The redshift and broad band spectral energy distribution of NRAO 150
  Context. NRAO 150 is one of the brightest radio and mm AGN sources on the
northern sky. It has been revealed as an interesting source where to study
extreme relativistic jet phenomena. However, its cosmological distance has not
been reported so far, because of its optical faintness produced by strong
Galactic extinction.
  Aims. Aiming at measuring the redshift of NRAO 150, and hence to start making
possible quantitative studies from the source.
  Methods. We have conducted spectroscopic and photometric observations of the
source in the near-IR, as well as in the optical.
  Results. All such observations have been successful in detecting the source.
The near-IR spectroscopic observations reveal strong H$\alpha$ and H$\beta$
emission lines from which the cosmological redshift of NRAO 150
($z=1.517\pm0.002$) has been determined for the first time. We classify the
source as a flat-spectrum radio-loud quasar, for which we estimate a large
super-massive black-hole mass $\sim5\times 10^{9} \mathrm{M_\odot}$. After
extinction correction, the new near-IR and optical data have revealed a
high-luminosity continuum-emission excess in the optical (peaking at
$\sim2000$\,\AA, rest frame) that we attribute to thermal emission from the
accretion disk for which we estimate a high accretion rate, $\sim30$\,% of the
Eddington limit.
  Conclusions. Comparison of these source properties, and its broad-band
spectral-energy distribution, with those of Fermi blazars allow us to predict
that NRAO 150 is among the most powerful blazars, and hence a high luminosity
-although not detected yet- $\gamma$-ray emitter.
