We present a new methodology to determine the expansion history of the Universe analyzing the spectral properties of early-type galaxies (ETG), based on the study of the redshift dependence of the 4000 Å break. In this paper we describe the method, explore its robustness using theoretical synthetic stellar population models, and apply it using a SDSS sample of ~ 14 000 ETGs. Our motivation to look for a new technique has been to minimize 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 H0 = 72.6 +/-2.9(stat)+/-2.3(syst) km Mpc-1s-1 (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 +/-0.2(stat)+/-0.3(syst). Given the fact that the SDSS ETG sample only reaches z ~ 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 ~ 1.
Constraining the expansion rate of the Universe using low-redshift ellipticals as cosmic chronometers
MORESCO, MICHELE ENNIO MARIA;CIMATTI, ANDREA;
2011
Abstract
We present a new methodology to determine the expansion history of the Universe analyzing the spectral properties of early-type galaxies (ETG), based on the study of the redshift dependence of the 4000 Å break. In this paper we describe the method, explore its robustness using theoretical synthetic stellar population models, and apply it using a SDSS sample of ~ 14 000 ETGs. Our motivation to look for a new technique has been to minimize 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 H0 = 72.6 +/-2.9(stat)+/-2.3(syst) km Mpc-1s-1 (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 +/-0.2(stat)+/-0.3(syst). Given the fact that the SDSS ETG sample only reaches z ~ 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 ~ 1.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
