Open Access

Table 1

Studied ammonia lines showing at least potential maser features.

Line ν Eup Species V Ref.
(J, K) (MHz) (K) (km s–1)
(5,2) 20371.450 406.7 para 57 1
(5,3) 21285.275 380.4 ortho 57 2
(5,4) 22653.022 343.3 para 54+57 3
(6,2) 18884.695 577.6 para 54 2
(6,3) 19757.538 551.3 ortho 57 4
(6,4) 20994.617 514.3 para 57 5
(6,6) 25056.025 408.1 ortho 45 6
(7,3) 18017.337 750.2 ortho 54 5
(7,4) 19218.465 713.5 para 54 2
(7,5) 20804.830 666.0 para 54 3
(7,6) 22924.940 607.8 ortho 45+50 2
(7,7) 25715.182 538.6 para 45+50 2
(8,5) 18808.507 893.3 para 54 2
(8,6) 20719.221 835.5 ortho 45+54 7
(9,6) 18499.390 1090.9 ortho 45–67 4
(9,7) 20735.452 1022.6 para 54 2
(9,8) 23657.471 943.3 para 54 3
(10,7) 18285.434 1306.1 para 54 2
(10,9) 24205.287 1137.6 ortho 45+50 2
(11,9) 21070.739 1449.9 ortho 45+50+54 7

Notes. Frequencies (column 2) and upper state energies, Eup (column 3), were taken from the Jet Propulsion Laboratory (JPL) molecular line catalog (Pickett et al. 1998) and the Cologne Database for Molecular Spectroscopy (CDMS; Müller et al. 2005; Endres et al. 2016). Differences between lower and upper state energies correspond to approximately 1 K. Column 4 provides the ammonia species (ortho or para), while column 5 shows the approximate velocities of the maser components. Note that the term 45 km s–1 has been taken from Henkel et al. (2013). Because of a positive velocity drift, actual velocities tend to be higher by typically 2–4 km s–1. The last column provides a reference to the first detection of the respective maser line in the interstellar medium. 1: This paper; 2: Henkel et al. (2013); 3: Mauersberger et al. (1987); 4: Madden et al. (1986); 5: Mei et al. (2020); 6: Beuther et al. (2007); 7: Walsh et al. (2007).

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