The 2nd Generation z(Redshift) and Early Universe Spectrometer Part I:
  First-light observation of a highly lensed local-ULIRG analog at high-z
  We report first science results from our new spectrometer, the 2nd generation
z(Redshift) and Early Universe Spectrometer (ZEUS-2), recently commissioned on
the Atacama Pathfinder Experiment telescope (APEX). ZEUS-2 is a submillimeter
grating spectrometer optimized for detecting the faint and broad lines from
distant galaxies that are redshifted into the telluric windows from 200 to 850
microns. It utilizes a focal plane array of transition-edge sensed bolometers,
the first use of these arrays for astrophysical spectroscopy. ZEUS-2 promises
to be an important tool for studying galaxies in the years to come due to its
synergy with ALMA and its capabilities in the short submillimeter windows that
are unique in the post Herschel era. Here we report on our first detection of
the [CII] 158 $\mu m$ line with ZEUS-2. We detect the line at z ~ 1.8 from
H-ATLAS J091043.1-000322 with a line flux of $(6.44 \pm 0.42) \times 10^{-18} W
m^{-2}$. Combined with its far-infrared luminosity and a new Herschel-PACS
detection of the [OI] 63 $\mu m $ line we model the line emission as coming
from a photo-dissociation region with far-ultraviolet radiation field, $G
\approx 2 \times 10^{4} G_{0}$, gas density, $n \approx 1 \times 10^{3}
cm^{-3}$ and size between ~ 0.4 and 1 kpc. Based on this model, we conclude
that H-ATLAS J091043.1-000322 is a high redshift analogue of a local
ultra-luminous infrared galaxy, i.e. it is likely the site of a compact
starburst due to a major merger. Further identification of these merging
systems is important for constraining galaxy formation and evolution models.
