Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The physical and chemical structure of Sagittarius B2 -- V. Non-thermal
  emission in the envelope of Sgr B2   The giant molecular cloud Sagittarius B2 (hereafter SgrB2) is the most
massive region with ongoing high-mass star formation in the Galaxy. In the
southern region of the 40-pc large envelope of SgrB2, we encounter the
SgrB2(DS) region which hosts more than 60 high-mass protostellar cores
distributed in an arc shape around an extended HII region. We use the Very
Large Array in its CnB and D configurations, and in the frequency bands C (4--8
GHz) and X (8--12 GHz) to observe the whole SgrB2 complex. Continuum and radio
recombination line maps are obtained. We detect radio continuum emission in
SgrB2(DS) in a bubble-shaped structure. From 4 to 12 GHz, we derive a spectral
index between -1.2 and -0.4, indicating the presence of non-thermal emission.
We decompose the contribution from thermal and non-thermal emission, and find
that the thermal component is clumpy and more concentrated, while the
non-thermal component is more extended and diffuse. The radio recombination
lines in the region are found to be not in local thermodynamic equilibrium
(LTE) but stimulated by the non-thermal emission. The thermal free-free
emission is likely tracing an HII region ionized by an O7 star, while the
non-thermal emission can be generated by relativistic electrons created through
first-order Fermi acceleration. We have developed a simple model of the
SgrB2(DS) region and found that first-order Fermi acceleration can reproduce
the observed flux density and spectral index.

29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio