Herschel reveals the obscured star formation in HiZELS H\alpha\ emitters
  at z=1.47
  We describe the far-infrared (FIR; rest-frame 8--1000\mu m) properties of a
sample of 443 H\alpha-selected star-forming galaxies in the COSMOS and UDS
fields detected by the HiZELS imaging survey. Sources are identified using
narrow-band filters in combination with broad-band photometry to uniformly
select H\alpha\ (and [OII] if available) emitters in a narrow redshift slice at
z = 1.47+/-0.02. We use a stacking approach in Spitzer, Herschel (from PEP and
HerMES surveys) and AzTEC images to describe their typical FIR properties. We
find that HiZELS galaxies with observed H\alpha\ luminosities of ~ 10^{8.1-9.1}
Lo have bolometric FIR luminosities of typical LIRGs, L_FIR ~ 10^{11.48+/-0.05}
Lo. Combining the H\alpha\ and FIR luminosities, we derive median SFR = 32+/-5
Mo/yr and H\alpha\ extinctions of A(H\alpha) = 1.0+/-0.2 mag. Perhaps
surprisingly, little difference is seen in typical HiZELS extinction levels
compared to local star-forming galaxies. We confirm previous empirical stellar
mass (M*) to A(H\alpha) relations and the little or no evolution up to z =
1.47. For HiZELS galaxies, we provide an empirical parametrisation of the SFR
as a function of (u-z)_rest colours and 3.6\mu m photometry. We find that the
observed H\alpha\ luminosity is a dominant SFR tracer when (u-z)_rest ~< 0.9
mag or when 3.6\mu m photometry > 22 mag (Vega) or when M* < 10^9.7 Mo. We do
not find any correlation between the [OII]/H\alpha\ and FIR luminosity,
suggesting that this emission line ratio does not trace the extinction of the
most obscured star-forming regions. The luminosity-limited HiZELS sample tends
to lie above of the so-called `main sequence' for star-forming galaxies,
especially at low M*. This work suggests that obscured star formation is linked
to the assembly of M*, with deeper potential wells in massive galaxies
providing dense, heavily obscured environments in which stars can form rapidly.
