The Gaia-ESO Survey: Tracing interstellar extinction

Context. Large spectroscopic surveys have in recent years enabled computing three-dimensional interstellar extinction maps thanks to the accurate stellar atmospheric parameters and line-of-sight distances these surveys provide. Interstellar extinction maps are complementary to 3D maps extracted from photometry and allow a more thorough studying of the dust properties.
Aims: Our goal is to use the high-resolution spectroscopic survey Gaia-ESO to obtain with a good distance resolution the interstellar extinction and its dependency as a function of the environment and the Galactocentric position.
Methods: We used the stellar atmospheric parameters of more than 5000 stars, obtained from the Gaia-ESO survey second internal data release, and combined them with optical (SDSS) and near-infrared (VISTA) photometry as well as different sets of theoretical stellar isochrones to calculate line-of-sight extinction and distances. The extinction coefficients were then compared with the literature to discuss their dependency on the stellar parameters and position in the Galaxy.
Results: Within the errors of our method, our work does not show any dependence of the interstellar extinction coefficient on the stellar atmospheric parameters. We find no evidence of a variation of E(J - H) /E(J - K) with the angle from the Galactic centre or with Galactocentric distance. This suggests that we are dealing with a uniform extinction law in the SDSS ugriz bands and the near-IR JHKs bands. Therefore, extinction maps built from mean colour-excesses that assume a constant extinction coefficient can be used without introducing any systematic errors.

Based on observations collected with the FLAMES spectrograph at the VLT/UT2 telescope (Paranal Observatory, ESO, Chile), for the Gaia-ESO Large Public Survey, programme 188.B-300.Appendix A is available in electronic form at http://www.aanda.org