Poster abstract details

Binary stars and the UVX in early type galaxies
Fabiola Hernández-Pérez and Gustavo Bruzual


We assemble a sample of 3417 Early Type Galaxies observed both in the optical (\textit{SDSS}-DR8) and the UV (\textit{GALEX}-GR6). The galaxies in our sample can be classified according to their position in the colour-colour diagram as UV weak, UV strong and recent star forming galaxies. Analyzing this sample using the Hern\'andez-P\'erez \& Bruzual 2013 models for various choices of basic model binary parameters we conclude that: \textit{(a)} The UV$r$ colours of UV weak and UV strong galaxies are reproduced by the models as long as the fraction of binary stars is at least 15\%. \textit{(b)} Higher metallicity models ($Z = 0.02$ and $Z = 0.03$) reproduce the colours of UV weak and UV strong galaxies better than lower $Z$ models. The $Z = 0.03$ model is slightly bluer than the $Z = 0.02$ model in the UV strong region, indicating a weak relationship between UVX and $Z$. \textit{(c)} The strength of UVX increases with age in the model population.