Revisiting the Lyman Continuum Escape Crisis: Predictions for z > 6 from
  Local Galaxies
  The intrinsic escape fraction of ionizing Lyman continuum photons ($f_{esc}$)
is crucial to understand whether galaxies are capable of reionizing the neutral
hydrogen in the early universe at z>6. Unfortunately, it is not possible to
access $f_{esc}$ at z>4 with direct observations and the handful of
measurements from low redshift galaxies consistently find $f_{esc}$ < 10%,
while at least $f_{esc}$ ~ 10% is necessary for galaxies dominate reionization.
Here, we present the first empirical prediction of $f_{esc}$ at z>6 by
combining the (sparsely populated) relation between [OIII]/[OII] and $f_{esc}$
with the redshift evolution of [OIII]/[OII] as predicted from local high-z
analogs selected by their H$\alpha$ equivalent-width. We find $f_{esc}$ =
$5.7_{-3.3}^{+8.3}$% at z=6 and $f_{esc}$ = $10.4_{-6.3}^{+15.5}$% at z=9 for
galaxies with log(M/M$_{sun}$) ~ 9.0 (errors given as 1$\sigma$). However,
there is a negative correlation with stellar mass and we find up to 50% larger
$f_{esc}$ per 0.5 dex decrease in stellar mass. The population averaged escape
fraction increases according to $f_{esc}$ = $f_{esc,0} ((1+z)/3)^a$, with
$f_{esc,0} = 2.3 \pm 0.05$% and $a=1.17 \pm 0.02$ at z > 2 for log(M/M$_{sun}$)
~ 9.0. With our empirical prediction of $f_{esc}$ (thus fixing an important
previously unknown variable) and further reasonable assumption on clumping
factor and the production efficiency of Lyman continuum photons, we conclude
that the average population of galaxies is just capable to reionize the
universe by z ~ 6.
