A Census of Star-Forming Galaxies in the z~9-10 Universe based on HST+Spitzer Observations Over 19 CLASH clusters: Three Candidate z~9-10 Galaxies and Improved Constraints on the Star Formation Rate Density at z~9

• Main Authors: Bouwens, R, Bradley, L, Zitrin, A, Coe, D, Franx, M, Zheng, W, Smit, R, Host, O, Postman, M, Moustakas, L, Labbe, I, Carrasco, M, Molino, A, Donahue, M, Kelson, D. D, Meneghetti, M, Benitez, N, Lemze, D, Umetsu, K, Broadhurst, T, Moustakas, J, Rosati, P, Bartelmann, M, Ford, H, Graves, G, Grillo, C, Infante, L, Jiminez-Teja, Y, Jouvel, S, Lahav, O, Maoz, D, Medezinski, E, Melchior, P, Merten, J, Nonino, M, Ogaz, S, Seitz, S
• Format: Journal Article
• Language: English
• Published: 03-09-2014
• Subjects: Physics - Cosmology and Nongalactic Astrophysics
• DOI: 10.48550/arxiv.1211.2230

We utilise a two-color Lyman-Break selection criterion to search for z~9-10
galaxies over the first 19 clusters in the CLASH program. A systematic search
yields three z~9-10 candidates. While we have already reported the most robust
of these candidates, MACS1149-JD, two additional z~9 candidates are also found
and have H_{160}-band magnitudes of ~26.2-26.9. A careful assessment of various
sources of contamination suggests <~1 contaminants for our z~9-10 selection. To
determine the implications of these search results for the LF and SFR density
at z~9, we introduce a new differential approach to deriving these quantities
in lensing fields. Our procedure is to derive the evolution by comparing the
number of z~9-10 galaxy candidates found in CLASH with the number of galaxies
in a slightly lower redshift sample (after correcting for the differences in
selection volumes), here taken to be z~8. This procedure takes advantage of the
fact that the relative volumes available for the z~8 and z~9-10 selections
behind lensing clusters are not greatly dependent on the details of the lensing
models. We find that the normalization of the UV LF at z~9 is just
0.28_{-0.20}^{+0.39}\times that at z~8, ~1.4_{-0.8}^{+3.0}x lower than
extrapolating z~4-8 LF results. While consistent with the evolution in the UV
LF seen at z~4-8, these results marginally favor a more rapid evolution at z>8.
Compared to similar evolutionary findings from the HUDF, our result is less
insensitive to large-scale structure uncertainties, given our many independent
sightlines on the high-redshift universe.