Stellar population models in the UV

I. Characterisation of the New Generation Stellar Library^⋆

¹ Instituto de Astrofísica de Canarias, La Laguna, 38200 Tenerife, Spain
e-mail: mina.koleva@gmail.com
² Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain
³ Université Lyon 1, Villeurbanne, 69622, France; CRAL, Observatoire de Lyon, 69561, St. Genis Laval, CNRS, UMR 5574, France
⁴ Sterrenkundig Observatorium, Ghent University, Krijgslaan 281, S9, 9000 Ghent, Belgium

Received: 10 September 2011
Accepted: 27 October 2011

Abstract

Context. 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.

Aims. 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.

Methods. For our analyses we used ULySS, a full spectrum fitting package, fitting the NGSL spectra against the MILES interpolator.

Results. 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 Å in the UV to 10 Å in the near-infrared (NIR), corresponding to a roughly constant reciprocal resolution R = λ/δλ ≈ 1000 and an instrumental velocity dispersion σ_ins ≈ 130 km s^-1. We derived the atmospheric parameters homogeneously. The precision for the FGK stars is 42 K, 0.24 and 0.09 dex for T_eff, log    g and [Fe/H], respectively. The corresponding mean errors are 29 K, 0.50 and 0.48 dex for the M stars, 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.