Gas and dust in a submillimeter galaxy at z = 4.24 from the Herschel
  ATLAS
  We report ground-based follow-up observations of the exceptional source,
ID141, one the brightest sources detected so far in the H-ATLAS cosmological
survey. ID141 was observed using the IRAM 30-meter telescope and Plateau de
Bure interferometer (PdBI), the Submillimeter Array (SMA) and the Atacama
Pathfinder Experiment (APEX) submillimeter telescope to measure the dust
continuum and emission lines of the main isotope of carbon monoxide and carbon
([C I] and [C II]). The detection of strong CO emission lines with the PdBI
confirms that ID141 is at high redshift (z=4.243 +/- 0.001). The strength of
the continuum and emission lines suggests that ID141 is gravitationally lensed.
The width (Delta V (FWHM) ~ 800 km/s}) and asymmetric profiles of the CO and
carbon lines indicate orbital motion in a disc or a merger. The properties
derived for ID141 are compatible with a ultraluminous (L_FIR ~ 8.5 +/- 0.3 x
10^13/mu_L Lsun, where mu_L is the amplification factor, dense (n ~ 10^4 cm^-3)
and warm (T_kin ~ 40K) starburst galaxy, with an estimated star-formation rate
of (0.7 to 1.7) x 10^4/mu_L Msun/yr. The carbon emission lines indicate a dense
(n ~ 10^4 cm^-3) Photo-Dominated Region, illuminated by a far-UV radiation
field a few thousand times more intense than that in our Galaxy. In conclusion,
the physical properties of the high-z galaxy, ID141, are remarkably similar to
those of local ultraluminous infrared galaxies.
