[59.16] Far Ultraviolet Extinction in Galactic Sight Lines

AAS 205th Meeting, 9-13 January 2005
Session 59 ISM: Dust and Molecules
Poster, Tuesday, January 11, 2005, 9:20am-6:30pm, Exhibit Hall

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[59.16] Far Ultraviolet Extinction in Galactic Sight Lines

U.J. Sofia (Whitman College), M.J. Wolff (SSI), B. Rachford (U. of Colorado), K.D. Gordon (U. of Arizona), G.C. Clayton, S.I.B. Cartledge (LSU), B.T. Draine (Princeton), P.G. Martin (CITA), J.S. Mathis (U. of Wisconsin), T.P. Snow (U. of Colorado), D.C.B. Whittet (Rensselaer)

We present extinction curves that include data down to far ultraviolet wavelengths (FUV; 1000 - 1200 Å) for nine Galactic sight lines. The FUV extinction was measured using data from the Far Ultraviolet Spectroscopic Explorer. The sight lines probe a wide range of dust environments as evidenced by the large spread in their measured ratios of total-to-selective extinction, R_V = 2.43 - 3.81. We find that the Fitzpatrick & Massa relationship appears to be a good predictor of the FUV extinction behavior. That is to say, the Fitzpatrick & Massa function gives very similar fits when applied to data with and without the FUV portion of the extinction curve. We find that predictions of the FUV extinction based upon the Cardelli, Clayton & Mathis (CCM) dependence on R_V give mixed results. For the seven extinction curves well represented by CCM in the infrared through ultraviolet, the FUV extinction is well predicted in three sight lines, over-predicted in two sight lines, and under-predicted in 2 sight lines.

This work was supported by the NASA grants NAG5-108185 and NAG5-9249.

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