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Title: The Complete Calibration of the Color–Redshift Relation (C3R2) Survey: Survey Overview and Data Release 1

Abstract

A key goal of the Stage IV dark energy experiments Euclid , LSST, and WFIRST is to measure the growth of structure with cosmic time from weak lensing analysis over large regions of the sky. Weak lensing cosmology will be challenging: in addition to highly accurate galaxy shape measurements, statistically robust and accurate photometric redshift (photo- z ) estimates for billions of faint galaxies will be needed in order to reconstruct the three-dimensional matter distribution. Here we present an overview of and initial results from the Complete Calibration of the Color–Redshift Relation (C3R2) survey, which is designed specifically to calibrate the empirical galaxy color–redshift relation to the Euclid depth. These redshifts will also be important for the calibrations of LSST and WFIRST . The C3R2 survey is obtaining multiplexed observations with Keck (DEIMOS, LRIS, and MOSFIRE), the Gran Telescopio Canarias (GTC; OSIRIS), and the Very Large Telescope (VLT; FORS2 and KMOS) of a targeted sample of galaxies that are most important for the redshift calibration. We focus spectroscopic efforts on undersampled regions of galaxy color space identified in previous work in order to minimize the number of spectroscopic redshifts needed to map the color–redshift relation to the required accuracy. Wemore » present the C3R2 survey strategy and initial results, including the 1283 high-confidence redshifts obtained in the 2016A semester and released as Data Release 1.« less

Authors:
 [1]; ;  [2];  [3];  [4];  [5];  [6]
  1. Infrared Processing and Analysis Center, Pasadena, CA 91125 (United States)
  2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
  3. California Institute of Technology, Pasadena, CA 91125 (United States)
  4. Spitzer Science Center, Pasadena, CA 91125 (United States)
  5. Institut de Ciències de lEspai (ICE, IEEC/CSIC), E-08193 Bellaterra (Barcelona) (Spain)
  6. Department of Astronomy, University of Geneva, Ch. dEcogia 16, 1290 Versoix (Switzerland)
Publication Date:
OSTI Identifier:
22663556
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 841; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; CALIBRATION; CATALOGS; COSMOLOGY; DISTRIBUTION; GALAXIES; NONLUMINOUS MATTER; RED SHIFT; SPACE; TELESCOPES; THREE-DIMENSIONAL CALCULATIONS

