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Paper: Carbon Abundances in Interstellar Gas and Dust
Volume: 414, Cosmic Dust—Near and Far
Page: 236
Authors: Sofia, U. J.; Parvathi, V. S.
Abstract: Carbon is arguably the most important element in dust, yet its abundance in grains is poorly understood due to a paucity of data. The primary source of interstellar neutral-cloud carbon abundances has been the weak C II] 2325 Å feature, a measurement of which requires high resolution and signal-to-noise ultraviolet spectra. The stringent data requirements have yielded only 13 abundance measurements in neutral interstellar regions. Since merely seven of these sight lines have measured extinction curves, relating the carbon abundance in grains to specific extinction characteristics is nearly impossible. For that reason we have been testing the possibility of obtaining interstellar C II abundances from the strong 1334 Å transition, of which there are more observations. Our preliminary results show that careful analysis of this line is able yield reliable interstellar gas-phase carbon abundances. Our tests have used the translucent-sight-line sample of Sofia et al. (2004). For these six sight lines, the strong-line method consistently shows a lower gas-phase C abundance than the measurements from the weak lines. This implies that more carbon resides in dust than was previously thought, which may solve the carbon crisis. We are extending our sample to include all of the STIS archived data for sight lines with measured interstellar hydrogen abundances.
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