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B. J. McCall (UIUC), T. Fishman (U. Chicago), S. D. Friedman (STScI), L. M. Hobbs (Yerkes), T. Oka (U. Chicago), B. L. Rachford (Carleton), T. P. Snow (Colorado), P. Sonnentrucker (JHU), J. A. Thorburn (Yerkes), D. E. Welty, D. G. York (U. Chicago)
The diffuse interstellar bands (DIBs) are a ubiquitous set of absorption lines seen in the visible spectra of most reddened stars. The first DIBs were observed by Mary Lea Heger at Lick Observatory in 1919, and to date the molecules responsible for these bands are still unknown. The problem of identifying the carriers of the DIBs is one of the longest-standing puzzles in spectroscopy, and represents a major challenge for laboratory astrophysicists and observers.
From 1999 to 2003, we have conducted an intensive observational survey of the DIBs using a high (R~37500) resolution cross-dispersed echelle spectrograph on the Astrophysical Research Consortium's 3.5-meter telescope at the Apache Point Observatory in New Mexico. We have observed the entire visible region of the spectrum (from 3600--10000 Å) with signal-to-noise ratio exceeding 500, for a sample of 115 stars with color excess E(B-V)>0.1.
We will present our continuing work on the search for sets of DIBs that have the same intensity ratios in all lines of sight. Such a set, if found, would likely represent the electronic spectrum of an individual DIB carrier molecule. We will also discuss the criteria that should be used in evaluating potential DIB carriers, and will illustrate these criteria using the cases of C7- and l-C3H2-.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.