Truncation of stellar disks in galaxies at z~1

We report here the first evidence for stellar disk truncation at high redshift, based on surface photometry of a sample of 16 high redshift (0.6 < z < 1.0) disk galaxies from the GOODS HST/ACS data. The radial profiles are best fit by a double exponential profile. This result agrees with the profile of disks in local galaxies. The cosmological surface brightness dimming at this redshift range only allows us to detect galaxies with spatially early'' truncation, R_br/h_in <= 3.5. Six galaxies show the radial double exponential structure, with an average value of R_br/h_in ~ 1.8. Such early’’ truncated galaxies are missing in local samples so far. This result opens the ground for observing directly disk evolution through the study of the truncation radius as a function of redshift.