A CRITICAL ASSESSMENT OF PHOTOMETRIC REDSHIFT METHODS: A CANDELS INVESTIGATION

By T. Dahlén, B. Mobasher, S. Faber, H. Ferguson, G. Barro, S. Finkelstein, K. Finlator, A. Fontana, R. Gruetzbauch, S. Johnson and 28 more. 2013

250 citations recorded by the source corpus.

We present results from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) photometric redshift methods investigation. In this investigation, the results from 11 participants, each using a different combination of photometric redshift code, template spectral energy distributions (SEDs), and priors, are used to examine the properties of photometric redshifts applied to deep fields with broadband multi-wavelength coverage. The photometry used includes U-band through mid-infrared filters and was derived using the TFIT method. Comparing the results, we find that there is no particular code or set of template SEDs that results in significantly better photometric redshifts compared to others. However, we find that codes producing the lowest scatter and outlier fraction utilize a training sample to optimize photometric redshifts by adding zero-point offsets, template adjusting, or adding extra smoothing errors. These results therefore stress the importance of the training procedure. We find a strong dependence of the photometric redshift accuracy on the signal-to-noise ratio of the photometry. On the other hand, we find a weak dependence of the photometric redshift scatter with redshift and galaxy color. We find that most photometric redshift codes quote redshift errors (e.g., 68% confidence intervals) that are too small compared to that expected from the spectroscopic control sample. We find that all codes show a statistically significant bias in the photometric redshifts. However, the bias is in all cases smaller than the scatter; the latter therefore dominates the errors. Finally, we find that combining results from multiple codes significantly decreases the photometric redshift scatter and outlier fraction. We discuss different ways of combining data to produce accurate photometric redshifts and error estimates.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/989f4079cff2428d713a5064bbbdf1125f2d8794

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Citations in the corpus

The Evolution of Galaxy Structure Over Cosmic Time (2014, methodology): “This allowed redshifts to be measured for most galaxies using photometry through so-called photometric redshifts (e.g., Dahlen et al. (2013) for a recent discussion of the use of this method).”
AN ALMA SURVEY OF SUBMILLIMETER GALAXIES IN THE EXTENDED CHANDRA DEEP FIELD SOUTH: THE REDSHIFT DISTRIBUTION AND EVOLUTION OF SUBMILLIMETER GALAXIES (2013, methodology): “We find the photometric redshifts derived by EAZY are comparable with those from HYPERZ, with a median ∆z / 1 + zspec = 0.020 ± 0.006; consistent with Dahlen et al. (2013) who find comparable performance between photometric redshift estimation codes. we find the failure rate for the 1077 sources at…”
THE EVOLUTION OF THE GALAXY REST-FRAME ULTRAVIOLET LUMINOSITY FUNCTION OVER THE FIRST TWO BILLION YEARS (2014, background): “In comparison, when defining outliers in the same way, we find that the published CANDELS team photometric redshift catalog has 13 outliers out of 174 total spectroscopic redshifts, for a somewhat higher outlier fraction of 7.5% (Dahlen et al. 2013).”
Modelling and interpreting spectral energy distributions of galaxies with BEAGLE (2016, methodology): “In fact, redshift is considered to be the most robust quantity that can be constrained from broad-band photometric data, while determinations of galaxy physical parameters are expected to be more model-dependent (e.g. Dahlen et al. 2013; Mobasher et al. 2015).”
The mass evolution of the first galaxies: stellar mass functions and star formation rates at 4 < z < 7 in the CANDELS GOODS-South field (2014, background): “Dahlen et al. (2013) have recently shown that by combining the results from multiple photometric redshift codes, the scatter and outlier fraction in photometric redshifts can be significantly reduced compared to the results of any single code.”
Photometric redshift analysis in the Dark Energy Survey Science Verification data (2014, methodology): “Similarly, Dahlen et al. (2013) compares 11 codes over real data in 14 bands, including also some HST data.”
TYPE Ia SUPERNOVA RATE MEASUREMENTS TO REDSHIFT 2.5 FROM CANDELS: SEARCHING FOR PROMPT EXPLOSIONS IN THE EARLY UNIVERSE (2014, methodology): “The photo-z estimates were derived from template fitting to the observed spectral energy distribution (SED) of each SN host galaxy (Dahlen et al. 2013).”
The COSMOS2015 galaxy stellar mass function . Thirteen billion years of stellar mass assembly in ten snapshots (2017, methodology): “To include the uncertainty on photometric redshift and obtain PDF(M|z), G15 multiply each PDF(M, z = zi) by PDF(zi), where the latter is the redshift probability coming from the PDF(z) that Dahlen et al. (2013) provide for each CANDELS galaxy.”
UVUDF: ULTRAVIOLET THROUGH NEAR-INFRARED CATALOG AND PHOTOMETRIC REDSHIFTS OF GALAXIES IN THE HUBBLE ULTRA DEEP FIELD (2015, methodology): “Photometric redshifts are an accepted and robust procedure to estimate redshifts of galaxies without spectroscopic information (e.g., Koo 1985; Beńıtez 2000; Coe et al. 2006; Ilbert et al. 2006, 2009; Hildebrandt et al. 2010; Dahlen et al. 2013).”
The Star Formation Main Sequence in the Hubble Space Telescope Frontier Fields (2017, background): “This approach reduces the scatter and the fraction of outliers as well as minimizes systematics possibly associated to each individual method (Dahlen et al. 2013).”
THE RELATION BETWEEN STAR FORMATION RATE AND STELLAR MASS FOR GALAXIES AT 3.5 ⩽ z ⩽ 6.5 IN CANDELS (2014, methodology): “Our samples have been cleaned from a total of 46 objects from X-Ray (Xue et al. 2011), IR (Donley et al. 2012), and radio (Padovani et al. 2011) detected AGN, as flagged by the Dahlen et al. (2013) photo-z catalog.”
A HIGHLY CONSISTENT FRAMEWORK FOR THE EVOLUTION OF THE STAR-FORMING “MAIN SEQUENCE” FROM z ∼ 0–6 (2014, methodology): “…et al. 1999; Benítez 2000; Bolzonella et al. 2000; Collister & Lahav 2004; Ilbert et al. 2006; Feldmann et al. 2006; Brammer et al. 2008; Hildebrandt et al. 2010; Abdalla et al. 2011; Acquaviva et al. 2011; Pirzkal et al. 2012; Johnson et al. 2013; Moustakas et al. 2013; Dahlen et al. 2013).”
Science with the space-based interferometer eLISA. III: probing the expansion of the universe using gravitational wave standard sirens (2016, background): “, [81, 82]) for host galaxies with mELT,sp < mgal ≤ mELT,ph.”
The many flavours of photometric redshifts (2018, background): “The zero-point calibration was also pointed out in [70], as a way to reduce the fraction of outliers and to increase the accuracy.”