EDIBLES: The ESO Diffuse Interstellar Bands Large Exploration Survey

EDIBLES is an ESO Large Program that used VLT/UVES to obtain a set of observations at high spectral resolution (R~80,000) from the near-UV to the near-IR, at a signal-to-noise ratio of ~1,000 per target, and this for ~120 Galactic targets that represent diffuse interstellar clouds with different physical conditions and dust properties. The aim is to fully characterize the interstellar sightlines to constrain the possible identifications of the specices responsible for the diffuse interstellar bands (DIBs), a set of more than 600 interstellar absorption lines that are mostly unidentified. EDIBLES collected data between 2014 and 2017; data exploitation is in progress.

EDIBLES is managed by an international team of researchers.

The main figure shows a synthetic spectrum of the DIBs as observed by toward the well-known target HD 183143 by Hobbs et al., 2009. There are currently more than 600 DIBs known, from the near-UV to the near-IR. They have a wide range of strengths and widths. Almost all of them are unidentified. The only exceptions are two strong DIBs (at 9577 and 9632AA, shown in the inset) and 3 weaker DIBs that are due to buckyball cations (C60+). The top left panel illustrates environmental behaviour of the DIBs: the fact that different DIBs respond differently to changing conditions. HD 149757 (zeta Oph) is a fairly shielded environment, whereas the sightline toward HD 147165 (sigma Sco) is exposed to interstellar UV radiation. The DIB at 5797AA has roughly the same strength in both environments, whereas the 5780 DIB is about 4 times stronger in the exposed environments than in the shielded environments. The top right panel illustrates how some DIBs show fairly complex band profiles, reminiscent of rotational contours of large molecules.Figure by Jan Cami.