The UV-continuum properties of Ly alpha selected galaxies at z=6.5
  We report the first space-based very deep near-infrared continuum
observations of a uniform sample of z = 6.5 galaxies with log(L(L_alpha)) =
42.5 - 43 erg/s selected from narrow-band line searches and with
spectroscopically confirmed Ly alpha emission. The 1.4 micron HST WFC3
observations are deep enough (AB(1 sigma) = 28.75) to measure individual
continuum magnitudes at this redshift for all of the objects. We compare the
results with continuum-selected samples at the same redshift and find that Ly
alpha emission is present in 24% of all galaxies with M_AB(1350 A) < -20 at z =
6.5. The error in this quantity is dominated by systematic uncertainties, which
could be as large as multiplicative factors of three. The Ly alpha galaxies are
extended but small (size < 1 kpc), and have star formation rates of
approximately 10 Msun/yr. We find a mean L(Ly alpha)/(nu L_nu) at 1400A of
0.08, with the seven objects showing a range from 0.026 to 0.26, implying that
there is little sign of destruction of the Ly alpha line. All of the properties
of the z = 6.5 sample appear to be very similar to those of Ly alpha emitters
at lower redshifts.
