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We investigate the contribution of clumps and satellites to the galaxy massassembly. 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 thecompact 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 thegalaxy barycenter than the compact ones. Prompted by these observations and bythe comparison with simulations, we suggest that compact blobs are in-situformed clumps, whereas the extended ones are accreting satellites. Clumps andsatellites enclose respectively ~ 20% and ~< 80% of the galaxy stellar mass, ~30% and ~ 20% of its star formation rate. Considering the compact blobs, westatistically estimated that massive clumps (Mstar >~ 10^9 Msun) have lifetimesof ~ 650 Myr, and the less massive ones (10^8 < Mstar < 10^9 Msun) of ~ 145Myr. This supports simulations predicting long-lived clumps (lifetime > 100Myr). Finally, ~< 30% (13%) of our sample galaxies are undergoing single(multiple) merger(s), they have a projected separation ~< 10 kpc, and thetypical 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.

A contribution of star-forming clumps and accreting satellites to the mass assembly of z ~ 2 galaxies