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We present the results of Magellan/MMIRS and Keck/NIRSPEC spectroscopy for five Lya emitters (LAEs) at z=2. 2 for which high-resolution FUV spectra from Magellan/MagE are available. We detect nebular emission lines including Ha on the individual basis and low-ionization interstellar (LIS) absorption lines in a stacked FUV spectrum, and measure average offset velocities of the Lya line, DeltaᵥLya, and LIS absorption lines, Deltaᵥₐbs, with respect to the systemic velocity defined by the nebular lines. For a sample of eight z~2-3 LAEs without AGN from our study and the literature, we obtain DeltaᵥLya = 175+/-35 km s^-1, which is significantly smaller than that of Lyman-break Galaxies (LBGs), DeltaᵥLya=400 km s^-1. The stacked FUV spectrum gives Deltaᵥₐbs = -179 +/- 73 km s^-1, comparable to that of LBGs. These positive DeltaᵥLya and negative Deltaᵥₐbs suggest that LAEs also have outflows. In contrast to LBGs, however, the LAEs' DeltaᵥLya is as small as |Deltaᵥₐbs|, suggesting low neutral hydrogen column densities. Such a low column density with a small number of resonant scattering may cause the observed strong Lya emission of LAEs. We find an anti-correlation between Lya equivalent width (EW) and DeltaᵥLya in a compilation of LAE and LBG samples. Although its physical origin is not clear, this anti-correlation result appears to challenge the hypothesis that a strong outflow, by means of a reduced number of resonant scattering, produces a large EW. If LAEs at z>6 have similarly small DeltaᵥLya values, constraints on the reionization history derived from the Lya transmissivity may need to be revised.
Hashimoto et al. (Fri,) studied this question.