Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Diffuse gamma-ray emission in the vicinity of young star cluster
  Westerlund 2   We report the results of our analysis of the publicly available data obtained
by the Large Area Telescope (LAT) on board of the Fermi satellite towards the
direction of the young massive star cluster Westerlund 2. We found significant
extended gamma-ray emission in the vicinity of Westerlund 2 with a hard
power-law energy spectrum extending from 1 GeV to 250 GeV with a photon index
of 2.0 +/- 0.1. We argue that amongst several alternatives, the luminous stars
in Westerlund 2 are likely sites of acceleration of particles responsible for
the diffuse gamma-ray emission of the surrounding interstellar medium. In
particular, the young star cluster Westerlund 2 can provide sufficient
non-thermal energy to account for the gamma-ray emission. In this scenario,
since the gamma-ray production region is significantly larger than the area
occupied by the star cluster, we conclude that the gamma-ray production is
caused by hadronic interactions of the accelerated protons and nuclei with the
ambient gas. In that case, the total energy budget in relativistic particles is
estimated of the order of 1e50 erg.

25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex