(Left a) The T_e* derived from RRL and continuum data observed with the VLA in C and D array configuration at 10 GHz, assuming the electrons are under the LTE condition and the density ratio of helium to hydrogen is 0.07. (Right b)|$\sigma _{{{\rm T}e}^{*}}$|⁠, the errors of the T_e* image derived from 1σ rms noises of the RRL and continuum images. The synthesized beam is marked as a filled ellipse in the bottom left of the plots.