Estimating the redshift distribution of photometric galaxy samples – II. Applications and tests of a new method

In Lima et al. (2008) we presented a new method for estimating the redshift distribution, N(z), of a photometric galaxy sample, using photometric observables and weighted sampling from a spectroscopic subsample of the data. In this paper, we extend this method and explore various applications of it, using both simulations of and real data from the SDSS. In addition to estimating the redshift distribution for an entire sample, the weighting method enables accurate estimates of the redshift probability distribution, p(z), for each galaxy in a photometric sample. Use of p(z) in cosmological analyses can substantially reduce biases associated with traditional photometric redshifts, in which a single redshift estimate is associated with each galaxy. The weighting procedure also naturally indicates which galaxies in the photometric sample are expected to have accurate redshift estimates, namely those that lie in regions of photometric-observable space that are well sampled by the spectroscopic subsample. In addition to providing a method that has some advantages over standard photo-z estimates, the weights method can also be used in conjunction with photo-z estimates, e.g., by providing improved estimation of N(z) via deconvolution of N(zphot) and improved estimates of photo-z scatter and bias.

[1]  B. Yanny,et al.  The Sloan Digital Sky Survey monitor telescope pipeline , 2006 .

[2]  J. Frieman,et al.  Photometric Redshift Error Estimators , 2007, 0711.0962.

[3]  A. Mazure,et al.  The VIMOS VLT deep survey , 2001, 0903.0271.

[4]  Wayne Hu,et al.  Effects of Photometric Redshift Uncertainties on Weak-Lensing Tomography , 2005 .

[5]  S. J. Lilly,et al.  The Canada-France Redshift Survey. I. Introduction to the Survey, Photometric Catalogs, and Surface Brightness Selection Effects , 1995 .

[6]  S. Maddox,et al.  zCOSMOS: A Large VLT/VIMOS Redshift Survey Covering 0 < z < 3 in the COSMOS Field , 2006, astro-ph/0612291.

[7]  Hu Zhan,et al.  Cosmic tomographies: baryon acoustic oscillations and weak lensing , 2006 .

[8]  R. Lupton,et al.  Astrometric Calibration of the Sloan Digital Sky Survey , 2002, astro-ph/0211375.

[9]  J. Gunn,et al.  A Photometricity and Extinction Monitor at the Apache Point Observatory , 2001, astro-ph/0106511.

[10]  John E. Davis,et al.  Sloan Digital Sky Survey: Early Data Release , 2002 .

[11]  A. Iserles.  Numerical recipes in C—the art of scientific computing , by W. H. Press, B. P. Flannery, S. A. Teukolsky and W. T. Vetterling. Pp 735. £27·50. 1988. ISBN 0-521-35465-X (Cambridge University Press) , 1989, The Mathematical Gazette.

[12]  Alexander S. Szalay,et al.  Calibrating photometric redshifts of luminous red galaxies , 2005 .

[13]  P. Hall,et al.  The CNOC2 Field Galaxy Redshift Survey. I. The Survey and the Catalog for the Patch CNOC 0223+00 , 2000, astro-ph/0004026.

[14]  J. Newman,et al.  The Team Keck Treasury Redshift Survey of the GOODS-North Field , 2004, astro-ph/0401353.

[15]  S. L. Morris,et al.  The CNOC2 Field Galaxy Luminosity Function. I. A Description of Luminosity Function Evolution , 1999 .

[16]  William H. Press,et al.  Numerical recipes in C. The art of scientific computing , 1987 .

[17]  R. J. Brunner,et al.  The 2dF-SDSS LRG and QSO (2SLAQ) luminous red galaxy survey , 2006, astro-ph/0607631.

[18]  E. al.,et al.  The Sloan Digital Sky Survey: Technical summary , 2000, astro-ph/0006396.

[19]  H. Payne,et al.  Astronomical Data Analysis Software and Systems X , 2001 .

[20]  Walter A. Siegmund,et al.  The 2.5 m Telescope of the Sloan Digital Sky Survey , 2006, astro-ph/0602326.

[21]  L. Knox,et al.  Baryon Oscillations and Consistency Tests for Photometrically Determined Redshifts of Very Faint Galaxies , 2005, astro-ph/0509260.

[22]  I. Smail,et al.  The All-Wavelength Extended Groth Strip International Survey (AEGIS) Data Sets , 2006, astro-ph/0607355.

[23]  M. Fukugita,et al.  The Sloan Digital Sky Survey Photometric System , 1996 .

[24]  Sarah Bridle,et al.  Cosmology with photometric redshift surveys , 2004 .

[25]  Donald E. Knuth,et al.  The TeXbook , 1984 .

[26]  Redshift Accuracy Requirements for Future Supernova and Number Count Surveys , 2004, astro-ph/0402002.

[27]  池内 健二,et al.  Document preparation system , 2006 .

[28]  THE DEEP GROTH STRIP GALAXY REDSHIFT SURVEY. III. REDSHIFT CATALOG AND PROPERTIES OF GALAXIES , 2004, astro-ph/0411128.

[29]  D. Weedman,et al.  Colors and magnitudes predicted for high redshift galaxies , 1980 .

[30]  S. J. Lilly,et al.  The Canada-France Deep Fields Survey. III. Photometric Redshift Distribution to IAB = 24 , 2003, astro-ph/0310038.

[31]  Mamoru Doi,et al.  Estimating Fixed-Frame Galaxy Magnitudes in the Sloan Digital Sky Survey , 2002, astro-ph/0205243.

[32]  William H. Press,et al.  The Art of Scientific Computing Second Edition , 1998 .

[33]  Masahiro Takada,et al.  Systematic errors in future weak-lensing surveys: requirements and prospects for self-calibration , 2006 .

[34]  Huan Lin,et al.  A Galaxy Photometric Redshift Catalog for the Sloan Digital Sky Survey Data Release 6 , 2007, 0708.0030.

[35]  S. Charlot,et al.  Spectral evolution of stellar populations using isochrone synthesis , 1993 .

[36]  Ofer Lahav,et al.  ANNz: Estimating Photometric Redshifts Using Artificial Neural Networks , 2004 .

[37]  S. Roweis,et al.  An Improved Photometric Calibration of the Sloan Digital Sky Survey Imaging Data , 2007, astro-ph/0703454.

[38]  M. Lima,et al.  Photometric Redshift Requirements for Self-Calibration of Cluster Dark Energy Studies , 2007, 0709.2871.

[39]  Alan Uomoto,et al.  The [CLC][ITAL]u[/ITAL][/CLC][arcmin]′[CLC][ITAL]g[/ITAL][/CLC][arcmin]′[CLC][ITAL]r[/ITAL][/CLC][arcmin]′[CLC][ITAL]i[/ITAL][/CLC][arcmin]′[CLC][ITAL]z[/ITAL][/CLC][arcmin]′ Standard-Star System , 2002 .