AAS 205th Meeting, 9-13 January 2005
Session 145 Intergalactic Media
Poster, Thursday, January 13, 2005, 9:20am-4:00pm, Exhibit Hall

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[145.07] The Search for Extragalactic Diffuse Interstellar Bands via QSO Absorption Line Systems

B. Lawton, C. W. Churchill (New Mexico State University)

How common are the building blocks of life in the Universe? We hope to further our knowledge in this field by searching QSO absorption line systems for organic molecules in extragalactic sources. Within the Milky Way, complex organic molecules are thought to be the cause of ~300 absorption features known as the diffuse interstellar bands (DIBs) found mostly within the visible part of the electromagnetic spectrum. Although abundant in the Milky Way, DIBs have only been found in a few extragalactic sources and only in one source via QSO absorption lines. Other researchers in this field have shown tight correlations between a specific DIB equivalent width and reddening as well as DIB equivalent width and neutral hydrogen column density. However, DIB strengths do not correlate with molecular hydrogen. From these observations many conclusions have been ascertained as to the environment of DIBs, as will be discussed within the poster. Due to these results we show why QSO absorption line systems containing very high column densities of neutral hydrogen are the appropriate mechanisms for searching extragalactic sources of DIBs. In particular, we have searched for DIBs using high resolution Keck data in QSO 0827+243 which contains an absorber with log column density of neutral hydrogen equal to 2.0. We have detected no DIBs in this system; however, we have developed a method of estimating the normalized absorption strengths of DIB lines we would expect to see given a neutral hydrogen column density of our target absorber. In this particular case, we would not expect to have found DIBs in 0827+243. We also present future work which includes systematically searching for DIBs in low redshift QSO absorption line systems. This work is being funded by NASA GSRP through the Office of Space Science.

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