2020A&A...643A.178T

We surveyed the Aquila Rift complex including the Serpens South and W 40 regions in the NH₃ (1,1) and (2,2) transitions making use of the Nanshan 26-m telescope. Our observations cover an area of ∼1.5°x2.2° (11.4pcx16.7pc). The kinetic temperatures of the dense gas in the Aquila Rift complex obtained from NH₃ (2,2)/(1,1) ratios range from 8.9 to 35.0K with an average of 15.3±6.1K (errors are standard deviations of the mean). Low gas temperatures are associated with Serpens South ranging from 8.9 to 16.8K with an average of 12.3±1.7K, while dense gas in the W 40 region shows higher temperatures ranging from 17.7 to 35.0K with an average of 25.1±4.9K. A comparison of kinetic temperatures derived from para-NH₃ (2,2)/(1,1) against HiGal dust temperatures indicates that the gas and dust temperatures are in agreement in the low-mass-star formation region of Serpens South. In the high-mass-star formation region W 40, the measured gas kinetic temperatures are higher than those of the dust. The turbulent component of the velocity dispersion of NH₃ (1,1) is found to be positively correlated with the gas kinetic temperature, which indicates that the dense gas may be heated by dissipation of turbulent energy. For the fractional total-NH₃ (para+ortho) abundance obtained by a comparison with Herschel infrared continuum data representing dust emission, we find values from 0.1x10^–8 to 2.1x10^–7 with an average of 6.9(±4.5)x10^–8. Serpens South also shows a fractional total-NH₃ (para+ortho) abundance ranging from 0.2x10^–8 to 2.1x10^–7 with an average of 8.6(±3.8)x10^–8. In W 40, values are lower, between 0.1 and 4.3x10^–8 with an average of 1.6(±1.4)x10^–8. Weak velocity gradients demonstrate that the rotational energy is a negligible fraction of the gravitational energy. In W 40, gas and dust temperatures are not strongly dependent on the projected distance to the recently formed massive stars. Overall, the morphology of the mapped region is ring-like, with strong emission at lower and weak emission at higher Galactic longitudes. However, the presence of a physical connection between the two parts remains questionable.