GOODS-Herschel:dust attenuation properties of UV selected high redshift galaxies

We study dust attenuation at UV wavelengths at high redshift, where the UV is redshifted to the observed visible. In particular, we search for a UV bump and related implications for dust attenuation determinations. We use data in the CDFS, obtained in intermediate and broad band filters by the MUSYC project, to sample the UV rest-frame of 751 galaxies with 0.95<z<2.2. When available, Herschel/PACS data (GOODS-Herschel project), and Spitzer/MIPS measurements, are used to estimate the dust emission. The SED of each source is fit using the CIGALE code. The amount of dust attenuation and the dust attenuation curve are obtained as outputs of the SED fitting process, together with other parameters linked to the SFH. The global amount of dust attenuation at UV wavelengths is found to increase with stellar mass and to decrease as UV luminosity increases. A UV bump at 2175A is securely detected in 20% of the galaxies, and the mean amplitude of the bump for the sample is similar to that observed in the LMC supershell region. This amplitude is found to be lower in galaxies with very high SSFRs, and 90% of the galaxies exhibiting a secure bump are at z<1.5. The attenuation curve is confirmed to be steeper than that of local starburst galaxies for 20$% of the galaxies. The large dispersion found for these two parameters describing the attenuation law is likely to reflect a wide diversity of attenuation laws among galaxies. The relations between dust attenuation, IR-to-UV flux ratio, and the slope of the UV continuum are derived for the mean attenuation curve found for our sample. Deviations from the average trends are found to correlate with the age of the young stellar population and the shape of the attenuation curve.(abriged)