ALMA Observation of 158 micron [CII] Line and Dust Continuum of a z=7
  Normally Star-forming Galaxy in the Epoch of Reionization
  We present ALMA observations of the [CII] line and far-infrared (FIR)
continuum of a normally star-forming galaxy in the reionization epoch, the
z=6.96 Ly-alpha emitter (LAE) IOK-1. Probing to sensitivities of sigma_line =
240 micro-Jy/beam (40 km/s channel) and sigma_cont = 21 micro-Jy/beam, we found
the galaxy undetected in both [CII] and continuum. Comparison of UV - FIR
spectral energy distribution (SED) of IOK-1, including our ALMA limit, with
those of several types of local galaxies (including the effects of the cosmic
microwave background, CMB, on the FIR continuum) suggests that IOK-1 is similar
to local dwarf/irregular galaxies in SED shape rather than highly
dusty/obscured galaxies. Moreover, our 3 sigma FIR continuum limit, corrected
for CMB effects, implies intrinsic dust mass M_dust < 6.4 x 10^7 M_sun, FIR
luminosity L_FIR < 3.7 x 10^{10} L_sun (42.5 - 122.5 micron), total IR
luminosity L_IR < 5.7 x 10^{10} L_sun (8 - 1000 micron) and dust-obscured star
formation rate (SFR) < 10 M_sun/yr, if we assume that IOK-1 has a dust
temperature and emissivity index typical of local dwarf galaxies. This SFR is
2.4 times lower than one estimated from the UV continuum, suggesting that < 29%
of the star formation is obscured by dust. Meanwhile, our 3 sigma [CII] flux
limit translates into [CII] luminosity, L_[CII] < 3.4 x 10^7 L_sun. Locations
of IOK-1 and previously observed LAEs on the L_[CII] vs. SFR and L_[CII]/L_FIR
vs. L_FIR diagrams imply that LAEs in the reionization epoch have significantly
lower gas and dust enrichment than AGN-powered systems and starbursts at
similar/lower redshifts, as well as local star-forming galaxies.
