The star formation history of the Hubble sequence: Spatially resolved colour distributions of intermediate-redshift galaxies in the Hubble Deep Field

We analyse the spatially resolved colours of distant galaxies of known redshift in the Hubble Deep Field, using a new technique based on matching resolved four-band colour data to the predictions of evolutionary synthesis models. Given some simplifying assumptions, we demonstrate how our technique is capable of probing the evolutionary history of high-redshift systems, noting the specific advantage of observing galaxies at an epoch closer to the time of their formation. We quantify the relative age, dispersion in age, on-going star formation rate and star formation history of distinct components. We explicitly test for the presence of dust and quantify its effect on our conclusions. To demonstrate the potential of the method, we study the spirals and ellipticals in the near-complete sample of 32 I814<21.9 mag galaxies with z~0.5 studied by Bouwens, Broadhurst & Silk. The dispersion of the internal colours of a sample of 0.4