Can Galactic γ-Ray Background be due to Superposition of γ-Rays from Millisecond Pulsars?

1998 ◽  
Vol 188 ◽  
pp. 273-274
Author(s):  
V.B. Bhatia ◽  
S. Mishra ◽  
N. Panchapakesan
Keyword(s):  
Cosmic Rays ◽  
Cosmic Ray ◽  
Diffuse Radiation ◽  
High Energy ◽  
Molecular Gas ◽  
Inverse Compton Scattering ◽  
High Energy Electrons ◽  
Inverse Compton ◽  
Γ Rays ◽  
Γ Ray

The SAS 2 and COS B observations have established the existence of diffuse γ-rays in our Galaxy in various energy ranges. The diffuse radiation is attributed to the interaction of cosmic ray nuclei and electrons with the particles of interstellar atomic and molecular gas (via the decay of pions and bremsstrahlung, respectively). Inverse Compton scattering of interstellar photons by the high energy electrons of cosmic rays may also be contributing to this background. In addition some contribution may come from discrete sources of γ-rays.

scholarly journals Particle Acceleration in Extragalactic Jets and Implications for the High-Energy Emission from Blazars

1994 ◽  
Vol 159 ◽  
pp. 29-32
Author(s):  
R. Schlickeiser ◽  
C. D. Dermer
Keyword(s):  
Compton Scattering ◽  
Accretion Disk ◽  
High Energy ◽  
Relativistic Electrons ◽  
Spectral Evolution ◽  
Inverse Compton Scattering ◽  
Central Engine ◽  
Inverse Compton ◽  
Γ Rays ◽  
Γ Ray

We demonstrate that the prevalence of superluminal sources in the sample of γ-ray blazars and the peak of their luminosity spectra at γ-ray energies can be readily explained if the γ-rays result from the inverse Compton scattering of the accretion disk radiation by relativistic electrons in outflowing plasam jets. Compton scattering of external radiation by nonthermal particles in blazar jets is dominated by accretion disk photons rather than scattered radiation to distances of ∼ 0.01–0.1 pc from the central engine for standard parameters. The size of the γ-ray photosphere and the spectral evolution of the relativistic electron spectra constrain the location of the acceleration and emission sites in these objects.

High-energy γ rays of cosmic origin

1968 ◽  
Vol 46 (10) ◽  
pp. S484-S487 ◽  
Author(s):  
K. C. Anand ◽  
R. R. Daniel ◽  
S. A. Stephens
Keyword(s):  
Cosmic Ray ◽  
High Energy ◽  
X Rays ◽  
Inverse Compton Scattering ◽  
Upper Limits ◽  
Inverse Compton ◽  
Geomagnetic Cutoff ◽  
Γ Rays ◽  
Residual Air ◽  
Cosmic Origin

A stack of nuclear emulsions flown over Hyderabad (vertical geomagnetic cutoff rigidity 16.9 GV), India, under 6 g/cm2 of residual air has been used to set upper limits to the flux of γ rays of cosmic origin. The integral flux values obtained are 13 × 10−4, 6 × 10−4, 2.6 × 10−4, 1.4 × 10−4, 0.6 × 10−4, and 0.3 × 10−4 photons (em2 s sr)−1 for energies greater than 50 MeV, 100 MeV, 2 GeV, 5 GeV, 10 GeV, and 50 GeV respectively. Using these data and those of Kraushaar et al. (1965), it seems unlikely that cosmic-ray collisions in meta-galactic space can be an important source of electrons needed to explain the finite flux of cosmic X rays as due to the inverse Compton scattering of these electrons with photons of the universal blackbody radiation at 3 °K; such collisions would predict a flux of γ rays much in excess of the upper limits obtained in the energy region 50–100 MeV.

scholarly journals Cosmic rays and high energy emission from starburst galaxies

2011 ◽  
Vol 7 (S284) ◽  
pp. 393-396
Author(s):  
Brian C. Lacki ◽  
Todd A. Thompson
Keyword(s):  
Cosmic Rays ◽  
High Energy ◽  
Starburst Galaxies ◽  
Electron Cooling ◽  
X Ray ◽  
Inverse Compton ◽  
Γ Rays ◽  
Γ Ray ◽  
High Energy Emission ◽  
The Magnetic Field

AbstractThe nearby starburst galaxies M82 and NGC 253 are now detected in GeV and TeV γ-rays, allowing us to directly study cosmic rays (CRs) in starburst galaxies. Combined with radio observations, the detections constrain the propagation and density of CRs in these starbursts. We discuss the implications for “proton calorimetry”, whether CR protons cool through pion losses before escaping these galaxies. The ratio of γ-ray and radio luminosities constrains how much of the CR electron cooling is due to synchrotron losses. As for leptonic emission, we predict that synchrotron and Inverse Compton emission make up ~1–10% of the unresolved hard X-ray emission from M82, and a few percent or less of the total X-ray emission from starbursts. A detection of these components would inform us of the magnetic field strength and 10 – 100 TeV electron spectrum. We conclude by discussing the prospects for detecting leptonic MeV γ-rays from starbursts and the cosmic γ-ray background.

scholarly journals Molecular Clouds Observed by the EGRET Gamma-Ray Telescope

1997 ◽  
Vol 170 ◽  
pp. 22-24 ◽  
Author(s):  
Seth. W. Digel ◽  
Stanley D. Hunter ◽  
Reshmi Mukherjee ◽  
Eugéne J. de Geus ◽  
Isabelle A. Grenier ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Molecular Clouds ◽  
Gamma Ray ◽  
Angular Resolution ◽  
Cosmic Ray ◽  
High Energy ◽  
Background Rejection ◽  
Γ Rays ◽  
Γ Ray ◽  
Production Mechanisms

EGRET, the high-energy γ-ray telescope on the Compton Gamma-Ray Observatory, has the sensitivity, angular resolution, and background rejection necessary to study diffuse γ-ray emission from the interstellar medium (ISM). High-energy γ rays produced in cosmic-ray (CR) interactions in the ISM can be used to determine the CR density and calibrate the CO line as a tracer of molecular mass. Dominant production mechanisms for γ rays of energies ∼30 MeV–30 GeV are the decay of pions produced in collisions of CR protons with ambient matter and Bremsstrahlung scattering of CR electrons.

scholarly journals Very High Energy γ-Ray Generation Near The Light Cylinder of an Axisymmetric Rotator: Cos-B Like γ-Ray Sources

1992 ◽  
Vol 128 ◽  
pp. 207-208
Author(s):  
S. V. Bogovalov ◽  
YU. D. Kotov
Keyword(s):  
High Energy ◽  
Relativistic Electrons ◽  
X Rays ◽  
Inverse Compton Scattering ◽  
Light Cylinder ◽  
Radiation Spectra ◽  
Inverse Compton ◽  
Very High Energy ◽  
Γ Ray ◽  
Very High

AbstractSuper-hard γ-ray radiation spectra have been calculated. This radiation is generated near the velocity-of-light cylinder through the process of inverse-Compton scattering of relativistic electrons by thermal photons radiated by a neutron star. These calculations have been compared with observations of the Crab and Vela pulsars at 1000-GeV γ-ray energies. A correlation between γ-ray flares and those in soft (Ex ≃ lkeV) X-rays are predicted.

scholarly journals Gamma Rays from Cosmic Rays

1981 ◽  
Vol 94 ◽  
pp. 309-319 ◽  
Author(s):  
A. W. Wolfendale
Keyword(s):  
Cosmic Rays ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity ◽  
Cosmic Ray Interactions ◽  
The Galaxy ◽  
Γ Rays ◽  
Γ Ray

It is shown that there is evidence favouring molecular clouds being sources of γ-rays, the fluxes being consistent with expectation for ambient cosmic rays interacting with the gas in the clouds for the clouds considered. An estimate is made of the fraction of the apparently diffuse γ-ray flux which comes from cosmic ray interactions in the I.S.M. as distinct from unresolved discrete sources. Finally, an examination is made of the possibility of gradients of cosmic ray intensity in the Galaxy.

scholarly journals Very high energy cosmic gamma rays

1965 ◽  
Vol 23 ◽  
pp. 253-258
Author(s):  
M. Libber ◽  
S. N. Milford ◽  
M. S. Spergel
Keyword(s):  
Pion Production ◽  
Center Of Mass ◽  
Cosmic Ray ◽  
High Energy ◽  
Mass System ◽  
Proton Proton ◽  
Production Spectrum ◽  
Very High Energy ◽  
Γ Rays ◽  
Γ Ray

