  The VLA has been used at 8.3 GHz in the DnC and CnB array configurations to
carry out an H92alpha recombination line study (at 8.3 GHz) of the ionized gas
in the Arched Filaments H II complex, which defines the western edge of the
Galactic center Radio Arc. The H92alpha line properties of the ionized gas are
consistent with photoionization from hot stars,and consistent with the physical
properties of other Galactic center H II regions. The LTE electron temperatures
vary only slightly across the entire extent of the source, and have an average
value of 6200 K. The velocity field is very complex, with velocities ranging
from +15 to - 70 km/s and the majority of velocities having negative values.
Large velocity gradients (2-7 km/s/pc, with gradients in some regions >10
km/s/pc) occur along each of the filaments, with the velocities becoming
increasingly negative with decreasing distance from the Galactic center. The
magnitudes of the velocity gradient are consistent with the cloud residing on
an inner, elongated orbit which is due to the Galaxy's stellar bar, or with a
radially infalling cloud. The ionization of the Arched Filaments can be
accounted for completely by the massive Arches stellar cluster, which consists
of > 150 O-stars. This cluster is likely to belocated 10-20 pc from the Arched
Filaments, which can explain the uniformity of ionization conditions in the
ionized gas.
