  We mapped two molecular cloud cores in the Orion A cloud with the ALMA ACA
7-m Array and with the Nobeyama 45-m radio telescope. These cores have bright
N$_2$D$^+$ emission in single-pointing observations with the Nobeyama 45-m
radio telescope, have relatively high deuterium fraction, and are thought to be
close to the onset of star formation. One is a star-forming core, and the other
is starless. These cores are located along filaments observed in N$_2$H$^+$,
and show narrow linewidths of 0.41 km s$^{-1}$ and 0.45 km s$^{-1}$ in
N$_2$D$^+$, respectively, with the Nobeyama 45-m telescope. Both cores were
detected with the ALMA ACA 7m Array in the continuum and molecular lines at
Band 6. The starless core G211 shows clumpy structure with several sub-cores,
which in turn show chemical differences. Also, the sub-cores in G211 have
internal motions that are almost purely thermal. The starless sub-core G211D,
in particular, shows a hint of the inverse P Cygni profile, suggesting infall
motion. The star-forming core G210 shows an interesting spatial feature of two
N$_2$D$^+$ peaks of similar intensity and radial velocity located symmetrically
with respect to the single dust continuum peak. One interpretation is that the
two N$_2$D$^+$ peaks represent an edge-on pseudo-disk. The CO outflow lobes,
however, are not directed perpendicular to the line connecting both N$_2$D$^+$
peaks.

Astrophysics of Galaxies