On the nature of H$\alpha$ emitters at $z \sim 2$ from the HiZELS
  survey: physical properties, Ly$\alpha$ escape fraction, and main sequence
  We present a detailed multi-wavelength study (from rest-frame UV to far-IR)
of narrow-band (NB) selected, star-forming (SF) H$\alpha$ emitters (HAEs) at $z
\sim 2.23$ taken from the High Redshift(Z) Emission Line Survey (HiZELS). We
find that HAEs have similar SED-derived properties and colors to $sBzK$
galaxies and probe a well-defined portion of the SF population at $z \sim 2$.
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 H$\alpha$ observations with matched, existing
Ly$\alpha$ data we determine that the Ly$\alpha$ escape fraction ($f_{\rm
esc}$) is low (only $\sim$ 4.5\% of HAEs show Ly$\alpha$ emission) and
decreases with increasing dust attenuation, UV 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. This indicates that dust and Ly$\alpha$ are not mutually exclusive.
Using different and completely independent measures of the total SFR we show
that the H$\alpha$ emission is an excellent tracer of star formation at $z \sim
2$ with deviations typically lower than 0.3 dex for individual galaxies. We
find that the slope and zero-point of the HAE main-sequence (MS) at $z \sim 2$
strongly depend on the dust correction method used to recover SFR, although
they are consistent with previous works when similar assumptions are made.
