  We present multi-wavelength observations (from optical to sub-millimeter,
including Spitzer and SCUBA) of H2XMMJ 003357.2-120038 (also GD158_19), an
X-ray selected, luminous narrow-line (Type 2) quasar at z=1.957 selected from
the HELLAS2XMM survey. Its broad-band properties can be reasonably well modeled
assuming three components: a stellar component to account for the optical and
near-IR emission, an AGN component (i.e., dust heated by an accreting active
nucleus), dominant in the mid-IR, with an optical depth at 9.7 micron along the
line of sight (close to the equatorial plane of the obscuring matter) of
tau(9.7)=1 and a full covering angle of the reprocessing matter (torus) of 140
degrees, and a far-IR starburst component (i.e., dust heated by star formation)
to reproduce the wide bump observed longward of 70 micron. The derived
star-formation rate is about 1500 solar masses per year. The overall modeling
indicates that GD158_19 is a high-redshift X-ray luminous, obscured quasar with
coeval powerful AGN activity and intense star formation. It is probably caught
before the process of expelling the obscuring gas has started, thus quenching
the star formation.
