The Power Spectrum of Galaxy Clustering in the Las Campanas Redshift Survey

Abstract

The Las Campanas Redshift Survey (LCRS) contains 23, 697 galaxies, with an average redshift z = 0.1, distributed over six 15 × 80° slices in the north and south galactic caps. We have computed the power spectrum P(k) for magnitude-limited samples of LCRS galaxies over wavelengths λ = 2π/k = 5–400 h−1 Mpc. The LCRS P(k) may be approximated as ∝ k−1.8±0.1 for small scales λ = 5–30 h−1 Mpc, changing to ∝k1 ± 1 for large scales λ ≈ 200-400 h−1 Mpc. The overall amplitude corresponds to σ8 = 1.0 ± 0.1 in redshift space. Comparisons to the power spectra of other redshift surveys will be presented; the LCRS results agree best with those from the combined Center for Astrophysics (CfA2) and Southern Sky redshift surveys (SSRS2). For λ 100 h−1 Mpc, the LCRS results are consistent with those of other surveys, given the large errors among all the surveys on these scales. For λ 100 h−1 Mpc, the LCRS P(k) is well determined and similar in shape to the P(k) of other surveys, but with an amplitude differing from some of the other samples, possibly because of inherent clustering differences among different types of galaxies. In particular, power spectrum measurements for volume-limited LCRS samples show that galaxies brighter than about M* − 1 appear about 50% more strongly clustered than those fainter. Also, a sample of LCRS emission galaxies shows 30% weaker clustering than the full LCRS sample. Comparisons to N-body models show that the LCRS power spectrum lies intermediate between that of a standard flat Ω0h = 0.5 cold dark matter (CDM) model and an open Ω0h = 0.2 model, both normalized to σ8 = 1 for galaxies. On large scales λ 40 h−1 Mpc, we have fit the LCRS results to various linear CDM models, and find that a number of them could meet the constraints set by the LCRS power spectrum, the Hubble constant range 0.5 h 0.8, the abundance of galaxy clusters, and the reasonable assumption that LCRS galaxies are roughly unbiased tracers of the mass, relative to the normalization provided by the 4 year COBE DMR data. The possibilities include open CDM or flat nonzero cosmological-constant CDM models with Ω0 ≈ 0.4–0.6 and shape parameter Γ ≈ Ω0h ≈ 0.2–0.3, as well as flat Ω0 = 1 models with massive neutrino density Ωv ≈ 0.2–0.3 or a spectral tilt n ≈ 0.7–0.8.