Radio Recombination Lines toward the S140/L1204

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Session 82 -- HII Regions
Display presentation, Wednesday, 11, 1995, 9:20am - 6:30pm

[82.04] Radio Recombination Lines toward the S140/L1204

G.T.Smirnov, R.L.Sorochenko (P.N.Lebedev Physical Institute), C.M.Walmsley (MPIfR) (P.N.Lebedev Physical Institute, Russia)

We have used the Effelsberg 100-m telescope to observe the hydrogen and carbon 165$\alpha$ and 166$\alpha$ radio recombination lines towards the S140/L1204 complex. In addition to the transitions known from earlier observations, we detect a feature due to ionized sulphur in the C\,{\sc ii}~region. On the basis of the observed H line parameters, we conclude that the emission nebula S140 is only a part of a larger partially obscured H\,{\sc ii}~region which has an electron temperature of 6400~K and an electron density of order 10~cm$^{-3}$. The obscured fraction of the H\,{\sc ii}~region appears to be either behind or partially immersed in the molecular and C\,{\sc ii}~regions. We derive parameters for the C\,{\sc ii}~region by combining our results with measurements of the C\,{\sc ii}~158~$\mu$m fine structure line and conclude that the temperature is in the range 75--200~K whereas the electron density is in the range 0.5--9~cm$^{-3}$. If there is pressure equilibrium between H\,{\sc ii} and C\,{\sc ii} gas, then the lower values of the temperature and density are preferable.

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