Dust attenuation in the restframe ultraviolet : constraints from star – forming galaxies at z ∼ 1

A novel technique is employed for estimating attenuation curves in galaxies where only photometry and spectroscopic redshifts are available. This technique provides a powerful measure of particular extinction features such as the UV bump at 2175Å, which has been observed in environments ranging from the Milky Way to high–redshift star–forming galaxies. Knowledge of the typical strength of the UV bump as a function of environment and redshift is crucial for converting restframe UV flux into star formation rates. The UV bump will impart a unique signature as it moves through various filters due to redshifting; its presence can therefore be disentangled from other stellar population effects. The utility of this technique is demonstrated with a large sample of galaxies drawn from the DEEP2 Galaxy Redshift Survey. The observed B−R color of star–forming galaxies at 0.6 < z < 1.4 disfavors the presence of a UV bump as strong as observed in the Milky Way, and instead favors restframe UV (1800Å< λ < 3000Å ) attenuation curves similar to the Milky Way without a UV bump or a power–law with index δ = −0.7. Stronger constraints on the strength of the UV bump in galaxies can be achieved if independent constraints on the V -band optical depth are available.