The UV-continuum Properties of Lyα-selected Galaxies at z = 6.5

Abstract

We report the first space-based very deep near-infrared continuum observations of a uniform sample of z = 6.5 galaxies with log(L(Lyα)) = 42.5-43 erg s^-1 selected from narrowband line searches and with spectroscopically confirmed Lyα emission. The 1.4 μm Hubble Space Telescope WFC3 observations are deep enough (AB(1σ) = 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 Lyα emission is present in 24% of all galaxies with M _AB(1350 Å) < -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 Lyα galaxies are extended but small (size <1 kpc), and have star formation rates of approximately 10 M _sun yr^-1. We find a mean L(Lyα)/νL _ν at 1400 Å to be 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 Lyα line. All of the properties of the z = 6.5 sample appear to be very similar to those of Lyα emitters at lower redshifts.