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B.T. Draine, A. Li (Princeton University Observatory)
The silicate/graphite-PAH emission model (Li & Draine 2001) is shown to be applicable to dust in the Small Magellanic Cloud (SMC). The mid-IR emission spectrum of the quiescent molecular cloud SMC B1#1 -- characterized by an unusually high 11.3\mum/7.7\mum band ratio (Reach et al.\ 2000) -- can be explained by PAHs which are mostly neutral, without invoking a higher degree of hydrogenation than for Galactic PAHs. It is also shown that the present dust model is able to reproduce the COBE/DIRBE and IRAS spectral energy distribution from near-IR to far-IR for the SMC B1#1 cloud, as well as for the SMC as a whole. The PAH abundance required in SMC B1#1 is an order of magnitude greater than for the SMC as a whole. The PAH column density required to account for the mid-IR emission spectrum is expected to contribute a 2175Å\ extinction excess of ~0.5 mag through SMC B1#1.
This research was supported by NASA grant NAG5-7030 and NSF grants AST-9619429 and AST-9988126.
References: Li, A., & Draine, B.T. 2001, ApJ, 554, 778. Reach, W.T., Boulanger, F., Contursi, A., & Lequeux, J. 2000, A&A, 361, 895.
The author(s) of this abstract have provided an email address for comments about the abstract: draine@astro.princeton.edu