An X-shooter composite of bright 1 < z < 2 quasars from UV to infrared
  Quasi-stellar object (QSO) spectral templates are important both to QSO
physics and for investigations that use QSOs as probes of intervening gas and
dust. However, combinations of various QSO samples obtained at different times
and with different instruments so as to expand a composite and to cover a wider
rest frame wavelength region may create systematic effects, and the
contribution from QSO hosts may contaminate the composite. We have constructed
a composite spectrum from luminous blue QSOs at 1 < z < 2.1 selected from the
Sloan Digital Sky Survey (SDSS). The observations with X-shooter simultaneously
cover ultraviolet (UV) to near- infrared (NIR) light, which ensures that the
composite spectrum covers the full rest-frame range from Ly$\beta$ to 11350
$\AA$ without any significant host contamination. Assuming a power-law
continuum for the composite we find a spectral slope of $\alpha_\lambda$ =
1.70+/-0.01, which is steeper than previously found in the literature. We
attribute the differences to our broader spectral wavelength coverage, which
allows us to effectively avoid fitting any regions that are affected either by
strong QSO emissions lines (e.g., Balmer lines and complex [Fe II] blends) or
by intrinsic host galaxy emission. Finally, we demonstrate the application of
the QSO composite spectrum for evaluating the reddening in other QSOs.
