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Date and Time of the Query: 2019-04-24 T08:19:47 PDT
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For refcode 2012MNRAS.427..688L:
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Copyright by Royal Astronomical Society. 2012MNRAS.427..688L Hubble Space Telescope Halpha imaging of star-forming galaxies at z ~= 1-1.5: evolution in the size and luminosity of giant H II regions Livermore, R. C.; Jones, T.; Richard, J.; Bower, R. G.; Ellis, R. S.; Swinbank, A. M.; Rigby, J. R.; Smail, Ian; Arribas, S.; Rodriguez Zaurin, J.; Colina, L.; Ebeling, H.; Crain, R. A. Abstract. We present Hubble Space Telescope/Wide Field Camera 3 narrow-band imaging of the Halpha emission in a sample of eight gravitationally lensed galaxies at z = 1-1.5. The magnification caused by the foreground clusters enables us to obtain a median source plane spatial resolution of 360 pc, as well as providing magnifications in flux ranging from ~10x to ~50x. This enables us to identify resolved star-forming H II regions at this epoch and therefore study their Halpha luminosity distributions for comparisons with equivalent samples at z ~ 2 and in the local Universe. We find evolution in the both luminosity and surface brightness of H II regions with redshift. The distribution of clump properties can be quantified with an H II region luminosity function, which can be fit by a power law with an exponential break at some cut-off, and we find that the cut-off evolves with redshift. We therefore conclude that 'clumpy' galaxies are seen at high redshift because of the evolution of the cut-off mass; the galaxies themselves follow similar scaling relations to those at z = 0, but their H II regions are larger and brighter and thus appear as clumps which dominate the morphology of the galaxy. A simple theoretical argument based on gas collapsing on scales of the Jeans mass in a marginally unstable disc shows that the clumpy morphologies of high-z galaxies are driven by the competing effects of higher gas fractions causing perturbations on larger scales, partially compensated by higher epicyclic frequencies which stabilize the disc. Key words: gravitational lensing: strong, galaxies: high-redshift, galaxies: star formation
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