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Pseudo–three-dimensional maps of the diffuse interstellar band at 862 nm

Science  15 Aug 2014:
Vol. 345, Issue 6198, pp. 791-795
DOI: 10.1126/science.1253171

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Clues to a mystery with RAVE results

An unknown interloper systematically picks off light from galactic sources, snatching at specific wavelengths ranging from the ultraviolet to the infrared. The cause of what astronomers term diffuse interstellar bands (DIBs) still evades identification. Kos et al. combined nearly 500,000 stellar spectra from the RAVE survey to make a telling map that may clue us in further. This pseudo–three-dimensional map shows the distribution of the carrier that absorbs light at 862 nm, and it closely follows a separate map of interstellar dust, but with a significantly larger scale height in the Galactic plane. Though this is only one DIB of many, this analysis sets a path for the future study of others.

Science, this issue p. 791

Abstract

The diffuse interstellar bands (DIBs) are absorption lines observed in visual and near-infrared spectra of stars. Understanding their origin in the interstellar medium is one of the oldest problems in astronomical spectroscopy, as DIBs have been known since 1922. In a completely new approach to understanding DIBs, we combined information from nearly 500,000 stellar spectra obtained by the massive spectroscopic survey RAVE (Radial Velocity Experiment) to produce the first pseudo–three-dimensional map of the strength of the DIB at 8620 angstroms covering the nearest 3 kiloparsecs from the Sun, and show that it follows our independently constructed spatial distribution of extinction by interstellar dust along the Galactic plane. Despite having a similar distribution in the Galactic plane, the DIB 8620 carrier has a significantly larger vertical scale height than the dust. Even if one DIB may not represent the general DIB population, our observations outline the future direction of DIB research.

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