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Fig. 4


Spectral profiles of the thermal (and maser) emission from the metastable NH3 (6, 6), (7, 7), (9, 9), (10, 10), and (13, 13) inversion transitions, integrated in a region with size of 0.̋8 around the maser position. The spectra shown here are the same as in Fig. 3, but with a narrower flux density and a wider velocity range to highlight the weaker thermal emission. The vertical dashed line indicates a velocity of 60 km s-1. The velocity resolution is 0.4 km s-1. We note that the hyperfine satellite lines (separated by ~ ± 27 − 31 km s-1) are clearly detected for the (6, 6) line (indicated with black vertical lines), but they are also still visible in the (7, 7) spectrum. The upper state energy levels of transitions shown here are ~4081691 K (see Table 1).

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