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U. P. Vijh, A. N. Witt (University of Toledo), K. D. Gordon (University of Arizona)
In order to determine the star formation history of the universe from deep surveys at UV/optical rest frame wavelengths, one must have a reliable estimate of the attenuation factor for galaxies at high redshifts. That star formation is heavily enshrouded in dust is no longer in doubt. The exact nature, geometry and the amount of this dust/attenuation needs to be known out to high redshifts.
We present an analysis of UV attenuation of a large (N=906) sample of Lyman Break Galaxies (LBGs) (data provided by Charles C. Steidel, Caltech) by internal dust. Using spectral energy distributions (SEDs) from the PEGASE stellar evolutionary synthesis model we apply dust corrections to the G~-~R colours using the Witt & Gordon (2000) dust attenuation models, to arrive at the UV attenuation factors.
We show that the dust in the LBG sample exhibits SMC-like characteristics rather than MW type, and that the dust geometry is best represented by a clumpy shell configuration. The dust attenuation in individual LBGs is found to be proportional to their rest frame UV luminosities, i.e. their current star formation rate. We find that the average luminosity-weighted dust attenuation factor at 1600 Å~is in the range 10-40 which agrees with the upper limit set by the FIR background. We also find that most of the star formation at 2 < z < 4 occurs in galaxies with luminosity ~1011-1012L\odot, equivalent to of the present day Luminous Infra-Red Galaxies and the Ultra Luminous Infra-Red Galaxies.
This work has been supported by NASA grants NAG5-9376 and NAG5-9202, which we acknowledge with gratitude.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.