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Impact of H0 prior on the evidence for dark radiation

Calabrese, Erminia ORCID:, Archidiacono, Maria, Melchiorri, Alessandro and Ratra, Bharat 2012. Impact of H0 prior on the evidence for dark radiation. Physical Review D 86 (4) , 043520. 10.1103/PhysRevD.86.043520

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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 H0 ¼ 73:8 � 2:4 km=s=Mpc at 68% c.l.. Here we repeat this kind of analysis assuming a prior of H0 ¼ 68 � 2:8 km=s=Mpc at 68% c.l., derived from a median statistics (MS) analysis of 537 non-CMB H0 measurements from Huchra’s compilation. This prior is fully consistent with the value of H0 ¼ 69:7 � 2:5 km=s=Mpc at 68% c.l. obtained from CMB measurements under assumption of the standard �CDM model. We show that with the MS H0 prior the evidence for dark radiation is weakened to 1:2 standard deviations. Parametrizing the dark radiation component through the effective number of relativistic degrees of freedom Neff, we find Neff ¼ 3:98 � 0:37 at 68% c.l. with the Hubble Space Telescope prior and Neff ¼ 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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Publisher: American Physical Society
ISSN: 2470-0010
Date of First Compliant Deposit: 9 October 2017
Date of Acceptance: 7 June 2012
Last Modified: 22 May 2023 16:28

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