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
  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.
