  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.

Astrophysics