593 research outputs found
Gamma-Ray Observations of the Interstellar Clouds in Cepheus
During the last six months of the period of performance, the diffuse gamma-ray emission from the Monoceros region was reanalyzed and one of the important conclusions was revised as a result. The reanalysis incorporated newly-available data from recent EGRET viewing periods and revealed a previously-uncataloged gamma-ray point source near the plane in Monoceros. The effect of incorporating this source in the diffuse emission model was significant, as its flux was comparable to that from a large interstellar cloud complex in the Perseus arm. In the updated model, a greatly reduced gamma-ray emissivity was found in the Perseus arm. This finding alters the previous conclusion that we had found evidence for an enhanced emissivity in the arm, which had supported the hypothesis that cosmic rays are coupled to the interstellar medium on the scale of spiral arms. Our updated findings are consistent with our previous results for the emissivity toward the Cepheus region (Digel et al. 1996), where a monotonic gradient of emissivity in the outer Galaxy was found. The updated analysis of Monoceros was presented at the June, 1998 meeting of the American Astronomical Society, and a journal publication should be ready for submission soon
What can GLAST say about the origin of cosmic rays in other galaxies ?
Gamma rays in the band from 20 MeV to 300 GeV, used in combination with data
from radio and X-ray bands, provide a powerful tool for studying the origin of
cosmic rays in our sister galaxies Andromeda and the Magellanic Clouds.
Gamma-ray Large Area Space Telescope (GLAST) will spatially resolve these
galaxies and measure the spectrum and intensity of diffuse gamma radiation from
the collisions of cosmic rays with gas and dust in them. Observations of
Andromeda will give an external perspective on a spiral galaxy like the Milky
Way. Observations of the Magellanic Clouds will permit a study of cosmic rays
in dwarf irregular galaxies, where the confinement is certainly different and
the massive star formation rate is much greater.Comment: 4 pages including 6 figures; to appear in Proc. ACE-2000 Symp. "The
Acceleration and Transport of Energetic Particles Observed in the
Heliosphere" (Jan. 5-8, 2000, Indian Wells, CA), AIP Conf. Proc. More details
can be found at the LHEA GLAST page at
http://lhea-glast.gsfc.nasa.gov/pub/science/index.htm
A future very-high-energy view of our Galaxy
The survey of the inner Galaxy with H.E.S.S. was remarkably successful in
detecting a wide range of new very-high-energy gamma-ray sources. New TeV
gamma-ray emitting source classes were established, although several of the
sources remain unidentified, and progress has been made in understanding
particle acceleration in astrophysical sources. In this work, we constructed a
model of a population of such very-high-energy gamma-ray emitters and
normalised the flux and size distribution of this population model to the
H.E.S.S.-discovered sources. Extrapolating that population of objects to lower
flux levels we investigate what a future array of imaging atmospheric
telescopes (IACTs) such as AGIS or CTA might detect in a survey of the Inner
Galaxy with an order of magnitude improvement in sensitivity. The sheer number
of sources detected together with the improved resolving power will likely
result in a huge improvement in our understanding of the populations of
galactic gamma-ray sources. A deep survey of the inner Milky Way would also
support studies of the interstellar diffuse gamma-ray emission in regions of
high cosmic-ray density. In the final section of this paper we investigate the
science potential for the Galactic Centre region for studying energy-dependent
diffusion with such a future array.Comment: Proceeding of "Heidelberg International Symposium on High Energy
Gamma-Ray Astronomy", held in Heidelberg, 7-11 July 2008, submitted to AIP
Conference Proceedings. 4 pages, 4 figure
Multi-wavelength constraints on cosmic-ray leptons in the Galaxy
Cosmic rays (CRs) interact with the gas, the radiation field and the magnetic
field in the Milky Way, producing diffuse emission from radio to gamma rays.
Observations of this diffuse emission and comparison with detailed predictions
are powerful tools to unveil the CR properties and to study CR propagation. We
present various GALPROP CR propagation scenarios based on current CR
measurements. The predicted synchrotron emission is compared to radio surveys,
and synchrotron temperature maps from WMAP and Planck, while the predicted
interstellar gamma-ray emission is compared to Fermi-LAT observations. We show
how multi-wavelength observations of the Galactic diffuse emission can be used
to help constrain the CR lepton spectrum and propagation. Finally we discuss
how radio and microwave data could be used in understanding the diffuse
Galactic gamma-ray emission observed with Fermi-LAT, especially at low
energies.Comment: 8 pages, 5 figures; in Proceedings of the 34th International Cosmic
Ray Conference (ICRC 2015), The Hague (The Netherlands); Oral contributio
The Origin of Cosmic Rays and the Diffuse Galactic Gamma-Ray Emission
Cosmic-ray interactions with interstellar gas and photons produce diffuse
gamma-ray emission. In this talk we will review the current understanding of
this diffuse emission and its relationship to the problem of the origin of
cosmic rays. We will discuss the open issues and what progress might be
possible with GLAST, which is planned for launch in 2006.Comment: 10 pages, 5 figures. Invited talk at the "Gamma 2001" Symp., April
4-6, 2001, Baltimore, MD. AIP Conf. Proc. v.587, eds. S. Ritz, N. Gehrels, &
C. R. Shrader, in pres
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