On the nature of Ha emitters at z ∼ 2 from the HiZELS survey: physical properties, Lyα escape fraction and main sequence

We present a detailed multiwavelength study (from rest-frame ultraviolet to far-infrared) of narrow-band selected, star-forming (SF) Ha emitters (HAEs) at z similar to 2.23 taken from the High-Redshift(Z) Emission Line Survey (HiZELS). We find that HAEs have similar properties and colours derived from spectral energy distributions as sBzK galaxies, and probe a well-defined portion of the SF population at z similar to 2. This is not true for Ly alpha emitters (LAEs), which are strongly biased towards blue, less massive galaxies (missing a significant percentage of the SF population). Combining our Ha observations with matched, existing Ly alpha data, we determine that the Ly alpha escape fraction (f(esc)) is low (only similar to 4.5 per cent of HAEs show Ly alpha emission) and decreases with increasing dust attenuation, ultraviolet continuum slope, stellar mass and star formation rate (SFR). This suggests that Ly alpha preferentially escapes from blue galaxies with low dust attenuation. However, a small population of red and massive LAEs is also present, in agreement with previous works and indicating that dust and Ly alpha are not mutually exclusive. Using different and completely independent measures of the total SFR, we show that the Ha emission is an excellent tracer of star formation at z similar to 2 with deviations typically lower than 0.3 dex for individual galaxies. We find that the slope and zero-point of the HAE main sequence at z similar to 2 strongly depend on the dust-correction method used to recover the SFR, although they are consistent with previous works when similar assumptions are made.