Detection of diffuse interstellar bands in the z=0.5 damped Ly alpha system toward AO 0235+164

Journal article

We report the first detection of the 5705 and 5780 A diffuse interstellar bands (DIBs) in a moderate-redshift damped Lyα (DLA) system. We measure a rest-frame equivalent width of 63.2 ± 8.7 mA for the 5705 Å feature and 216 ±9 mÅ for the 5780 A feature in the zabs = 0.524 DLA toward 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 Å band is lower than would be expected based on the Galactic correlation of DIB strength with N(H I) but is in good agreement with the correlation with E(B-V). The relative strengths of the 5780 and 6284 Å DIBs are inconsistent with all Galactic and extragalactic sight lines, except one Small Magellanic Cloud wing sight line toward Sk 143. However, the relative strengths of the 5705 and 5780 Å 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 5 Gyr ago. © 2006. The American Astronomical Society. All rights reserved.

Authors: York, B; Ellison, S; Lawton, B; Churchill, C; Snow, T

• Publication status: Published
• Publisher: Institute of Physics Publishing
• Journal: ASTROPHYSICAL JOURNAL
• Volume: 647
• Issue: 1
• Pages: L29-L32
• Publication date: 2006-08-10
• DOI: 10.1086/505907
• EISSN: 1538-4357
• ISSN: 0004-637X
• Language: English
• Keywords: Quasars: absorption lines; ISM: lines and bands; ISM: molecules