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Fig. 3


Total intensity images of seven inversion transitions of NH3 as well as the CH3OH line, as observed toward NGC 7538 IRS1 with the JVLA B-array. Contours of the NH3 line absorption are overplotted on the continuum emission (black image) at the frequency corresponding to each line. The contours represent factors 1, 3, 6, 12,... (afterwards, they are spaced by 10) of 20 mJy beam-1, for all transitions. The images were integrated over the velocity range 71 km s-1 to 47 km s-1, covering only the main hyperfine component. The line to continuum ratio decreases from 0.7 for the (6, 6) transition to 0.1 for the (13, 13) line (Table 2). For the (6, 6), (7, 7), and (9, 9) lines we overplotted also the absorption from one pair of hyperfine components (red contours). The velocity resolution was smoothed to 0.4 km s-1 for all transitions. The images were constructed with a 0.′′04 pixel for all transitions. No flux cutoff was applied. The synthesized beams (0.′′170.′′33) are shown in the lower left corner of each panel (see Table 1). The lower state energy levels of transitions shown here are 4081947 K.

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