# THE BRIGHT END OF THE z similar to 9 AND z similar to 10 UV LUMINOSITY FUNCTIONS USING ALL FIVE CANDELS FIELDS

Bouwens, RJ, Oesch, PA, Labbe, I, Illingworth, GD, Fazio, GG, Coe, D, Holwerda, B, Smit, R, Stefanon, M, van Dokkum, PG, Trenti, M, Ashby, MLN, Huang, J-S, Spitler, L, Straatman, C, Bradley, L and Magee, D (2016) THE BRIGHT END OF THE z similar to 9 AND z similar to 10 UV LUMINOSITY FUNCTIONS USING ALL FIVE CANDELS FIELDS. Astrophysical Journal, 830 (2). ISSN 0004-637X

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1506.01035v4.pdf - Accepted Version

The deep, wide-area (~800–900 arcmin2) near-infrared/WFC3/IR + Spitzer/IRAC observations over the CANDELS fields have been a remarkable resource for constraining the bright end of high-redshift UV luminosity functions. However, the lack of Hubble Space Telescope (HST) 1.05 μm observations over the CANDELS fields has made it difficult to identify z ~ 9–10 sources robustly, since such data are needed to confirm the presence of an abrupt Lyman break at 1.2 μm. Here, we report on the successful identification of many such z ~ 9–10 sources from a new HST program (z9-CANDELS) that targets the highest-probability z ~ 9–10 galaxy candidates with observations at 1.05 μm, to search for a robust Lyman-break at 1.2 μm. The potential z ~ 9–10 candidates were preselected from the full HST, Spitzer/IRAC S-CANDELS observations, and the deepest-available ground-based optical+near-infrared observations (CFHTLS-DEEP+HUGS+UltraVISTA+ZFOURGE). We identified 15 credible z ~ 9–10 galaxies over the CANDELS fields. Nine of these galaxies lie at z ~ 9 and five are new identifications. Our targeted follow-up strategy has proven to be very efficient in making use of scarce HST time to secure a reliable sample of z ~ 9–10 galaxies. Through extensive simulations, we replicate the selection process for our sample (both the preselection and follow-up) and use it to improve current estimates for the volume density of bright z ~ 9 and z ~ 10 galaxies. The volume densities we find are 5${}_{-2}^{+3}\times$ and ${8}_{-3}^{+9}\times$ lower, respectively, than those found at z ~ 8. When compared with the best-fit evolution (i.e., $d\,{\mathrm{log}}_{10}\,{\rho }_{\mathrm{UV}}/{dz}=-0.29\pm 0.02$) in the UV luminosity densities from z ~ 8 to z ~ 4 integrated to $0.3{L}_{z=3}^{* }$ (−20 mag), these luminosity densities are ${2.6}_{-0.9}^{+1.5}\times$ and ${2.2}_{-1.1}^{+2.0}\times$ lower, respectively, than the extrapolated trends. Our new results are broadly consistent with the "accelerated evolution" scenario at z > 8, consistent with that seen in many models.