AAS 207th Meeting, 8-12 January 2006
Session 149 AGN: Host Galaxies and Clustering
Oral, Wednesday, 10:00-11:30am, January 11, 2006, Salon 1

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[149.01] Reddening and Ultraviolet Extinction Curves from Hubble Space Telescope Spectra

C. M. Gaskell (U. Nebraska), A. J. Benker (U.C. Irvine)

We present intrinsic extinction curves for 14 AGNs. The AGNs have reddenings, E(B-V), of up to 0.36 mag. The majority (13 out of 14) of the extinction curves are not steep in the UV. Of the seven best determined extinction curves, five have extinction curves that are as flat as the standard Galactic curve, and flatter in the far UV, but without the \lambda2175 feature. One AGN has a steep SMC-like extinction curve, and another has an LMC-like extinction curve, including a probable \lambda2175 bump. The remaining seven, lower-quality, extinction curves have overall shapes that are consistent with an LMC-like shape or a flatter shape. Two have possible \lambda2175 features, and one might be identical to the Galactic curve. The flatter curves that predominate in our best determined extinction curves are not as flat as the Gaskell et al. (2004) extinction curve for radio-loud AGNs. This suggests that the previous radio-loud extinction curve might be slightly too flat in the range 4 < 1/\lambda < 6.5 \mum-1 because of luminosity-dependent reddening biases in the composite spectra, but further investigation is needed. Observed variations in the continuum properties of the AGNs are inconsistent with intrinsic object-to-object variations because observed differences are least in the far UV where changes in the accretion disk spectrum should be greatest. We suggest that the steepening of AGN spectra around Lyman \alpha is the result of a small amount of SMC-like dust (E(B-V) ~0.03). We find the largest object-to-object differences in spectral shape to be in the Fe II emission of the ``small blue bump''.

This research has been supported by the University of Nebraska Undergraduate Creativity and Research Experience (UCARE) program, by the National Science Foundation through grant AST 03-07912, and by the Space Telescope Science Institute through grant AR-09926.01.

If you would like more information about this abstract, please follow the link to http://www.physics.unl.edu/directory/gaskell/preprints/preprints.html. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: mgaskell1@unl.edu

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