AAS Meeting #193 - Austin, Texas, January 1999
Session 65. Interstellar Dust and Gas
Display, Friday, January 8, 1999, 9:20am-6:30pm, Exhibit Hall 1

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[65.02] Interpretation of Extragalactic Extinction Measurements Using the Maximum Entropy Method

M.J. Wolff (Space Science Institute), G.C. Clayton, K.D. Gordon, K.A. Misselt (Astronomy/LSU)

We present size distributions of interstellar dust grains derived from several sightlines in three Local Group galaxies: Small and Large Magellanic Clouds, and M31. Employing the Maximum Entropy Method algorithm, as developed by Kim et al. (1994a,b; 1995), we fit interstellar extinction measurements which span the wavelength range 0.125-3\micron. In order to facilitate comparison, our sample includes several Galactic sightlines whose extinction curves share some similarities with the extragalactic targets. Our work has greatly benefited from the recent reanalysis of IUE observations of the Magellanic Clouds (Gordon & Clayton 1998; Misselt et al. 1998). The grain models employed for this presentation are the simplistic homogeneous spheres models (i.e., Mathis, Rumpl, & Nordsieck 1977) with two (graphite, silicate) or three (graphite, silicate, amorphous carbon) components. Though such usage is only a first step, the results do provide interesting insight into the use of grain size as a diagnostic of extragalactic environment.

\noindent References:\\ Gordon, K.D. & Clayton, G.C. 1998, ApJ, in press\\ Kim, S.-H. & Martin, P.G. 1994a, ApJ, 431, 783\\ Kim, S.-H. & Martin, P.G. 1995, ApJ, 442, 172\\ Kim, S.-H., Martin, P.G., Hendry, P.D. 1994b, ApJ, 422, 164\\ Mathis, J.S., Rumpl, W., & Nordsieck, K.H. 1977, ApJ, 217, 425\\ Misselt, K.A., Clayton, G.C., & Gordon, K.D. 1998, ApJ, submitted

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