Observational Results of a Multi-Telescope Campaign in Search of
  Interstellar Urea [(NH$_2$)$_2$CO]
  In this paper, we present the results of an observational search for gas
phase urea [(NH$_2$)$_2$CO] observed towards the Sgr B2(N-LMH) region. We show
data covering urea transitions from $\sim$100 GHz to 250 GHz from five
different observational facilities: BIMA, CARMA, the NRAO 12 m telescope, the
IRAM 30 m telescope, and SEST. The results show that the features ascribed to
urea can be reproduced across the entire observed bandwidth and all facilities
by best fit column density, temperature, and source size parameters which vary
by less than a factor of 2 between observations merely by adjusting for
telescope-specific parameters. Interferometric observations show that the
emission arising from these transitions is cospatial and compact, consistent
with the derived source sizes and emission from a single species. Despite this
evidence, the spectral complexity, both of (NH$_2$)$_2$CO and of Sgr B2(N),
makes the definitive identification of this molecule challenging. We present
observational spectra, laboratory data, and models, and discuss our results in
the context of a possible molecular detection of urea.
