  We present the Catalog of High REsolution Spectra of Obscured Sources
(CHRESOS) from the XMM-Newton Science Archive. It comprises the emission-line
luminosities of H- and He-like transitions from C to Si, and the Fe 3C and Fe
3G L-shell ones. Here, we concentrate on the soft X-ray OVII(f) and OVIII
Ly_alpha emission lines to shed light onto the physical processes with which
their formation can be related to: active galactic nucleus vs. star forming
regions. We compare their luminosity with that of two other important oxygen
key lines [OIII]5007A, in the optical, and [OIV]25.89mic, in the IR. We also
test OVII(f) and OVIIILy_alpha luminosities against that of continuum bands in
the IR and hard X-rays, which point to different ionization processes. We probe
into those processes by analyzing photoionization and colisional ionization
model predictions upon our lines. We show that both scenarios can explain the
formation and observed intensities of OVII(f) and OVIII Ly_alpha. By analyzing
the relationships between OVII(f) and OVIII Ly_alpha, and all other
observables: [OIII]5007A, [OIV]25.89mic emission lines, and MIR-12mic,
FIR-60mic, FIR-100mic, 2-10 keV and 14-195 keV continuum bands, we conclude
that the AGN radiation field is mainly responsible of the soft X-ray oxygen
excitation.
