The Evolution of Galaxy Dust Properties for 1 < z < 2 . 5

Fundamental properties of the extinction curve, like the slope in the rest-frame UV and the presence/absence of a broad absorption excess centred at 2175 Å (the UV bump), are investigated for a sample of 108 massive, starforming galaxies at 1 < z < 2.5, selected from the FDF Spectroscopic Survey, the K20 survey, and the GDDS. These characteristics are constrained from a parametric description of the UV spectral energy distribution of a galaxy. It turns out that the sample galaxies host dust producing extinction curves with properties in between those of the Small and Large Magellanic Clouds (SMC and LMC, respectively). LMC-like extinction curves, which exhibit a UV bump, are mainly found among highly-reddened, UV-ultraluminous galaxies at z ∼ 2.4 and highly-reddened, near-IR-bright, star-forming galaxies at z ∼ 1.2. We discuss star-formation rates, total stellar masses, the morphology, and the chemical properties of our sample galaxies with respect to possible explanations for the different extinction curves.