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Session 45 - Interstellar Medium I.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center

[45.12] K ' -Band Dust Albedo from Observations of Galaxies

A. N. Witt, G. Madsen (U. Toledo), P. Grosbøl (ESO)

A relationship between the dust albedos in the V-band and the K'-band can be obtained by analyzing the relative strengths of dust attenuation in the respective bands in dusty late-type galaxies (Witt et al.\ 1994, ApJ 427, 227). We secured V- and K'-band images of three galaxies which exhibit a highly symmetric light distribution in K' but display exceptionally asymmetric dust attenuation in V: NGC 1546 (Sc(s) III), NGC 1947 (SO_3(0)pec), and NGC 3521 (Sbc(s) II). Differences in V-surface brightness and in V-K' color between diagonally symmetric locations on the galaxy images were analyzed, using galactic radiative transfer models which incorporate both absorption and multiple scattering (Witt, Thronson, amp; Capuano 1992, ApJ 393, 611). Assuming a V-albedo for the dust a_v=0.6, the resulting K'-albedo values for the three galaxies are 0.63, 0.66, and 0.53, respectively. This confirms earlier results, showing the K'-band dust albedo to be well in excess of the value of 0.2 predicted by the MNR model. Thus, the upper limit of the size distribution of grains must extend to at least 1\mum.

Program listing for Tuesday