Data di Pubblicazione:
2012
Citazione:
Impact of H-0 prior on the evidence for dark radiation / E. Calabrese, M. Archidiacono, A. Melchiorri, B. Ratra. - In: PHYSICAL REVIEW. D. PARTICLES, FIELDS, GRAVITATION, AND COSMOLOGY. - ISSN 1550-2368. - 86:4(2012), pp. 043520.1-043520.8.
Abstract:
Recent analyses that include cosmic microwave background (CMB) anisotropy measurements from the Atacama Cosmology Telescope and the South Pole Telescope have hinted at the presence of a dark radiation component at more than two standard deviations. However, this result depends sensitively on the assumption of an Hubble Space Telescope prior on the Hubble constant, where H-0 = 73.8 +/- 2.4 km/s/Mpc at 68% c.l.. Here we repeat this kind of analysis assuming a prior of H-0 = 68 +/- 2.8 km/s/Mpc at 68% c.l., derived from a median statistics (MS) analysis of 537 non-CMB H-0 measurements from Huchra's compilation. This prior is fully consistent with the value of H-0 = 69.7 +/- 2.5 km/s/Mpc at 68% c.l. obtained from CMB measurements under assumption of the standard ACDM model. We show that with the MS H-0 prior the evidence for dark radiation is weakened to similar to 1.2 standard deviations. Parametrizing the dark radiation component through the effective number of relativistic degrees of freedom N-eff, we find N-eff 3.98 +/- 0.37 at 68% c.l. with the Hubble Space Telescope prior and N-eff 3.52 +/- 0.39 at 68% c.l. with the MS prior. We also discuss the implications for current limits on neutrino masses and on primordial Helium abundances.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
variable cosmological constant; gas mass fraction; hubble constant; power spectrum; median statistics; redshift data; scalar-field; constraints; telescope; parameters
Elenco autori:
E. Calabrese, M. Archidiacono, A. Melchiorri, B. Ratra
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