A contribution of star-forming clumps and accreting satellites to the
  mass assembly of z ~ 2 galaxies
  We investigate the contribution of clumps and satellites to the galaxy mass
assembly. We analyzed spatially-resolved Hubble Space Telescope observations
(imaging and slitless spectroscopy) of 53 star-forming galaxies at z ~ 1 - 3.
We created continuum and emission line maps and pinpointed residual "blobs"
detected after subtracting the galaxy disk. Those were separated into compact
(unresolved) and extended (resolved) components. Extended components have sizes
~ 2 kpc and comparable stellar mass and age as the galaxy disks, whereas the
compact components are 1.5 dex less massive and 0.4 dex younger than the disks.
Furthermore the extended blobs are typically found at larger distances from the
galaxy barycenter than the compact ones. Prompted by these observations and by
the comparison with simulations, we suggest that compact blobs are in-situ
formed clumps, whereas the extended ones are accreting satellites. Clumps and
satellites enclose respectively ~ 20% and ~< 80% of the galaxy stellar mass, ~
30% and ~ 20% of its star formation rate. Considering the compact blobs, we
statistically estimated that massive clumps (Mstar >~ 10^9 Msun) have lifetimes
of ~ 650 Myr, and the less massive ones (10^8 < Mstar < 10^9 Msun) of ~ 145
Myr. This supports simulations predicting long-lived clumps (lifetime > 100
Myr). Finally, ~< 30% (13%) of our sample galaxies are undergoing single
(multiple) merger(s), they have a projected separation ~< 10 kpc, and the
typical mass ratio of our satellites is 1:5 (but ranges between 1:10 and 1:1),
in agreement with literature results for close pair galaxies.
