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| Paper: |
Galaxy Buildup in the First 2 Gyr: New Constraints on the Evolution of the UV LF from z∼8 to z∼4 |
| Volume: |
399, Panoramic Views of Galaxy Formation and Evolution |
| Page: |
28 |
| Authors: |
Bouwens, R.J.; Illingworth, G.D. |
| Abstract: |
Very large samples of galaxies have been assembled at z∼4, 5 and 6 from all the deep HST ACS imaging data ever taken (a remarkable 4671, 1416, and 627 sources, respectively), allowing us to derive LFs that reach 4-5 mag fainter than L*. A striking result is that the faint-end slope is constant and very steep (∼ −1.7). Within the errors, the number density φ* is roughly constant, but the characteristic luminosity M* brightens significantly over this period by 0.7 mag. The observed increase in the characteristic luminosity is almost identical to the increase expected for the halo mass function suggesting that the observed evolution is likely due to the hierarchical coalescence and merging of galaxies into larger systems. In order to obtain similar constraints on the UV LF at z≥7, we have taken advantage of all available deep HST ACS NICMOS data to significantly expand the size of our samples of star-forming galaxies at z≥7. Our current samples include ≥9 strong z∼7 candidates (more than double the number from last year), allowing us to obtain significant constraints on the characteristic luminosity M* at z∼7. We find that the brightening observed in M* from z∼6 to z∼4 is also found at even early times, to z∼7. Improved constraints have also been set on the volume density of star-forming galaxies at z∼10, and there is good evidence that the UV LF evolves from z∼10 to z∼7. Our results demonstrate that the hierarchical build-up seen from z∼6 to z∼4 is now found to occur over ∼1 Gyr from z∼7-10 within the reionization epoch to z∼4. |
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