1201.6658 (Michele Moresco et al.)

New constraints on cosmological parameters and neutrino properties using
the expansion rate of the Universe to z~1.75    [PDF]

Michele Moresco, Licia Verde, Lucia Pozzetti, Raul Jimenez, Andrea Cimatti

We have assembled a compilation of observational Hubble parameter
measurements estimated with the differential evolution of cosmic chronometers,
in the redshift range 0CMB data, to derive new constraints on several cosmological parameters. The new
Hubble parameter data are very useful at breaking some of the parameter
degeneracies present in CMB-only analysis and in constraining possible
deviations from the standard (minimal) flat \Lambda CDM model. The H(z) data
are especially useful in constraining \Omega_k and \Omega_DE in models that
allow a variation of those parameters, yielding constraints that are
competitive with those obtained using Supernovae and/or baryon acoustic
oscillations. We also find that our H(z) data are useful to constrain
parameters that do no affect directly the expansion history, by breaking or
reducing degeneracies with other parameters. We find that N_rel=3.5\pm0.3 using
WMAP 7-years data in combination with South Pole Telescope data and our H(z)
determinations N_rel=3.7\pm0.4 using Atacama cosmology telescope data instead
of South pole telescope). We exclude N_rel>4 at 95% confidence level (at 74%
confidence level using the Atacama Cosmology Telescope instead). We also put
competitive limits on the sum of neutrino masses, m_\nu<0.24 eV at 68%
confidence level. These results have been proven to be extremely robust to the
initial choice of stellar population synthesis model adopted to estimate H(z).

View original: http://arxiv.org/abs/1201.6658