Title: A High Space Density of Luminous Lyman Alpha Emitters at z~6.5,
Abstract: We present the results of a systematic search for Lyman-alpha emitters (LAEs)
at $6 \lesssim z \lesssim 7.6$ using the HST WFC3 Infrared Spectroscopic
Parallel (WISP) Survey. Our total volume over this redshift range is $\sim 8
\times10^5$ Mpc$^3$, comparable to many of the narrowband surveys despite their
larger area coverage. We find two LAEs at $z=6.38$ and $6.44$ with line
luminosities of L$_{\mathrm{Ly}\alpha} \sim 4.7 \times 10^{43}$ erg s$^{-1}$,
putting them among the brightest LAEs discovered at these redshifts. Taking
advantage of the broad spectral coverage of WISP, we are able to rule out
almost all lower-redshift contaminants. The WISP LAEs have a high number
density of $7.7\times10^{-6}$ Mpc$^{-3}$. We argue that the LAEs reside in
Mpc-scale ionized bubbles that allow the Lyman-alpha photons to redshift out of
resonance before encountering the neutral IGM. We discuss possible ionizing
sources and conclude that the observed LAEs alone are not sufficient to ionize
the bubbles.