Four New Observational $H(z)$ Data From Luminous Red Galaxies of Sloan Digital Sky Survey Data Release Seven

TL;DR

This paper presents four new observational measurements of the Hubble parameter $H(z)$ using luminous red galaxies from SDSS DR7, employing the differential age method and spectral fitting, and combines these with existing data to constrain cosmological models.

Contribution

The study introduces four new $H(z)$ data points derived from SDSS DR7 LRGs using spectral fitting and the differential age method, enhancing the dataset for cosmological parameter estimation.

Findings

Four new $H(z)$ measurements at $z=0.07, 0.12, 0.2, 0.28$ with uncertainties.

Combined data improves constraints on flat and non-flat $\\Lambda$CDM models.

Demonstrates the effectiveness of LRGs and spectral fitting in cosmological measurements.

Abstract

By adopting the differential age method, we utilize selected 17832 luminous red galaxies (LRGs) from Sloan Digital Sky Survey Data Release Seven (SDSS DR7) covering redshift $0<z<0.4$ to measure Hubble parameters. Using a full spectrum fitting package UlySS, these spectra are reduced with single stellar population (SSP) models and optimal age information of our selected sample are derived. With the decreasing age-redshift relation, four new observational $H(z)$ data (OHD) points are obtained, which are $H(z)=69.0\pm19.6$ km s$^{-1}$ Mpc$^{-1}$ at $z=0.07$, $H(z)=68.6\pm26.2$ km s$^{-1}$ Mpc$^{-1}$ at $z=0.12$, $H(z)$=$72.9\pm29.6$ km s$^{-1}$ Mpc$^{-1}$ at $z=0.2$ and $H(z)$=$88.8\pm36.6$ km s$^{-1}$ Mpc$^{-1}$ at $z=0.28$, respectively. Combined with other 21 available OHD data points, a performance of constraint on both flat and non-flat $\Lambda$CDM model is presented.