Angular correlation function of 1.5 million LRGs: clustering evolution and a search for BAO

TL;DR

This study measures the angular correlation function of over 1.5 million luminous red galaxies from SDSS data across different redshifts, analyzing clustering evolution and searching for baryon acoustic oscillations, providing insights into galaxy clustering and halo models.

Contribution

It presents the largest photometric LRG sample analysis, revealing clustering behavior and evolution consistent with halo occupation and LCDM models, and searches for BAO features.

Findings

Clustering shows a break at ~1 h^-1 Mpc, indicating transition between 1- and 2-halo terms.

No significant clustering evolution observed from z ~ 0.35 to 0.7 at 1-20 h^-1 Mpc.

Small-scale clustering evolution suggests 2-3% per Gyr LRG merging rate.

Abstract

We present the angular correlation function measured from photometric samples comprising 1,562,800 luminous red galaxies (LRGs). Three LRG samples were extracted from the Sloan Digital Sky Survey (SDSS) imaging data, based on colour-cut selections at redshifts, z ~ 0.35, 0.55 and 0.7 as calibrated by the spectroscopic surveys, SDSS-LRG, 2dF-SDSS LRG and QSO (2SLAQ), and the AAOmega LRG survey. The galaxy samples cover ~7600 s.q.deg of the sky, probing a total cosmic volume of ~5.5 h^-3} Gpc^3. The small and intermediate scale correlation functions generally show significant deviations from a single power-law fit with a well-detected break at ~1 h^-1 Mpc, consistent with the transition scale between the 1- and 2-halo terms in halo occupation models. For galaxy separations 1-20 h^-1 Mpc and at fixed luminosity, we see virtually no evolution of the clustering with redshift and the data is consistent with a simple high peaks biasing model where the comoving LRG space density is constant with z. At fixed z, the LRG clustering amplitude increases with luminosity in accordance with the simple high peaks model, with a typical LRG dark matter halo mass 10^13-10^14 h^-1 M_sol. For r < 1 h^-1 Mpc, the evolution is slightly faster and the clustering decreases towards high redshift consistent with a virialised clustering model. However, assuming the HOD and LCDM halo merger frameworks, ~2-3 per cent per Gyr of the LRGs is required to merge in order to explain the small scales clustering evolution, consistent with previous results [abridge].