Monday

We present a new code, 3DCOLORFIT, which was developed to account for ellipticity and colour gradients in weak lensing shear measurements for Euclid. The code does joint fitting of 3D bulge and disc models to galaxy images in multiple bands simultaneously. Here we present results of 7-band fitting (bvizYJH) to HST ACS and WFC3 images of approximately 3000 galaxies out to a redshift of 3 and down to an I band magnitude of 25.5 in the GOODS-South field. We present (1) new distributions of structural parameters such as bulge and disk sizes and bulge light fractions which are much better constrained than single band fits, and their evolution with redshift; (2) colour gradients (defined as the difference between bulge and disc colour) and their evolution with redshift, broadband colour and galaxy morphological type; (3) stellar masses, dust extinction and star formation rates of bulge and disc components (obtained from SED fitting to the component colours) and their evolution with redshift. We use the residual maps (after subtracting the best fit model from the data) to discuss the implications of using these models to characterise galaxies at redshifts between 0.5 and 3. Finally, we discuss how the models can be used to study galaxy structure and stellar populations with future observing facilities such as Euclid and JWST.