Citation Formats

Masters, Daniel C., Stern, Daniel K., Rhodes, Jason D., Cohen, Judith G., Capak, Peter L., Castander, Francisco J., and Paltani, Stéphane. The Complete Calibration of the Color–Redshift Relation (C3R2) Survey: Survey Overview and Data Release 1. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA6F08.
Masters, Daniel C., Stern, Daniel K., Rhodes, Jason D., Cohen, Judith G., Capak, Peter L., Castander, Francisco J., & Paltani, Stéphane. The Complete Calibration of the Color–Redshift Relation (C3R2) Survey: Survey Overview and Data Release 1. United States. doi:10.3847/1538-4357/AA6F08.
Masters, Daniel C., Stern, Daniel K., Rhodes, Jason D., Cohen, Judith G., Capak, Peter L., Castander, Francisco J., and Paltani, Stéphane. Thu . "The Complete Calibration of the Color–Redshift Relation (C3R2) Survey: Survey Overview and Data Release 1". United States. doi:10.3847/1538-4357/AA6F08.
@article{osti_22663556,
title = {The Complete Calibration of the Color–Redshift Relation (C3R2) Survey: Survey Overview and Data Release 1},
author = {Masters, Daniel C. and Stern, Daniel K. and Rhodes, Jason D. and Cohen, Judith G. and Capak, Peter L. and Castander, Francisco J. and Paltani, Stéphane},
abstractNote = {A key goal of the Stage IV dark energy experiments Euclid , LSST, and WFIRST is to measure the growth of structure with cosmic time from weak lensing analysis over large regions of the sky. Weak lensing cosmology will be challenging: in addition to highly accurate galaxy shape measurements, statistically robust and accurate photometric redshift (photo- z ) estimates for billions of faint galaxies will be needed in order to reconstruct the three-dimensional matter distribution. Here we present an overview of and initial results from the Complete Calibration of the Color–Redshift Relation (C3R2) survey, which is designed specifically to calibrate the empirical galaxy color–redshift relation to the Euclid depth. These redshifts will also be important for the calibrations of LSST and WFIRST . The C3R2 survey is obtaining multiplexed observations with Keck (DEIMOS, LRIS, and MOSFIRE), the Gran Telescopio Canarias (GTC; OSIRIS), and the Very Large Telescope (VLT; FORS2 and KMOS) of a targeted sample of galaxies that are most important for the redshift calibration. We focus spectroscopic efforts on undersampled regions of galaxy color space identified in previous work in order to minimize the number of spectroscopic redshifts needed to map the color–redshift relation to the required accuracy. We present the C3R2 survey strategy and initial results, including the 1283 high-confidence redshifts obtained in the 2016A semester and released as Data Release 1.},
doi = {10.3847/1538-4357/AA6F08},
journal = {Astrophysical Journal},
number = 2,
volume = 841,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}
  • Calibrating the photometric redshifts of ≳10{sup 9} galaxies for upcoming weak lensing cosmology experiments is a major challenge for the astrophysics community. The path to obtaining the required spectroscopic redshifts for training and calibration is daunting, given the anticipated depths of the surveys and the difficulty in obtaining secure redshifts for some faint galaxy populations. Here we present an analysis of the problem based on the self-organizing map, a method of mapping the distribution of data in a high-dimensional space and projecting it onto a lower-dimensional representation. We apply this method to existing photometric data from the COSMOS survey selectedmore » to approximate the anticipated Euclid weak lensing sample, enabling us to robustly map the empirical distribution of galaxies in the multidimensional color space defined by the expected Euclid filters. Mapping this multicolor distribution lets us determine where—in galaxy color space—redshifts from current spectroscopic surveys exist and where they are systematically missing. Crucially, the method lets us determine whether a spectroscopic training sample is representative of the full photometric space occupied by the galaxies in a survey. We explore optimal sampling techniques and estimate the additional spectroscopy needed to map out the color–redshift relation, finding that sampling the galaxy distribution in color space in a systematic way can efficiently meet the calibration requirements. While the analysis presented here focuses on the Euclid survey, similar analysis can be applied to other surveys facing the same calibration challenge, such as DES, LSST, and WFIRST.« less
  • We present color-magnitude and morphological analysis of 54 low-redshift ultraluminous infrared galaxies (ULIRGs; 0.018 < z < 0.265 with z{sub median} = 0.151), a subset of the Infrared Astronomical Satellite 1 Jy sample, in the Sloan Digital Sky Survey (SDSS). The ULIRGs are both bright and blue: they are on average 1 mag brighter in M{sub {sup 0.1}r} than the SDSS galaxies within the same redshift range, and 0.2 mag bluer in {sup 0.1} g - {sup 0.1} r. They form a group in the color-magnitude diagram distinct from both the red sequence and the blue cloud formed by themore » SDSS galaxies: 24 out of the 52 unsaturated objects ({approx}46%) lie outside the 90% level number density contour of the SDSS galaxies. The majority (47, or {approx}87%) have the colors typical of the blue cloud, and only four ({approx}7%) sources are located in the red sequence. While ULIRGs are popularly thought to be precursors to a QSO phase, we find few (three, or {approx}6%) in the 'green valley' where the majority of the X-ray- and IR-selected active galactic nuclei (AGNs) are found. Moreover, none of the AGN-host ULIRGs are found in the green valley. For the 14 previously spectroscopic identified AGNs ({approx}28%), we perform point-spread function subtractions and find that on average the central point sources contribute less than one-third to the total luminosity, and that their high optical luminosities and overall blue colors are apparently the result of star formation activity of the host galaxies. Visual inspection of the SDSS images reveals a wide range of morphologies including many close pairs, tidal tails, and otherwise disturbed profiles, in strong support of previous studies and the general view of ULIRGs as major mergers of gas-rich disk galaxies. A detailed morphology analysis using Gini and M{sub 20} coefficients shows that slightly less than one-half ({approx}42% in g band) of the ULIRGs are located in the merger region defined by morphology studies of local galaxies, while the remaining sources are located in the region of late-type and irregular galaxies. The heterogeneous distribution of ULIRGs in the G-M{sub 20} space is qualitatively consistent with the results found by numerical simulations of disk-disk mergers, and our study also shows that the measured morphological parameters are systematically affected by the signal-to-noise ratio and thus the merging galaxies can appear in various regions of the G-M{sub 20} parameter space. We briefly discuss the origins of the uncertainties and note that the morphology measurements should be implemented with caution for low physical resolution images. In general, our results reinforce the view that ULIRGs contain young stellar populations and are mergers in progress, but we do not observe the concentration of ULIRGs/AGN in the green valley as found by other studies. Our study provides a uniform comparison sample for studying dusty starbursts at higher redshifts such as Spitzer MIPS 24 {mu}m-selected ULIRGs at z = 1-2 or submillimeter galaxies.« less
  • No abstract prepared.
  • We present the calibration of the Dark Energy Survey Year 1 (DES Y1) weak lensing source galaxy redshift distributions from clustering measurements. By cross-correlating the positions of source galaxies with luminous red galaxies selected by the redMaGiC algorithm we measure the redshift distributions of the source galaxies as placed into different tomographic bins. These measurements constrain any such shifts to an accuracy ofmore » $$\sim0.02$$ and can be computed even when the clustering measurements do not span the full redshift range. The highest-redshift source bin is not constrained by the clustering measurements because of the minimal redshift overlap with the redMaGiC galaxies. We compare our constraints with those obtained from $$\texttt{COSMOS}$$ 30-band photometry and find that our two very different methods produce consistent constraints.« less
  • We present calibrations of the redshift distributions of redMaGiC galaxies in the Dark Energy Survey Year 1 (DES Y1) and Sloan Digital Sky Survey (SDSS) DR8 data. These results determine the priors of the redshift distribution of redMaGiC galaxies, which were used for galaxy clustering measurements and as lenses for galaxy-galaxy lensing measurements in DES Y1 cosmological analyses. We empirically determine the bias in redMaGiC photometric redshift estimates using angular cross-correlations with Baryon Oscillation Spectroscopic Survey (BOSS) galaxies. For DES, we calibrate a single parameter redshift bias in three photometric redshift bins:more » $$z \in[0.15,0.3]$$, [0.3,0.45], and [0.45,0.6]. Our best fit results in each bin give photometric redshift biases of $$|\Delta z|<0.01$$. To further test the redMaGiC algorithm, we apply our calibration procedure to SDSS redMaGiC galaxies, where the statistical precision of the cross-correlation measurement is much higher due to a greater overlap with BOSS galaxies. For SDSS, we also find best fit results of $$|\Delta z|<0.01$$. We compare our results to other analyses of redMaGiC photometric redshifts.« less