The possible gamma-ray excess in the inner Galaxy and the Galactic center (GC) suggested by Fermi -LAT observations has triggered a large number of studies. It has been interpreted as a variety of different phenomena such as a signal from WIMP dark matter annihilation, gamma-ray emission from a population of millisecond pulsars, or emission from cosmic rays injected in a sequence of burst-like events or continuously at the GC. We present the first comprehensive study of model systematics coming from the Galactic diffuse emission in the inner part of our Galaxy and their impact on the inferred properties of the excess emission at Galactic latitudes 2 • < |b| < 20 • and 300 MeV to 500 GeV. We study both theoretical and empirical model systematics, which we deduce from a large range of Galactic diffuse emission models and a principal component analysis of residuals in numerous test regions along the Galactic plane. We show that the hypothesis of an extended spherical excess emission with a uniform energy spectrum is compatible with the Fermi -LAT data in our region of interest at 95% CL. Assuming that this excess is the extended counterpart of the one seen in the inner few degrees of the Galaxy, we derive a lower limit of 10.0 • (95% CL) on its extension away from the GC. We show that, in light of the large correlated uncertainties that affect the subtraction of the Galactic diffuse emission in the relevant regions, the energy spectrum of the excess is equally compatible with both a simple broken power-law of break energy E break = 2.1 ± 0.2 GeV, and with spectra predicted by the self-annihilation of dark matter, implying in the case ofbb final states a dark matter mass of m χ = 49 +6.4 −5.4 GeV.The study of Galactic cosmic rays (CRs) and gamma-ray physics has been a very active field in the last few decades with the launch of PAMELA [1, 2], AMS-02 [3] aboard the International Space Station (ISS) and, in particular, of the Large Area Telescope (LAT) aboard the Gamma-Ray Space Telescope (Fermi ) [4]. The latter has produced the most detailed maps of the gamma-ray sky ever, in a wide energy range and with good energy and angular resolution [5]. The interaction of Galactic CRs with the interstellar medium (ISM) results in the diffuse emission from the Milky Way, which is the brightest source of gamma rays seen with the Fermi -LAT. Thus, the Fermi -LAT data provide an important handle for understanding the origin and the propagation of CRs in our Galaxy. This is complemented by measurements in microwaves [6,7], X-rays [8], lower energy [9] and higher energy gamma rays [10][11][12], and neutrinos [13].More specifically, focused studies of known Galactic sources in gamma rays by both the Fermi -LAT and Atmospheric Cherenkov Telescopes (ACTs), together with measurements in X-rays, microwaves and now neutrinos, have helped us in studying and modeling the source properties and the primary CRs composition injected [14-22] by for example supernova remnants (SNRs) and pulsars. Moreover, the analysis of gamma-ray data has led ...

Several groups have identified an extended excess of gamma rays over the modeled foreground and background emissions towards the Galactic center (GC) based on observations with the Fermi Large Area Telescope. This excess emission is compatible in morphology and spectrum with a telltale sign from dark matter (DM) annihilation. Here, we present a critical reassessment of DM interpretations of the GC signal in light of the foreground and background uncertainties that some of us recently outlaid in Calore et al. 2014. We find that a much larger number of DM models fits the gamma-ray data than previously noted. In particular: (1) In the case of DM annihilation intobb, we find that even large DM masses up to mχ 74 GeV are allowed at p-value > 0.05. (2) Surprisingly, annihilation into non-relativistic hh gives a good fit to the data. (3) The inverse Compton emission from µ + µ − with mχ ∼ 60-70 GeV can also account for the excess at higher latitudes, |b| > 2 • , both in its spectrum and morphology. We also present novel constraints on a large number of mixed annihilation channels, including cascade annihilation involving hidden sector mediators. Finally, we show that the current limits from dwarf spheroidal observations are not in tension with a DM interpretation when uncertainties on the DM halo profile are accounted for. PACS numbers: 95.30.Cq,95.35+d,95.85.Pw,

International audienceStellar-mass primordial black holes (PBH) have been recently reconsidered as a dark matter (DM) candidate after the aLIGO discovery of several binary black hole (BH) mergers with masses of tens of M⊙. Matter accretion on such massive objects leads to the emission of high-energy photons, capable of altering the ionization and thermal history of the universe. This, in turn, affects the statistical properties of the cosmic microwave background (CMB) anisotropies. Previous analyses have assumed spherical accretion. We argue that this approximation likely breaks down and that an accretion disk should form in the dark ages. Using the most up-to-date tools to compute the energy deposition in the medium, we derive constraints on the fraction of DM in PBH. Provided that disks form early on, even under conservative assumptions for accretion, these constraints exclude a monochromatic distribution of PBH with masses above ∼2  M⊙ as the dominant form of DM. The bound on the median PBH mass gets more stringent if a broad, log-normal mass function is considered. A deepened understanding of nonlinear clustering properties and BH accretion disk physics would permit an improved treatment and possibly lead to more stringent constraints