Transcript BPZ
Bayesian Photometric Redshifts (BPZ) Narciso Benítez1,2 (2000) Narciso Benítez1,2 et al. (2004) Dan Coe1,2,3 et al. (2006) Johns Hopkins University1 Instituto de Astrofísica de Andalucía2 JPL/Caltech3 Science Team Photo-z Methods Spectral Energy Distribution (SED) Template Fitting Empirical Training Set (Neural Networks) BPZ v1.99b Benítez ‘00, ‘04 Coe ‘06 Bruzual & Charlot ‘03 Kinney ‘96 Coleman, Wu, Weedman ‘80 Normally interpolate 2 between adjacent templates http://adcam.pha.jhu.edu/~txitxo/ Spectral Energy Distribution (SED) templates recalibrated with real photometry Flux SED template fit Wavelength Bayesian use of priors without prior Probability prior: I = 26 with prior with prior Output: Redshift Benítez00 Poorness of Fit Poorest fits yield most accurate redshifts! Benítez00 Redshift Inaccuracy (photo-z vs. spec-z) 2 = 4.27 2mod = 0.03 2 = 0.11 Flux 2mod = 0.19 Wavelength PHAT GOODS BPZ results (training set) Important to plot error bars and goodness-of-fit PHAT GOODS BPZ results (training set) Single-peaked P(z) [ODDS 0.95] no error bars plotted Most GOODS objects have good photometry ACS ground IRAC …but some are bad ACS ground IRAC …some are ugly ACS ground IRAC Robust photo-z’s require Robust photometry QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. One of the best methods (even if Peter doesn’t like it ;) PSF-corrected aperture-matched photometry What is the best method? PHOTEST Photometry Testing PSF Degradation vs. Model Fitting Magnitude Uncertainties Zeropoint Calibration Object Detection & Deblending … Sounds like a job for a new group Let’s meet in Greece 2009 UDF NICMOS fluxes too low Objects w/ spec-z NICMOS flux recalibration Comprehensive Segmentation Map Forced into SExtractor Wish List (Goals for PHAT?) Improve SED library more galaxy types broader wavelength coverage SED uncertainties derived from population synthesis models?? Improve Priors using UDF, surveys Optimal Filter Choice for a given amount of observing time Benítez et al. (2008) A&A submitted 4 - 5 filters is sub-optimal ! addition of near-IR helps somewhat > 8 filters performs much better Filters tested = const contiguous overlapping Photo-z completeness Best is > 8 overlapping filters Depth to which 80% of objects have ODDS ≥ 0.99 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Photo-z accuracy for ODDS ≥ 0.99 objects Best is many non-overlapping (contiguous) filters ALHAMBRA Survey (Moles08) 20 medium-band (310Å wide) filters 3500 - 9700Å, supplemented by JHKs lab including CCD, atmosphere, mirror reflectivity ALHAMBRA Survey 1.5’ x 1.5’ 14-filter color image to cover 4+ sq deg QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 8,000 - 10,000 sq deg z < 0.9 - 1.0 4 - 5 years 6 sq deg camera new 2-3m telescope to be built in Aragon, Spain PAU Survey: 40 100Å-wide filters (~4000-8000Å) + SDSS u & z QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. PAU Survey: z/(1+z) < 0.0015 for z < 0.4, L > L*, I < 23 LRGs QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. PAU Survey: BAO cosmological constraints PAU Survey: relative w constraints