Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the origin of soft X-rays in obscured AGN: answers from
  high-resolution spectroscopy with XMM-Newton   We present results of a high-resolution soft X-ray (0.2-2 keV) spectroscopic
study of a sample of 69 nearby obscured Active Galactic Nuclei (AGN) observed
with the Reflection Grating Spectrometer (RGS) on board XMM-Newton. This is the
largest sample ever studied with this technique so far. The main conclusions of
our study can be summarized as follows: a) narrow Radiative Recombination
Continua are detected in about 36% of the objects in our sample (in 26% their
intrinsic width is <10 eV); b) higher order transitions are generally enhanced
with respect to pure photoionization, indicating that resonant scattering plays
an important role in the ionization/excitation balance. These results support
the scenario, whereby the active nucleus is responsible for the X-ray ``soft
excess'' almost ubiquitously observed in nearby obscured AGN via
photoionization of circumnuclear gas. They confirm on a statistical basis the
conclusions drawn from the detailed study of the brightest spectra in the
sample. Furthermore, we propose a criterion to statistically discriminate
between AGN-photoionized sources and starburst galaxies, based on intensity of
the forbidden component of the OVII He-alpha triplet (once normalized to the
OVIII Ly-alpha) coupled with the integrated luminosity in He-like and H-like
oxygen lines.

1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex