Four new observational H(z) data from luminous red galaxies in the Sloan Digital Sky Survey data release seven

Tong-Jie Zhang,Han Zhang,Cong Zhang,Siqi Liu,Shuo Yuan,Yan-Chun Sun

doi:10.1088/1674-4527/14/10/002

Tong-Jie Zhang, Han Zhang + Show 4 more

Open Access

https://doi.org/10.1088/1674-4527/14/10/002

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Abstract

By adopting the differential age method, we select 17 832 luminous red galaxies from the Sloan Digital Sky Survey Data Release Seven covering redshift 0 < z < 0.4 to measure the Hubble parameter. Using the full spectrum fitting package UlySS, these spectra are reduced with single stellar population models and optimal age information from our selected sample is derived. With the decreasing age-redshift relation, four new observational H(z) data (OHD) points are obtained, which are H(z) = 69.0 ± 19.6 km s−1 Mpc−1 at z = 0.07, H(z) = 68.6 ± 26.2km s−1 Mpc−1 at z = 0.12, H(z) = 72.9 ± 29.6 km s−1 Mpc−1 at z = 0.2 and H(z)=88.8 ± 36.6 km s−1 Mpc−1 at z = 0.28, respectively. Combined with 21 other available OHD data points, the performance of the constraint on both flat and non-flat ΛCDM models is presented.

Highlights

A variety of cosmological observations are used for a better understanding of the expansion of the Universe quantitatively, for example the mapping of the cosmic microwave background (CMB) anisotropies (Spergel et al, 2007; Komatsu et al, 2011), the measurement of baryon acoustic oscillation (BAO) peaks (Eisenstein et al, 2005; Percival et al, 2010), measurements of ‘standard candles’ such as the redshift-distance relationship of type Ia supernovae (SNIa) (SNIa; Riess et al, 1998; Hicken et al, 2009) and gamma-ray bursts (GRBs) (GRBs; Ghirlanda et al, 2004; Li et al, 2008)
Take the first subsample for example. We divide it into several bins from 3 to 20, select the oldest galaxy of each bin as a set of t(zi) and fit the corresponding points of t(zi) with a straight line to get a candidate of observational H(z) data (OHD) of this subsample
We present our measurements of four new OHD data points from the ages of passivelyevolving galaxies at redshift 0

Summary

INTRODUCTION

A variety of cosmological observations are used for a better understanding of the expansion of the Universe quantitatively, for example the mapping of the cosmic microwave background (CMB) anisotropies (Spergel et al, 2007; Komatsu et al, 2011), the measurement of baryon acoustic oscillation (BAO) peaks (Eisenstein et al, 2005; Percival et al, 2010), measurements of ‘standard candles’ such as the redshift-distance relationship of type Ia supernovae (SNIa) (SNIa; Riess et al, 1998; Hicken et al, 2009) and gamma-ray bursts (GRBs) (GRBs; Ghirlanda et al, 2004; Li et al, 2008). Compared with other spectra selection work, ‘Carson & Nichol sample’ calibrates, for the first time, the SDSS spectra on Lick/Image Dissector Scanner (IDS) system Their general selected criterion steps are as follows. When fitting the observed spectrum (Fobs(λ)), the package uses a linear combination of k non-linear components (CMPi) with weight Wi respectively to approximate it. In this process, the composite model is possibly convolved with a line-of-sight velocity distribution (LOSVD), multiplied by an nth order polynomial of Pn(λ) and summed to another polynomial of Qm(λ) (for more details please refer to Koleva et al, 2009b): i=k. The reliability and robustness of using ULySS to the study of the history of stellar population has been verified (e.g., Koleva et al, 2009c,a)

Model Selection and Matching resolution

Single Stellar Population Fit

Findings

CONCLUSION AND DISCUSSION