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Luminosity Functions and Star Formation Rates at z~6-10: Galaxy Buildup in the Reionization Age

Rychard J. Bouwens·Garth D. Illingworth
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Abstract

HST ACS and NICMOS data are now of sufficient depth and areal coverage to place strong constraints on the formation and evolution of galaxies during the first 1-2 Gyrs of the universe. Of particular interest are galaxies at z~6 since they represent the earliest epoch accessible by current high-efficiency optical instrumentation. To this end, we have constructed a sample of 506 z~6 objects from all the deepest wide-area HST data (UDF, UDF-Parallel, and GOODS fields). They have been used to construct an optimal determination of the rest-frame continuum UV LF at z~6. Our LF extends to over 3 magnitudes below L*, fainter than has been done at z~3. Over the interval z~6 to z~3, we find strong evidence for evolution in the UV LF. Though constraints on the faint-end slope remain modest (and are consistent with no-evolution), the characteristic luminosity appears to have approximately doubled over the interval z~6 to z~3, consistent with hierarchical expectations. Remarkably, this shift to lower luminosities extends to even higher redshifts. Using all deep J+H NICMOS observations (800 orbits in total), we have been able to demonstrate that the bright end of the LF (>0.3L*) is at least 5 times lower at z~10 than at z~4, with a similar deficit being established from our recent detections and first statistical sample of z~7-8 galaxies using our UDF NICMOS data. In these proceedings, we discuss what is known about the UV LF and UV luminosity density at z~6-10 from current data and its evolution relative to z~3. We also describe several exciting prospects for advance in this area over the next year.

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Rychard J. Bouwens, Garth D. Illingworth. 2006-02-24. Luminosity Functions and Star Formation Rates at z~6-10: Galaxy Buildup in the Reionization Age. https://arxiv.org/abs/astro-ph/0510697

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