Search Publications
Cosmological constraints on galaxy cluster structure
Alcaniz, J. S.; Holanda, R. F. L.
Observations of galaxy clusters (GC's) are a powerful tool to probe the evolution of the Universe at z < 2 . However, the real shape and structure of these objects are not completely understood and the assumption of asphericity is often used in several cosmological tests. In this work, we propose methods to infer the elongation of the gas distr…
Exploiting cross correlations and joint analyses
Doré, O.; Honscheid, K.; Linder, E. +13 more
The nature of the dark energy thought to be causing the accelerating expansion of the Universe is one of the most compelling questions in all of science. Any of the explanations for the accelerated expansion, whether a new field, a negative pressure fluid, or a modification to General Relativity will signal new physics and have a profound effect o…
Cosmic rays in the heliosphere: Observations
Moraal, Harm
This contribution to the 100th commemoration of the discovery of cosmic rays (6-8 August, 2012 in Bad Saarow, Germany) is about observations of those cosmic rays that are sensitive to the structure and the dynamics of the heliosphere. This places them in the energy range of 107-1010 eV. For higher energies the heliosphere bec…
The extragalactic background light and the gamma-ray opacity of the universe
Dwek, Eli; Krennrich, Frank
The extragalactic background light (EBL) is one of the fundamental observational quantities in cosmology. All energy releases from resolved and unresolved extragalactic sources, and the light from any truly diffuse background, excluding the cosmic microwave background (CMB), contribute to its intensity and spectral energy distribution. It therefor…
Multiwavelength Astronomy and CTA: X-rays
Takahashi, Tadayuki; Uchiyama, Yasunobu; Stawarz, Łukasz
We discuss how future X-ray instruments which are under development can contribute to our understanding of the non-thermal Universe. Much progress has been made in the field of X-ray Astronomy recently, thanks to the operation of modern X-ray telescopes such as Chandra, XMM-Newton, Suzaku, and SWIFT, but more in-depth investigation awaits future m…
A new limit on Planck scale Lorentz violation from γ-ray burst polarization
Stecker, Floyd W.
Constraints on possible Lorentz invariance violation (LIV) to first order in E/ MPlanck for photons in the framework of effective field theory (EFT) are discussed, taking cosmological factors into account. Then, using the reported detection of polarized soft γ-ray emission from the γ-ray burst GRB041219a that is indicative of an absence…
Searching for modifications to the exponential radioactive decay law with the Cassini spacecraft
Cooper, Peter S.
Data from the power output of the radioisotope thermoelectric generators aboard the Cassini spacecraft are used to test the conjecture that small deviations observed in terrestrial measurements of the exponential radioactive decay law are correlated with the Earth-Sun distance. No significant deviations from exponential decay are observed over a r…
Color, 3D simulated images with shapelets
Mobasher, Bahram; Massey, Richard; Rhodes, Jason +3 more
We present a method to simulate color, 3-dimensional images taken with a space-based observatory by building off of the established shapelets pipeline. The simulated galaxies exhibit complex morphologies, which are realistically correlated between, and include, known redshifts. The simulations are created using galaxies from the 4 optical and near…
Search for the light dark matter with an X-ray spectrometer
Neronov, A.; Boyarsky, A.; Ruchayskiy, O. +1 more
Sterile neutrinos with the mass in the keV range are interesting warm dark matter (WDM) candidates. The restrictions on their parameters (mass and mixing angle) obtained by current X-ray missions ( XMM-Newton or Chandra) can only be improved by less than an order of magnitude in the near future. Therefore the new strategy of search is needed. We c…
Towards a fluid description of directional particle flux observations
Moussas, X.; Polygiannakis, J. M.; Alevizos, A.
We propose that, whenever directional flux measurements of a population of particles (e.g. solar energetic particles, cosmic rays, solar wind plasma) of well-defined energy resolution are available, new macroscopic fluid-like quantities (namely the energy dependent analog of density, mean velocity, anisotropic pressure, temperature and heat flux) …