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Clustering analysis of high-redshift luminous red galaxies in Stripe 82

Nikoloudakis, N.; Shanks, T.; Sawangwit, U.

Clustering analysis of high-redshift luminous red galaxies in Stripe 82 Thumbnail


N. Nikoloudakis

T. Shanks

U. Sawangwit


We present a clustering analysis of luminous red galaxies (LRGs) in Stripe 82 from the Sloan Digital Sky Survey (SDSS). We study the angular two-point autocorrelation function, w(θ), of a selected sample of over 130 000 LRG candidates via colour-cut selections in izK with the K-band coverage coming from UKIRT (United Kingdom Infrared Telescope) Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). We have used the cross-correlation technique of Newman to establish the redshift distribution of the LRGs. Cross-correlating them with SDSS quasi-stellar objects (QSOs), MegaZ-LRGs and DEEP Extragalactic Evolutionary Probe 2 (DEEP2) galaxies, implies an average redshift of the LRGs to be z ≈ 1 with space density, ng ≈ 3.20 ± 0.16 × 10−4 h3 Mpc−3. For θ ≤ 10 arcmin (corresponding to ≈10 h−1 Mpc), the LRG w(θ) significantly deviates from a conventional single power law as noted by previous clustering studies of highly biased and luminous galaxies. A double power law with a break at rb ≈ 2.4 h−1 Mpc fits the data better, with best-fitting scale length, r0, 1 = 7.63 ± 0.27 h−1 Mpc and slope γ1 = 2.01 ± 0.02 at small scales and r0, 2 = 9.92 ± 0.40 h−1 Mpc and γ2 = 1.64 ± 0.04 at large scales. Due to the flat slope at large scales, we find that a standard Λ cold dark matter (Λ CDM) linear model is accepted only at 2–3σ, with the best-fitting bias factor, b = 2.74 ± 0.07. We also fitted the halo occupation distribution (HOD) models to compare our measurements with the predictions of the dark matter clustering. The effective halo mass of Stripe 82 LRGs is estimated as Meff = 3.3 ± 0.6 × 1013 h−1 M⊙. But at large scales, the current HOD models did not help explain the power excess in the clustering signal. We then compare the w(θ) results to the results of Sawangwit et al. from three samples of photometrically selected LRGs at lower redshifts to measure clustering evolution. We find that a long-lived model may be a poorer fit than at lower redshifts, although this assumes that the Stripe 82 LRGs are luminosity-matched to the AAΩ LRGs. We find stronger evidence for evolution in the form of the z ≈ 1 LRG correlation function with the above flat two-halo slope maintaining to s ≳ 50 h− 1 Mpc. Applying the cross-correlation test of Ross et al., we find little evidence that the result is due to systematics. Otherwise, it may represent evidence for primordial non-Gaussianity in the density perturbations at early times, with flocalNL = 90 ± 30.


Nikoloudakis, N., Shanks, T., & Sawangwit, U. (2013). Clustering analysis of high-redshift luminous red galaxies in Stripe 82. Monthly Notices of the Royal Astronomical Society, 429(3), 2032-2051.

Journal Article Type Article
Publication Date Mar 1, 2013
Deposit Date Mar 18, 2013
Publicly Available Date Jun 10, 2014
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 429
Issue 3
Pages 2032-2051
Keywords Cosmology: observations, Galaxies: evolution-high-redshift, Large-scale structure of Universe.


Published Journal Article (3 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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