For lensed galaxy SGAS J111020.0 + 645950.8 at redshift z = 2.481 , which is magnified by a factor of 28 \pm 8 , we analyze the morphology of star formation as traced by rest-frame ultraviolet emission , in both the highly-magnified source plane , and in simulations of how this galaxy would appear without lensing magnification .
Were this galaxy not lensed but drawn from an HST deep field , we would conclude that almost all its star formation arises from an exponential disk ( Sérsic index of 1.0 \pm 0.4 ) with an effective radius of r _ { e } = 2.7 \pm 0.3 kpc measured from two-dimensional fitting to F606W using Galfit , and r _ { e } = 1.9 \pm 0.1 kpc measured by fitting a radial profile to F606W elliptical isophotes .
At the normal spatial resolution of the deep fields , there is no sign of clumpy star formation within SGAS J111020.0 + 645950.8 .
However , the enhanced spatial resolution enabled by gravitational lensing tells a very different story : much of the star formation arises in two dozen clumps with sizes of r = 30 –50 pc spread across the 7 kpc length of the galaxy .
The color and spatial distribution of the diffuse component suggests that still smaller clumps are unresolved .
Despite this clumpy , messy morphology , the radial profile is still well-characterized by an exponential profile .
In this lensed galaxy , stars are forming in complexes with sizes well below 100 pc ; such sizes are wholly unexplored by surveys of galaxy evolution at 1 < z < 3 .