Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Detection of the Small Magellanic Cloud in gamma-rays with Fermi/LAT   The flux of gamma rays with energies >100MeV is dominated by diffuse emission
from CRs illuminating the ISM of our Galaxy through the processes of
Bremsstrahlung, pion production and decay, and inverse-Compton scattering. The
study of this diffuse emission provides insight into the origin and transport
of CRs. We searched for gamma-ray emission from the SMC in order to derive
constraints on the CR population and transport in an external system with
properties different from the Milky Way. We analysed the first 17 months of
continuous all-sky observations by the Large Area Telescope of the Fermi
mission to determine the spatial distribution, flux and spectrum of the
gamma-ray emission from the SMC. We also used past radio synchrotron
observations of the SMC to study the population of CR electrons specifically.
We obtained the first detection of the SMC in high-energy gamma rays, with an
integrated >100MeV flux of (3.7 +/-0.7) x10e-8 ph/cm2/s, with additional
systematic uncertainty of <16%. The emission is steady and from an extended
source ~3{\deg} in size. It is not clearly correlated with the distribution of
massive stars or neutral gas, nor with known pulsars or SNRs, but a certain
correlation with supergiant shells is observed. The observed flux implies an
upper limit on the average CR nuclei density in the SMC of ~15% of the value
measured locally in the Milky Way. The population of high-energy pulsars of the
SMC may account for a substantial fraction of the gamma-ray flux, which would
make the inferred CR nuclei density even lower. The average density of CR
electrons derived from radio synchrotron observations is consistent with the
same reduction factor but the uncertainties are large. From our current
knowledge of the SMC, such a low CR density does not seem to be due to a lower
rate of CR injection and rather indicates a smaller CR confinement volume
characteristic size.

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The categories of this paper are: ao-sci
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The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
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The categories of this paper are: q-alg
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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
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The categories of this paper are: q-bio
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The categories of this paper are: dg-ga
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The categories of this paper are: cs
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The categories of this paper are: mtrl-th
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The categories of this paper are: gr-qc