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Detection of Diffuse Interstellar Bands in the z=0.5 Damped Lyman alpha system towards AO 0235+164

Brian A. York·Sara L. Ellison·Brandon Lawton·Christopher W. Churchill·Theodore P. Snow·Rachel A. Johnson·Sean G. Ryan
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Abstract

We report the first detection of the 5705 and 5780 A Diffuse Interstellar Bands (DIBs) in a moderate redshift Damped Lyman alpha (DLA) system. We measure a rest frame equivalent width of 63.2 +- 8.7 mA for the 5705 and 216+-9 mA for the 5780 A feature in the z_abs 0.524 DLA towards AO 0235+164 and derive limits for the equivalent widths of the bands at 5797, 6284, and 6613 A. The equivalent width of the 5780 band is lower than would be expected based on the Galactic correlation of DIB strength with N(HI), but is in good agreement with the correlation with E(B-V). The relative strengths of the 5780 and 6284 A DIBs are inconsistent with all Galactic and extragalactic sightlines, except one Small Magellanic Cloud wing sightline towards Sk 143. However, the relative strengths of the 5705 and 5780 A DIBs are consistent with the Galactic relation, indicating that the relative strengths of these bands may be less sensitive to environment or that they may be associated with a similar carrier. The detection of DIBs at z~0.5 demonstrates that the organic compounds usually assumed to be the band carriers were already present in the universe some five gigayears ago.

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Brian A. York, Sara L. Ellison, Brandon Lawton, Christopher W. Churchill, Theodore P. Snow, Rachel A. Johnson, Sean G. Ryan. 2006-05-18. Detection of Diffuse Interstellar Bands in the z=0.5 Damped Lyman alpha system towards AO 0235+164. https://doi.org/10.1086/505907

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