Related papers: The nature of the Diffuse Gamma-Ray Background
We study the annihilating dark matter contribution to the extra-galactic diffuse gamma-ray background spectrum, motivated by the recent observations of cosmic-ray positron/electron anomalies. The observed diffuse gamma-ray flux provides…
The Fermi gamma-ray satellite has recently detected gamma-ray emissions from radio galaxy cores. From these samples, we first examine the correlation between the luminosities at 5 GHz, L_{5GHz}, and at 0.1-10 GeV, L_{gamma}, of these…
We study the origin of the extragalactic diffuse gamma-ray background using the data from the Fermi telescope. To estimate the background level, we count photons at high Galactic latitudes |b|>60 degrees. Subtracting photons associated to…
We measured the dipole of the diffuse $\gamma$-ray background (DGB) identifying a highly significant time-independent signal coincidental with that of the Pierre Auger UHECR. The DGB dipole is determined from flux maps in narrow energy…
The deepest observations of the X-ray background approach the surface brightness of the truly diffuse component generated by Thomson scattering of cosmic X-ray photons. Available estimates of the electron density and the X-ray luminosity…
The Fermi-LAT telescope has measured the extragalactic gamma-ray background (EGB) generated by the ensemble of all extragalactic sources. The energy distribution of the EGB is well described as a power-law with a spectral index…
Recent observations of the diffuse Galactic gamma-ray emission by the Fermi-LAT satellite have shown significant deviations from models which assume the same diffusion properties for cosmic rays (CR) throughout the Galaxy. We explore the…
The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma-Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray…
The deep X-ray surveys performed by the two major X-ray observatories on flight, Chandra and XMM, are being resolving the bulk of the cosmic X-ray background (XRB) in the 2-10 keV energy band, where the sky flux is dominated by…
We calculate the diffuse $\gamma$-ray emission due to the population of misaligned AGN (MAGN) unresolved by the Large Area Telescope (LAT) on the {\it Fermi} Gamma-ray Space Telescope ({\it Fermi}). A correlation between the $\gamma$-ray…
Dark matter annihilation in Galactic substructure produces diffuse gamma-ray emission of remarkably constant intensity across the sky, and in general this signal dominates over the smooth halo signal at angles greater than a few tens of…
Measurement of the extragalactic background (EGBR) of diffuse gamma-rays is perhaps one of the most challenging tasks for future gamma-ray observatories, such as GLAST. This is because any determination will depend on accurate subtraction…
The Universe is largely transparent to $\gamma$ rays in the GeV energy range, making these high-energy photons valuable for exploring energetic processes in the cosmos. After seven years of operation, the Fermi {\it Gamma-ray Space…
I report on progress in my ongoing work with Professor Jayant Murthy concerning the origin and nature of the diffuse ultraviolet background radiation over the sky. We have obtained and are reducing a vast trove of Voyager ultraviolet…
We construct empirical models of the diffuse gamma-ray background toward the Galactic Center. Including all known point sources and a template of emission associated with interactions of cosmic rays with molecular gas, we show that the…
It has been suggested that unresolved radio galaxies and radio quasars (sometimes referred to as misaligned active galactic nuclei) could be responsible for a significant fraction of the observed diffuse gamma-ray background. In this study,…
The origin of the cosmic gamma-ray background (CGB) is a longstanding mystery in high-energy astrophysics. Possible candidates include ordinary astrophysical objects such as unresolved blazars, as well as more exotic processes such as dark…
The Extragalactic Background Light (EBL) from the infrared (IR) through the ultraviolet (UV) is dominated by emission from stars, either directly or through absorption and reradiation by dust. It can thus give information on the star…
Active galactic nuclei (AGN) with jets seen at small viewing angles are the most luminous and abundant objects in the $\gamma$-ray sky. AGN with jets misaligned along the line-of-sight appear fainter in the sky, but are more numerous than…
We report on the first Fermi Large Area Telescope (LAT) measurements of the so-called "extra-galactic" diffuse gamma-ray emission (EGB). This component of the diffuse gamma-ray emission is generally considered to have an isotropic or nearly…