Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of Gamma-ray Emission from M31 via FERMI-LAT   2 years worth of archival FERMI-LAT data was used to search for the gamma-ray
emission from the Andromeda galaxy. The data show no noticeable elliptical
image. Subsequent on-off source aperture photometry analysis using a CO image
template show a 7 sigma excess in the number of on-source apertures in
comparison to the off-source apertures, yielding a flux of (4.95+/-0.71)x10-8
photons cm-2 s-1 for E>100 MeV.

8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
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
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