HCN emission from the HII regions G75.78+0.34 and G75.77+0.34
  We present images for the 3.5 mm continuum and HCN(J=1-0) hyperfine line
emission from the surroundings of the HII regions G75.78+0.34 and G75.77+0.34
obtained with the Berkeley Illinois Maryland Association (BIMA) interferometer
using the D configuration at a spatial resolution of 18 arcsec and spectral
sampling of 0.34 km/s. The continuum emission of both objects is dominated by
free-free emission from the ionized gas surrounding the exciting stars. Dust
emission may contribute only a small fraction of the 3.5 mm continuum from
G75.78+0.34 and is negligible for G75.77+0.34. The high spectral resolution
reached by BIMA allowed us to separate the emission from each hyperfine
transition (F=1-1, F=2-1 and F=0-1), as well as to construct velocity channel
maps along each emission-line profile. The HCN flux distributions are similar
to those observed for the CO emission, but with some knots of high intensities
indicating that the HCN traces high density clouds not seen in CO. The HCN
hyperfine line ratios for both HII regions differ from those predicted
theoretically for Local Thermodynamic Equilibrium (LTE), probably due to
scattering of radiation processes. The velocity channels shows that the HCN
emission of G75.78+0.34 follows the bipolar molecular outflows previously
observed in CO. For G75.77+0.34, the outflowing gas contributes only a small
fraction of the HCN emission.
