Alexander V. Belikov

Searching For Dark Matter Subhalos In the Fermi-LAT Second Source Catalog

The dark matter halo of the Milky Way is expected to contain an abundance of smaller subhalos. These subhalos can be dense and produce potentially observable fluxes of gamma rays. In this paper, we search for dark matter subhalo candidates among the sources in the Fermi-LAT Second Source Catalog which are not currently identified or associated with counterparts at other wavelengths. Of the nine high-significance, high-latitude (|b|>60 degrees), non-variable, unidentified sources contained in this catalog, only one or two are compatible with the spectrum of a dark matter particle heavier than approximately 50-100 GeV. The majority of these nine sources, however, feature a spectrum that is compatible with that predicted from a lighter (~5-40 GeV) dark matter particle. This population is consistent with the number of observable subhalos predicted for a dark matter candidate in this mass range and with an annihilation cross section of a simple thermal relic (sigma v~3x10^{-26} cm^3/s). Observations in the direction of these sources at other wavelengths will be necessary to either reveal their astrophysical nature (as blazars or other active galactic nuclei, for example), or to further support the possibility that they are dark matter subhalos by failing to detect any non-gamma ray counterpart.

The Isotropic Radio Background and Annihilating Dark Matter

Observations by ARCADE-2 and other telescopes sensitive to low frequency radiation have revealed the presence of an isotropic radio background with a hard spectral index. The intensity of this observed background is found to exceed the ux predicted from astrophysical sources by a factor of approximately 5-6. In this article, we consider the possibility that annihilating dark matter particles provide the primary contribution to the observed isotropic radio background through the emission of synchrotron radiation from electron and positron annihilation products. For reasonable estimates of the magnetic elds present in clusters and galaxies, we nd that dark matter could potentially account for the observed radio excess, but only if it annihilates mostly to electrons and/or muons, and only if it possesses a mass in the range of approximately 5-50 GeV. For such models, the annihilation cross section required to normalize the synchrotron signal to the observed excess is v (0:4 30) 10 26 cm 3 /s, similar to the value predicted for a simple thermal relic (v 3 10 26 cm 3 /s). We nd that in any scenario in which dark matter annihilations are responsible for the observed excess radio emission, a signicant fraction of the isotropic gamma ray background observed by Fermi must result from dark matter as well.

Study of the Gamma-ray Spectrum from the Galactic Center in view of Multi-TeV Dark Matter Candidates

Motivated by the complex gamma-ray spectrum of the Galactic Center source now measured over five decades in energy, we revisit the issue of the role of dark matter annihilations in this interesting region. We reassess whether the emission measured by the HESS collaboration could be a signature of dark matter annihilation, and we use the {\em Fermi} LAT spectrum to model the emission from SgrA*, using power-law spectral fits. We find that good fits are achieved by a power law with an index

Equivalence principle violation in weakly Vainshtein-screened systems

\sim 2.5-2.6

Diffuse gamma ray background from annihilating dark matter in density spikes around supermassive black holes

, in combination with a spectrum similar to the one observed from pulsar population and with a spectrum from a

Study of the very high energy gamma-ray spectrum from the Galactic Center and future prospects

\gsi10

Superexponential Cutoff as a Probe of Annihilating Dark Matter

TeV DM annihilating to a mixture of

How dark matter reionized the Universe

b{\bar b}

CoGeNT, DAMA, and Neutralino Dark Matter in the Next-To-Minimal Supersymmetric Standard Model

and harder

Constraining cosmological dark matter annihilation with gamma ray observations

\tau^+ \tau^-