Prospects for indirect MeV Dark Matter detection with Gamma Rays in light of Cosmic Microwave Background Constraints

The self-annihilation of dark matter particles with mass in the MeV range can produce gamma rays via prompt or secondary radiation. The annihilation rate for such light dark matter particles is however tightly constrained by cosmic microwave background (CMB) data. Here we explore the possibility of discovering MeV dark matter annihilation with future MeV gamma-ray telescopes taking into account the latest and future CMB constraints. We study the optimal energy window as a function of the dominant annihilation final state. We consider both the (conservative) case of the dwarf spheroidal galaxy Draco and the (more optimistic) case of the Galactic center. We find that for certain channels, including those with one or two monochromatic photon(s) and one or two neutral pion(s), a detectable gamma-ray signal is possible for both targets under consideration, and compatible with CMB constraints. For other annihilation channels, however, including all leptonic annihilation channels and two charged pions, CMB data rule out any significant signal of dark matter annihilation at future MeV gamma-ray telescopes from dwarf galaxies, but possibly not for the Galactic center.Comment: 10 pages, 6 figures, version to appear on PR

Analysis of the Very Inner Milky Way Dark Matter Distribution and Gamma-Ray Signals

We analyze the possibility that the HESS gamma-ray source at the Galactic Center could be explained as the secondary flux produced by annihilation of TeV Dark Matter (TeVDM) particles with locally enhanced density, in a region spatially compatible with the HESS observations themselves. We study the inner 100 pc considering (i) the extrapolation of several density profiles from state-of-the-art N-body + Hydrodynamics simulations of Milky Way-like galaxies, (ii) the DM spike induced by the black hole, and (iii) the DM particles scattering off by bulge stars. We show that in some cases the DM spike may provide the enhancement in the flux required to explain the cut-off in the HESS J1745-290 gamma-ray spectra as TeVDM. In other cases, it may helps to describe the spatial tail reported by HESS II at angular scales < 0.54 degrees towards Sgr A.Comment: 6 pages, 3 figures, 1 table. Accepted for publication in Physical Review D - Rapid Communication

What did Constantine learn in 325? Constantine’s theological declarations before, at and after Nicaea

The analysis of the corpus of letters of the emperor Constantine, in particular, the one he addressed to the synod of Arles in 314, the one he addressed to the Church of Nicomedia in 325 and the one he addressed to Arius in 333, and of Eusebius of Caesarea’s account of the Synod of Nicaea in 325, allows to evaluate the evolution of the theological representations of the first Christian emperor. Constantine’s interest was not only political, but he also was able to listen to and understand the theological milestones of the controversy.El análisis del corpus de las cartas del emperador Constantino, en particular la que dirigió al sínodo de Arles en 314, la que dirigió a la Iglesia de Nicomedia en 325, y la que dirigió a Arrio en 333, y del relato de Eusebio de Cesarea acerca del concilio de Nicea de 325, permiten evaluar la evolución de las representaciones teológicas del primer emperador cristiano. El interés de Constantino no fue sólo político sino que él supo también escuchar y entender cuáles eran los hitos teológicos de la controversia