Diffuse interstellar bands in RAVE survey spectra^*

¹ INAF Osservatorio Astronomico di Padova, Asiago, Italy e-mail: ulisse.munari@oapd.inaf.it
² Observatoire de Strasbourg, Strasbourg, France
³ Rudolf Pierls Center for Theoretical Physics, University of Oxford, UK
⁴ Institute of Astronomy, School of Physics, University of Sydney, Australia
⁵ Astrophysikalisches Institut Potsdam, Potsdam, Germany
⁶ Macquarie University, Sidney, Australia
⁷ RSAA Mount Stromlo Observatory, Camberra, Australia
⁸ University of Central Lancashire, Preston, UK
⁹ Institute of Astronomy, University of Cambridge, UK
¹⁰ Astronomisches Rechen-Institut, Center for Astronomy of the University of Heidelberg, Heidelberg, Germany
¹¹ University of Groningen, Groningen, The Netherlands
¹² University of Victoria, Victoria, Canada
¹³ e2v Centre for Electronic Imaging, School of Engineering and Design, Brunel University, Uxbridge, UK
¹⁴ Anglo Australian Observatory, Sydney, Australia
¹⁵ Johns Hopkins University, Baltimore, Maryland, USA
¹⁶ Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia

Received: 21 May 2008
Accepted: 9 July 2008

Abstract

We have used spectra of hot stars from the RAVE Survey in order to investigate the visibility and properties of five diffuse interstellar bands previously reported in the literature. The RAVE spectroscopic survey for Galactic structure and kinematics records CCD spectra covering the 8400–8800 Å wavelength region at 7500 resolving power. The spectra are obtained with the UK Schmidt at the AAO, equipped with the 6dF multi-fiber positioner. The DIB at 8620.4 Å is by far the strongest and cleanest of all DIBs occurring within the RAVE wavelength range, with no interference by underlying absorption stellar lines in hot stars. It correlates so tightly with reddening that it turns out to be a reliable tool to measure it, following the relation (Å), valid throughout the general interstellar medium of our Galaxy. The presence of a DIB at 8648 Å is confirmed. Its intensity appears unrelated to reddening, in agreement with scanty and preliminary reports available in the literature, and its measurability is strongly compromised by severe blending with underlying stellar He I doublet at 8649 Å. The two weak DIBs at 8531 and 8572 Å do not appear real and should actually be blends of underlying stellar lines. The very weak DIB at 8439 Å cannot be resolved within the profile of the much stronger underlying hydrogen Paschen 18 stellar line.