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redMaGiC: Selecting Luminous Red Galaxies from the DES Science Verification Data

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arxiv 1507.05460 v1 pith:2HHBPUOI submitted 2015-07-20 astro-ph.IM astro-ph.COastro-ph.GA

classification astro-ph.IMastro-ph.COastro-ph.GA
keywords redmagicalgorithmdatabiasescomovingdensitygalaxiesluminous
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

We introduce redMaGiC, an automated algorithm for selecting Luminous Red Galaxies (LRGs). The algorithm was specifically developed to minimize photometric redshift uncertainties in photometric large-scale structure studies. redMaGiC achieves this by self-training the color-cuts necessary to produce a luminosity-thresholded LRG sample of constant comoving density. We demonstrate that redMaGiC photozs are very nearly as accurate as the best machine-learning based methods, yet they require minimal spectroscopic training, do not suffer from extrapolation biases, and are very nearly Gaussian. We apply our algorithm to Dark Energy Survey (DES) Science Verification (SV) data to produce a redMaGiC catalog sampling the redshift range $z\in[0.2,0.8]$. Our fiducial sample has a comoving space density of $10^{-3}\ (h^{-1} Mpc)^{-3}$, and a median photoz bias ($z_{spec}-z_{photo}$) and scatter $(\sigma_z/(1+z))$ of 0.005 and 0.017 respectively. The corresponding $5\sigma$ outlier fraction is 1.4%. We also test our algorithm with Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) and Stripe 82 data, and discuss how spectroscopic training can be used to control photoz biases at the 0.1% level.

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Forward citations

Cited by 3 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Dark Energy Survey Year 6 Results: Redshift Calibration of the MagLim++ Lens Sample

    astro-ph.CO 2025-09 conditional novelty 6.0 of 10

    DES Y6 calibrates MagLim++ lens galaxy redshift distributions to 1-2% mean accuracy using SOM-based photometric redshifts plus clustering redshifts, with uncertainties compressed into a few modes.

  2. Dark Energy Survey Year 3 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing

    astro-ph.CO 2021-05 accept novelty 6.0 of 10

    DES Y3 3x2pt analysis constrains S8=0.776±0.017 and Ωm=0.339±0.032 in flat ΛCDM, consistent with Planck CMB results at p=0.13-0.48.

  3. Modeling Redshift Uncertainties in Roman Weak Lensing Cosmology

    astro-ph.CO 2026-02 conditional novelty 4.0 of 10

    A PCA-based redshift uncertainty model, implemented for Roman in CoCoA, matches or outperforms the nine-bin mean-shift model at mitigating S8 and Omega_m biases in simulated cosmic shear analyses.

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