The clustering of LRGs in the DECaLS DR8 footprint: distance constraints from baryon acoustic oscillations using photometric redshifts

TL;DR

This paper uses photometric redshift data from the DECaLS survey to measure cosmic distances via baryon acoustic oscillations, providing constraints on the angular diameter distance and Hubble constant consistent with the standard cosmological model.

Contribution

It applies a wedge correlation function approach to photometric redshift data from DECaLS to measure cosmic distances, extending previous simulation-based methods to real observational data.

Findings

Measured angular diameter distances at z=0.69 and z=0.87 with ~5-6% errors.

Derived H0 value of 67.59 km/s/Mpc consistent with other BAO results.

Confirmed the viability of using photometric redshifts for cosmological distance measurements.

Abstract

A photometric redshift sample of Luminous Red Galaxies (hereafter LRGs) obtained from The DECam Legacy Survey (DECaLS) is analysed to probe cosmic distances by exploiting the wedge approach of the two-point correlation function. Although the cosmological information is highly contaminated by the uncertainties existing in the photometric redshifts from the galaxy map, an angular diameter distance can be probed at the perpendicular configuration in which the measured correlation function is minimally contaminated. An ensemble of wedged correlation functions selected up to a given threshold based on having the least contamination was studied in the previous work (arXiv:1903.09651v2 [astro-ph.CO]) using simulations, and the extracted cosmological information was unbiased within this threshold. We apply the same methodology for analysing the LRG sample from DECaLS which will provide the optical imaging for targeting two-thirds of the DESI footprint and measure the angular diameter distances at $z=0.69$ and $z=0.87$ to be $D_{A}(0.697)=(1499 \pm 77\,\mathrm{Mpc})(r_{d}/r_{d,fid})$ and $D_{A}(0.874)=(1680 \pm 109\,\mathrm{Mpc})(r_{d}/r_{d,fid})$ with a fractional error of 5.14% and 6.48% respectively. We obtain a value of $H_{0}=67.59\pm5.52$ km/s/Mpc which supports the $H_0$ measured by all other BAO results and is consistent with $\Lambda$CDM model.