Free-free Emission and Radio Recombination Lines from Photoevaporating
  Disks
  Recent infrared observations have demonstrated that photoevaporation driven
by high-energy photons from the central star contributes to the dispersal of
protoplanetary disks. Here, we show that photoevaporative winds should produce
a detectable free-free continuum emission given the range of stellar ionizing
photons and X-ray luminosities inferred for young sun-like stars. We point out
that VLA observations of the nearby disk around TWHya might have already
detected this emission at centimeter wavelengths and calculate the wind
electron density and mass flow rate. We also estimate the intensities of H
radio recombination lines tracing the wind and discuss which ones could be
detected with current instrumentation. The detection and profiles of these
recombination lines would unambiguously prove our inference of free-free
emission from photoevaporating disks like TWHya. In addition, radio/millimeter
data can help constraining wind parameters such as temperature and electron
density that are fundamental in measuring mass flow rates.
