Resolved spectroscopy of gravitationally lensed galaxies: global dynamics and star-forming clumps on ∼100 pc scales at 1 < z < 4

We present adaptive optics-assisted integral field spectroscopy around the H alpha or H beta lines of 12 gravitationally lensed galaxies obtained with VLT/SINFONI, Keck/OSIRIS and Gemini/NIFS. We combine these data with previous observations and investigate the dynamics and star formation properties of 17 lensed galaxies at 1 < z< 4. Thanks to gravitational magnification of 1.4-90 times by foreground clusters, effective spatial resolutions of 40-700 pc are achieved. The magnification also allows us to probe lower star formation rates (SFRs) and stellar masses than unlensed samples; our target galaxies feature dust-corrected SFRs derived from H alpha or H beta emission of similar to 0.8-40M(circle dot) yr(-1), and stellar masses M-* similar to 4 x 10(8)-6 x 10(10) M-circle dot. All of the galaxies show velocity gradients, with 59 per cent consistent with being rotating discs and a likely merger fraction of 29 per cent, with the remaining 12 per cent classed as 'undetermined'. We extract 50 star-forming clumps with sizes in the range 60 pc-1 kpc from the H alpha (or H beta) maps, and find that their surface brightnesses, Sigma(clump) and their characteristic luminosities, L-0, evolve to higher luminosities with redshift. We show that this evolution can be described by fragmentation on larger scales in gas-rich discs, and is likely to be driven by evolving gas fractions.