Tracing the reionization epoch with ALMA: [CII] emission in z~7 galaxies
  We present new results on [CII]158$\mu$ m emission from four galaxies in the
reionization epoch. These galaxies were previously confirmed to be at redshifts
between 6.6 and 7.15 from the presence of the Ly$\alpha$ emission line in their
spectra. The Ly$\alpha$ emission line is redshifted by 100-200 km/s compared to
the systemic redshift given by the [CII] line. These velocity offsets are
smaller than what is observed in z~3 Lyman break galaxies with similar UV
luminosities and emission line properties. Smaller velocity shifts reduce the
visibility of Ly$\alpha$ and hence somewhat alleviate the need for a very
neutral IGM at z~7 to explain the drop in the fraction of Ly$\alpha$ emitters
observed at this epoch.
  The galaxies show [CII] emission with L[CII]=0.6-1.6 x10$^8 L_\odot$: these
luminosities place them consistently below the SFR-L[CII] relation observed for
low redshift star forming and metal poor galaxies and also below z =5.5 Lyman
break galaxies with similar star formation rates. We argue that previous
undetections of [CII] in z~7 galaxies with similar or smaller star formation
rates are due to selection effects: previous targets were mostly strong
Ly$\alpha$ emitters and therefore probably metal poor systems, while our
galaxies are more representative of the general high redshift star forming
population .
