Multiply lensed star forming clumps in the A521-sys1 galaxy at redshift 1

ABSTRACT We study the population of star-forming clumps in A521-sys1, a $z=1.04$ system gravitationally lensed by foreground ($z=0.25$) cluster Abell 0521. The galaxy presents one complete counter-image with mean magnification $\rm \mu \sim 4$ and wide arc containing two partial images A521-sys1 magnifications reaching $\mu > 20$, allowing investigations down to scales ${\rm R}_{\rm eff} < 50$ pc. identify 18 unique total 45 multiple images. Intrinsic sizes UV magnitudes reveal elevated surface brightnesses comparable similar systems at redshifts $z\gtrsim 1.0$. Such account for ${\sim}40\,\rm{per\ cent}$ luminosity implying significant fraction recent star-formation activity is taking place there. Clump masses range from 106 $10^9\,{\rm M}_\odot$ tens hundreds parsec resulting mass densities 10 $10^3\,{\rm M}_\odot\,{\rm pc}^{-2}$ median ${\sim}10^2\,{\rm pc}^{-2}$. These properties suggest that we detect star formation across scale aggregates giant complexes. find ages less than 100 Myr consistent being observed close their natal region. lack galactocentric trends mass, density, or age old migrated can be explained either dissolution after few ?100 stellar evolution making them fall below detectability limits our data.