1705.10031
An evaluation of cosmological models from expansion and growth of structure measurements
Zhai, Blanton, Slosar, Tinker
Compare a large suite of theoretical cosmological models to observational data from the CMB, BAO measurements of expansion, Type Ia SNe measurements of expansion, z-space distortion measurements of the growth of structure, and the local Hubble constant. The theoretical models include parameterizations of DE as well as physical models of DE and modified gravity. Determine the constraints on the model parameters, incorporating the z space distortion data directly in the analysis. To determine whether models can be ruled out, evaluate the p value (the probability under the model of obtaining data as bad or worse than the observed data). In the comparison, find the well known tension of H0 with the other data; no model resolves this tension successfully. Among the models considered, the LS growth of structure data does not affect the modified gravity models as a category particularly differently than DE models; it matters for some modified gravity models but not others, and the same is true for DE models. Compute predicted observables for each model under current observational constraints, and identify models for which future observational constraints will be particularly informative.
1705.10256
The extragalactic background might revisited and the cosmic photon-photon opacity
Franceschini, Rodighiero
In addition to its relevant astrophysical and cosmological significance, the Extragalactic Background Light (EBL) is a fundamental source of opacity for cosmic high energy photons, as well as a limitation for the propagation of high-energy particles in the Universe. Review the previously published determinations of the EBL photon density in the Universe and its evolution with cosmic time, in the light of recent surveys of IR sources at long wavelengths. Exploit deep survey observations by Herschel and Spitzer, matched to optical and NIR photometric and spectroscopic data, to re-estimate number counts and luminosity functions longwords of a few microns, and the contribution of resolved sources to the EBL. These new data indicate slightly lower photon densities in the mid- and far-infrared and sub-millimeter compared to previous determinations. This implies slightly lower cosmic opacity for photon-photon interactions. The new data do not modify previously published EBL modeling in the UV-optical and near-IR up to several microns, while reducing the photon density at longer wavelengths. This improved model of the EBL alleviates some tension that had emerged in the interpretation of the highest-energy TeV observations of local blazers, reducing the case for new physics beyond the standard model (e.g. violations of the Lorenz Invariance, LIV, at the highest particles energies), or for exotic astrophysics, that had sometimes been called for to explain it. Applications of this improved EBL model on current data are considered, as well as perspectives for future instrumentation, the Cherenkov Telescope Array (CTA) in particular.
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