ALMA [O III] and [C II] Detections of A1689-zD1 at $z=7.13$
  A1689-zD1 is one of the most distant galaxies, discovered with the aid of
gravitational lensing, providing us with an important opportunity to study
galaxy formation in the very early Universe. In this study, we report the
detection of [C II]158$\mu$m and [O III]88$\mu$m emission lines of A1689-zD1 in
the ALMA Bands 6 and 8. We measure the redshift of this galaxy as
$z_{\rm{sys}}=7.133\pm0.005$ based on the [C II] and [O III] emission lines,
consistent with that adopted by Bakx et al. (2021). The observed
$L_{[\rm{O\,III]}}/L_{[\rm{C\,II]}}$ ratio is $2.09\pm0.09$, higher than most
of the local galaxies, but consistent with other $z\sim7$ galaxies. The
moderate-spatial resolution of ALMA data provided us with a precious
opportunity to investigate spatial variation of
$L_{[\rm{O\,III]}}/L_{[\rm{C\,II]}}$. In contrast to the average value of 2.09,
we find a much higher $L_{[\rm{O\,III]}}/L_{[\rm{C\,II]}}$ of $\sim 7$ at the
center of the galaxy. This spatial variation of
$L_{[\rm{O\,III]}}/L_{[\rm{C\,II]}}$ was seldom reported for other high-z
galaxies. It is also interesting that the peak of the ratio does not overlap
with optical peaks. Possible physical reasons include a central AGN, shock
heating from merging, and starburst. Our moderate-spatial resolution data also
reveals that in addition to the observed two clumps shown in previous HST
images, there is a redshifted segment to the west of the northern optical
clump. Such a structure is consistent with previous claims that A1689-zD1 is a
merging galaxy, but with the northern redshifted part being some ejected
materials, or that the northern redshifted materials being from a third more
highly obscured region of the galaxy.
