On the stellar masses of giant clumps in distant star-forming galaxies
  We analyse stellar masses of clumps drawn from a compilation of star-forming
galaxies at 1.1<z<3.6. Comparing clumps selected in different ways, and in
lensed or blank field galaxies, we examine the effects of spatial resolution
and sensitivity on the inferred stellar masses. Large differences are found,
with median stellar masses ranging from ~10^9 Msun for clumps in the
often-referenced field galaxies to ~10^7 Msun for fainter clumps selected in
deep-field or lensed galaxies. We argue that the clump masses, observed in
non-lensed galaxies with a limited spatial resolution of ~1 kpc, are
artificially increased due to the clustering of clumps of smaller mass.
Furthermore, we show that the sensitivity threshold used for the clump
selection affects the inferred masses even more strongly than resolution,
biasing clumps at the low mass end. Both improved spatial resolution and
sensitivity appear to shift the clump stellar mass distribution to lower
masses, qualitatively in agreement with clump masses found in recent
high-resolution simulations of disk fragmentation. We discuss the nature of the
most massive clumps, and we conclude that it is currently not possible to
properly establish a meaningful clump stellar mass distribution from
observations and to infer the existence and value of a characteristic clump
mass scale.
