  We present new results on the evolution of rest-frame blue/UV sizes and
Sersic indices of H$\alpha$-selected star-forming galaxies over the last 11
Gyrs. We investigate how the perceived evolution can be affected by a range of
biases and systematics such as cosmological dimming and resolution effects. We
use GALFIT and an artificial redshifting technique, which includes the
luminosity evolution of H$\alpha$-selected galaxies, to quantify the change on
the measured structural parameters with redshift. We find typical sizes of 2 to
3 kpc and Sersic indices of n~1.2, close to pure exponential disks all the way
from z=2.23 to z=0.4. At z=0 we find typical sizes of 4-5 kpc. Our results show
that, when using GALFIT, cosmological dimming has a negligible impact on the
derived effective radius for galaxies with <10 kpc, but we find a ~20% bias on
the estimate of the median Sersic indices, rendering galaxies more disk-like.
Star-forming galaxies have grown on average by a factor of 2-3 in the last 11
Gyrs with $r_e\propto(1+z)^{-0.75}$. By exploring the evolution of the stellar
mass-size relation we find evidence for a stronger size evolution of the most
massive star-forming galaxies since z~2, as they grow faster towards z~0 when
compared to the lower stellar mass counterparts. As we are tracing the
rest-frame blue/UV, we are likely witnessing the growth of disks where star
formation is ongoing in galaxies while their profiles remain close to
exponential disks, n<1.5, across the same period.
