The Green Bank Ammonia Survey: Observations of Hierarchical Dense Gas
  Structures in Cepheus-L1251
  We use Green Bank Ammonia Survey observations of NH$_3$ (1,1) and (2,2)
emission with 32'' FWHM resolution from a ~ 10 pc$^{2}$ portion of the
Cepheus-L1251 molecular cloud to identify hierarchical dense gas structures.
Our dendrogram analysis of the NH$_3$ data results in 22 top-level structures,
which reside within 13 lower-level, parent structures. The structures are
compact (0.01 pc $\lesssim R_{eff} \lesssim$ 0.1 pc) and are spatially
correlated with the highest H$_2$ column density portions of the cloud. We also
compare the ammonia data to a catalog of dense cores identified by
higher-resolution (18.2'' FWHM) Herschel Space Observatory observations of dust
continuum emission from Cepheus-L1251. Maps of kinetic gas temperature,
velocity dispersion, and NH$_3$ column density, derived from detailed modeling
of the NH$_3$ data, are used to investigate the stability and chemistry of the
ammonia-identified and Herschel-identified structures. We show that the dust
and dense gas in the structures have similar temperatures, with median
$T_{dust}$ and $T_K$ measurements of 11.7 $\pm$ 1.1 K and 10.3 $\pm$ 2.0 K,
respectively. Based on a virial analysis, we find that the ammonia-identified
structures are gravitationally dominated, yet may be in or near a state of
virial equilibrium. Meanwhile, the majority of the Herschel-identified dense
cores appear to be not bound by their own gravity and instead confined by
external pressure. CCS $(2_0-1_0)$ and HC$_5$N $(9-8)$ emission from the region
reveal broader line widths and centroid velocity offsets when compared to the
NH$_3$ (1,1) emission in some cases, likely due to these carbon-based molecules
tracing the turbulent outer layers of the dense cores.