Collisions of high energy cosmic rays with intergalactic gas produce various secondaries, including neutral pions that decay into high energy γ rays. The Landau-Milekhin hydrodynamical model for proton-proton collisions is used to calculate the pion production spectrum corresponding to cosmic γ rays of energy above 10 Gev. A source function for these high energy γ rays in space is found by combining the pion production and decay spectra with the primary cosmic ray proton flux. The resulting γ ray spectrum follows a different power law than spectra based upon the usual assumption of a line spectrum for the pions in the center of mass system of the colliding protons. The high energy γ ray intensity in space is calculated for a simple model universe. By comparison with previous estimates for the proton photoproduction process, it is found that proton-proton and proton-photon collisions appear to contribute about the same order of magnitude to the intergalactic γ ray intensity above ∼1016 eV.

Particle Acceleration in the Disk-Halo System

1991 ◽  
Vol 144 ◽  
pp. 377-386
Author(s):  
Reinhard Schlickeiser
Keyword(s):  
Particle Acceleration ◽  
Cosmic Rays ◽  
Cosmic Ray ◽  
Energy Spectra ◽  
Galactic Wind ◽  
Γ Rays ◽  
Γ Ray

The recent observations of the nonthermal properties of the halo of our Galaxy at radio and γ-ray wavelengths are summarized. Radio and γ-ray data show a similar spectral flattening with Galactic height towards the anticenter direction, which is interpreted as a cosmic-ray effect. Several theoretical explanations for the flattening of the energy spectra of the radiating cosmic-ray electrons (in the radio) and nucleons (in γ-rays) are reviewed including propagation of cosmic rays in an accelerating Galactic wind and the presence of cosmic-ray sources with flat energy spectra in the halo.

NUCLEAR PHOTON SCIENCE WITH INVERSE-COMPTON SCATTERING

2009 ◽  
Vol 18 (10) ◽  
pp. 1970-1975
Author(s):  
MAMORU FUJIWARA
Keyword(s):  
Materials Science ◽  
Nuclear Reactions ◽  
Short Pulse ◽  
Medical Science ◽  
High Energy ◽  
Hadron Structure ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Γ Ray ◽  
New Research

Recent developments of the synchroton radiation facilities and intense lasers are now guiding us to a new research frontier with probes of a high energy GeV photon beam and an intense and short pulse MeV γ-ray beam. New directions of the science developments with photo-nuclear reactions are discussed. The inverse Compton γ -ray has two good advantages for searching for a microscopic quantum world; they are 1) good emmitance and 2) high linear and circular polarizations. With these advantages, photon beams in the energy range from MeV to GeV are used for studying hadron structure, nuclear structure, astrophysics, materials science, as well as for applying medical science.

scholarly journals Cosmic-Ray induced diffuse emissions from the Milky Way and Local Group galaxies

2011 ◽  
Vol 7 (S284) ◽  
pp. 360-364
Author(s):  
Troy A. Porter
Keyword(s):  
Cosmic Rays ◽  
Interstellar Medium ◽  
Milky Way ◽  
Spectral Energy Distribution ◽  
Cosmic Ray ◽  
High Energy ◽  
Spectral Energy ◽  
Entire Volume ◽  
Γ Rays ◽  
Diffuse Emissions

AbstractCosmic rays fill up the entire volume of galaxies, providing an important source of heating and ionisation of the interstellar medium, and may play a significant role in the regulation of star formation and galactic evolution. Diffuse emissions from radio to high-energy γ-rays (>100 MeV) arising from various interactions between cosmic rays and the interstellar medium, interstellar radiation field, and magnetic field, are currently the best way to trace the intensities and spectra of cosmic rays in the Milky Way and other galaxies. In this contribution, I describe our recent work to model the full spectral energy distribution of galaxies like the Milky Way from radio to γ-ray energies. The application to other galaxies, in particular the Magellanic Clouds and M31 that are now resolved in high-energy γ-rays by the Fermi-LAT, is also discussed.

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