valid only for galaxies) (MV)
Note (1): Best photometric redshift : z = zgal if galaxy (column 7) z = 0 if star z = 9.99 if Xray (Use the photo-z values from Salvato et al. 2009ApJ...690.1250S, released separately) Note (2): Redshift type as follows: 0 = galaxy 1 = star 2 = Xray source null = masked area Note (3): Best fit obtained with the galaxy templates Note (4): Best fit template: 1 -> 8 Ell-S0 9 ->15 Sa-Sc 16 ->19 Sd-Sdm from Polletta et al. (2007, Cat. J/ApJ/663/81) ≥20 from Bruzual & Charlot (2003MNRAS.344.1000B) Note (5): Additional extinction: Prevot et al. (1984A&A...132..389P) for templates ≤24 Calzetti et al. (2000ApJ...533..682C) for template >24 Note (6): Best fit obtained with the star templates
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(End) Patricia Vannier [CDS] 08-Mar-2017
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