Discovery of a strong ionized-gas outflow in an AKARI-selected
  Ultra-luminous Infrared Galaxy at z = 0.5
  In order to construct a sample of ultra-luminous infrared galaxies (ULIRGs,
with infrared luminosity, $L_{\rm IR} > 10^{12}$ L$_{\odot}$) at 0.5 < z < 1,
we are conducting an optical follow-up program for bright 90-$\mu$m FIR sources
with a faint optical (i < 20) counterpart selected in the AKARI Far-Infrared
Surveyor (FIS) Bright Source catalog (Ver.2). AKARI-FIS-V2 J0916248+073034,
identified as a ULIRG at z = 0.49 in the spectroscopic follow-up observation,
indicates signatures of an extremely strong outflow in its emission line
profiles. Its [OIII] 5007\AA\ emission line shows FWHM of 1830 km s$^{-1}$ and
velocity shift of -770 km s$^{-1}$ in relative to the stellar absorption lines.
Furthermore, low-ionization [OII] 3726\AA\ 3729\AA\ doublet also shows large
FWHM of 910 km s$^{-1}$ and velocity shift of -380 km s$^{-1}$. After the
removal of an unresolved nuclear component, the long-slit spectroscopy 2D image
possibly shows that the outflow extends to radius of 4 kpc. The mass outflow
and energy ejection rates are estimated to be 500 M$_{\odot}$ yr$^{-1}$ and
$4\times10^{44}$ erg s$^{-1}$, respectively, which imply that the outflow is
among the most powerful ones observed in ULIRGs and QSOs at 0.3 < z < 1.6. The
co-existence of the strong outflow and intense star formation (star formation
rate of 990 M$_{\odot}$ yr$^{-1}$) indicates that the feedback of the strong
outflow has not severely affect the star-forming region of the galaxy.
