Stellar population models in the UV: I. Characterisation of the New
  Generation Stellar Library
  The spectral predictions of stellar population models are not as accurate in
the ultra-violet (UV) as in the optical wavelength domain. One of the reasons
is the lack of high-quality stellar libraries. The New Generation Stellar
Library (NGSL), recently released,represents a significant step towards the
improvement of this situation. To prepare NGSL for population synthesis, we
determined the atmospheric parameters of its stars, we assessed the precision
of the wavelength calibration and characterised its intrinsic resolution. We
also measured the Galactic extinction for each of the NGSL stars. For our
analyses we used ULySS, a full spectrum fitting package, fitting the NGSL
spectra against the MILES interpolator. We find that the wavelength calibration
is precise up to 0.1 px, after correcting a systematic effect in the optical
range. The spectral resolution varies from 3{\AA} in the UV to 10{\AA} in the
near-infrared (NIR), corresponding to a roughly constant reciprocal resolution
R ~ 1000 and an instrumental velocity dispersion $\sigma_{ins}$ ~ 130 km/s. We
derived the atmospheric parameters homogeneously. The precision for the FGK
stars is 42K, 0.24 and 0.09 dex for Teff, logg and [Fe/H], respectively. The
corresponding mean errors are 29K, 0.50 and 0.48 dex for theMstars, and for the
OBA stars they are 4.5 percent, 0.44 and 0.18 dex. The comparison with the
literature shows that our results are not biased.
