Constraining the expansion rate of the Universe using low-redshift ellipticals as cosmic chronometers

Michele Moresco; Raul Jimenez; Andrea Cimatti; Lucia Pozzetti

doi:10.1088/1475-7516/2011/03/045

paper

Constraining the expansion rate of the Universe using low-redshift ellipticals as cosmic chronometers

arXiv:1010.0831 · doi:10.1088/1475-7516/2011/03/045

Abstract

We present a new methodology to determine the expansion history of the Universe analyzing the spectral properties of early type galaxies (ETG). We found that for these galaxies the 4000Åbreak is a spectral feature that correlates with the relative ages of ETGs. In this paper we describe the method, explore its robustness using theoretical synthetic stellar population models, and apply it using a SDSS sample of $\sim$ 14 000 ETGs. Our motivation to look for a new technique has been to minimise the dependence of the cosmic chronometer method on systematic errors. In particular, as a test of our method, we derive the value of the Hubble constant $H_{0} = 72.6 \pm 2.8$ (stat) $\pm 2.3$ (syst) (68% confidence), which is not only fully compatible with the value derived from the Hubble key project, but also with a comparable error budget. Using the SDSS, we also derive, assuming w=constant, a value for the dark energy equation of state parameter $w = - 1 \pm 0.2$ (stat) $\pm 0.3$ (syst). Given the fact that the SDSS ETG sample only reaches $z \sim 0.3$ , this result shows the potential of the method. In future papers we will present results using the high-redshift universe, to yield a determination of H(z) up to $z \sim 1$ .

25 pages, 17 figures, JCAP accepted

Constraining the expansion rate of the Universe using low-redshift ellipticals as cosmic chronometers

Abstract

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