tokens: 2014 ; Roman-Duval et al. 2014 ). 8 For each of the tested models, Gordon et al. ( 2014 ) provide three different realizations of the best-fitting parameters. Of these, we adopt the best-fitting parameters corresponding to the expectation value of the full likelihood function for each parameter (see section 4.3 of Gordon et al. 2014 for details). The most important parameter of the BEMBB model, in terms of investigating the dust content across the SMC, is the dust surface density Σ d . To transform the dust surface densities to E ( B − V ) values for a direct comparison with our reddening map based on the background galaxies, we follow the formalism described by Whittet ( 2003 ). The relation between the total extinction at a given wavelength, λ, and the optical depth of extinction caused by the dust, τ d , is given by We can express this total extinction in terms of the extinction efficiency factor, Q ext : where N d is the column density of the dust and a is the radius of the dust grains (see section 3.1.1 of Whittet 2003 for a full derivation). The dust surface density Σ d is related to N d via where ρ d is the density of the dust grains. We can calculate the V -band extinction using the V -band extinction efficiency factor Q V , such that We adopt the following values for the remainder of the variables in equation ( 4 ): Q V = 1.4 (Chlewicki 1985 ) and, assuming ‘classical’ dust grains, a = 0.1 μm and ρ d = 3 g cm −3 (Mann Kimura 2000 ; Whittet 2003 ; Kohout et al. 2014 ). Finally, we convert A V into E ( B − V ) following the standard A V = 3.1 × E ( B − V ) (Cardelli et al. 1989 ). Note that the values of Σ d represent only the internal dust content of the SMC. Prior to fitting the HERITAGE data, Gordon et al. ( 2014 ) use the integrated MW H i velocity maps in the directions of the SMC (Stanimirović et al. 1999 ; Muller et al. 2003 ) to subtract the structured emission due to the MW. 4.2 Quantitative comparisons Fig. 6 presents the comparison between our reddening map based on galaxies with low levels of intrinsic reddening and the various reddening maps of the SMC discussed in Section 4.1 . To facilitate the comparison, we have resampled the literature maps to a 20 × 20 arcmin 2 resolution by simply taking the median reddening value of all stars/cells that fall within a given bin. This resampling of the literature maps will undoubtedly result in the loss of small-scale (less than 20 arcmin in size) features in these maps. Any large-scale morphological features, however, such as pervasive enhancements of dust along the main body of the SMC, should be preserved and visible in the maps presented in Fig. 6 . Figure 6. 20 × 20 arcmin 2 resolution reddening maps covering the SMC. Each panel refers to a different literature source. The contours in all panels represent the IRAS 100 μm dust emission. The dashed line in the lower right panel represents the footprint of the HERITAGE observations. Of the eight literature maps shown, three
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