The dust in Lyman break galaxies

We present our analysis of UV attenuation by internal dust of a large sample (N = 906 galaxies) of Lyman break galaxies (LBGs). Using spectral energy distributions (SEDs) from the PEGASE galaxy spectral evolution model, we apply dust attenuation corrections to the G-R colors, using the Witt & Gordon models for radiative transfer in dusty galactic environments to arrive at the UV attenuation factors. We show that the dust in the LBGs exhibits SMC-like rather than Milky Way-like characteristics and that the dust geometry in these systems is most likely to be represented by a clumpy shell configuration. We show that the attenuation factor exhibits a pronounced dependence on the luminosity of the LBG, a(1600) proportional to (L/L-circle dot)(alpha), where 0.5 less than or equal to alpha less than or equal to 1.5. The exponent alpha depends on the initial parameters of the stellar population chosen to model the galaxies and the dust properties. We find that the luminosity-weighted average attenuation factor is likely to be in the range from 5.7 to 18.5, which is consistent with the upper limits to the star formation rate at 2 < z < 4 set by the far-infrared background. This implies that the current UV/optical surveys do detect the bulk of the star formation during the epoch 2 < z < 4 but require substantial correction for internal dust attenuation.