Jason Jaacks, Jun-Hwan Choi, Kentaro Nagamine, Robert Thompson, Saju Varghese
We present the results of a numerical study comparing photometric and
physical properties of simulated $z=6-9$ galaxies to the observations taken by
the WFC3 instrument aboard the Hubble Space Telescope. Using cosmological
hydrodynamical simulations we find good agreement with observations in
color-color space at all studied redshifts. We also find good agreement between
observations and our Schechter luminosity function fit in the observable range,
$\Muv\leq -18$, provided that a moderate dust extinction effect exists for
massive galaxies. However beyond what currently can be observed, simulations
predict a very large number of low-mass galaxies and evolving steep faint-end
slopes from $\alpha_L = -2.15$ at $z=6$ to $\alpha_L = -2.64$ at $z=9$, with a
dependence of $|\alpha_L| \propto (1+z)^{0.59}$. During the same epoch, the
normalization $\phi^{*}$ increases and the characteristic magnitude $\Muv^*$
becomes moderately brighter with decreasing redshift. We find similar trends
for galaxy stellar mass function with evolving low-mass end slope from
$\alpha_M = - 2.26$ at $z=6$ to $\alpha_M = -2.87$ at $z=9$, with a dependence
of $|\alpha_M| \propto (1+z)^{0.65}$. Together with our recent result on the
high escape fraction of ionizing photons for low-mass galaxies, our results
suggest that the low-mass galaxies are important contributor of ionizing
photons for the reionisation of the Universe at $z\ge 6$.
View original:
http://arxiv.org/abs/1104.2345
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