We analyzed the radial surface brightness profile of the spiral galaxy NGC 7793 using HST /ACS images from the GHOSTS survey and a new HST /WFC3 image across the disk break .
We used the photometry of resolved stars to select distinct populations covering a wide range of stellar ages .
We found breaks in the radial profiles of all stellar populations at 280″ ( \sim 5.1 kpc ) .
Beyond this disk break , the profiles become steeper for younger populations .
This same trend is seen in numerical simulations where the outer disk is formed almost entirely by radial migration .
We also found that the older stars of NGC 7793 extend significantly farther than the underlying H i disk .
They are thus unlikely to have formed entirely at their current radii , unless the gas disk was substantially larger in the past .
These observations thus provide evidence for substantial stellar radial migration in late-type disks .