The SDSS DR7 Galaxy Angular Power Spectrum

TL;DR

This paper measures the galaxy angular power spectrum from SDSS DR7 data, analyzing systematic effects, and compares it with theoretical models to estimate cosmological parameters like matter density and galaxy bias.

Contribution

It presents a detailed measurement of the galaxy angular power spectrum from SDSS DR7 using quadratic estimation and KL-compression, including systematic tests and redshift evolution analysis.

Findings

Measured angular power spectrum up to l=200 and l=1000 for different samples.

Found minimal impact of seeing and reddening on measurements.

Estimated cosmological parameters: Ω_m ≈ 0.31, bias ≈ 0.94.

Abstract

We calculate the angular power spectrum of galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) by using a quadratic estimation method with KL-compression. The primary data sample includes over 18 million galaxies covering more than 5,700 square degrees after masking areas with bright objects, reddening greater than 0.2 magnitudes, and seeing of more than 1.5 arcseconds. We test for systematic effects by calculating the angular power spectrum by SDSS stripe and find that these measurements are minimally affected by seeing and reddening. We calculate the angular power spectrum for l \leq 200 multipoles by using 40 bandpowers for the full sample, and l \leq 1000 multipoles using 50 bandpowers for individual stripes. We also calculate the angular power spectrum for this sample separated into 3 magnitude bins with mean redshifts of z = 0.171, z = 0.217, and z = 0.261 to examine the evolution of the angular power spectrum. We determine the theoretical linear angular power spectrum by projecting the 3D power spectrum to two dimensions for a basic comparison to our observational results. By minimizing the {\chi}^2 fit between these data and the theoretical linear angular power spectrum we measure a loosely-constrained fit of {\Omega}_m = 0.31^{+0.18}_{-0.11} with a linear bias of b = 0.94 \pm 0.04.