Higher order angular galaxy correlations in the SDSS: Redshift and color dependence of nonlinear bias

Ashley J. Ross, Robert J. Brunner, Adam D. Myers

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We present estimates of the N-point galaxy, area-averaged, angular correlation functions ω̄N(θ) for N = 2, . . . , 7 for galaxies from the fifth data release of the Sloan Digital Sky Survey. Our parent sample is selected from galaxies with 18 ≤ r ≤ 21 and is the largest ever used to study higher order correlations. We subdivide this parent sample into two volume-limited samples using photometric redshifts, and these two samples are further subdivided by magnitude, redshift, and color (producing early- and late-type galaxy samples) to determine the dependence of ω̄N(θ) on luminosity, redshift, and galaxy type. We measure ω̄N(θ) using oversampling techniques and use them to calculate the projected sN. Using models derived from theoretical power spectra and perturbation theory, we measure the bias parameters b1 and c2, finding that the large differences in both bias parameters (b1 and c2) between early- and late-type galaxies are robust against changes in redshift, luminosity, and σ8, and that both terms are consistently smaller for late-type galaxies. By directly comparing their higher order correlation measurements, we find large differences in the clustering of late-type galaxies at redshifts lower than 0.3 and those at redshifts higher than 0.3, both at large scales (c2 is larger by ∼0.5 at z > 0.3) and small scales (large amplitudes are measured at small scales only for z > 0.3, suggesting much more merger-driven star formation at z > 0.3). Finally, our measurements of c2 suggest both that σ8 < 0.8 and that c 2 is negative.

Original languageEnglish (US)
Pages (from-to)67-84
Number of pages18
JournalAstrophysical Journal
Issue number1 PART 1
StatePublished - Aug 10 2007


  • Cosmology: observations
  • Stars: formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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