Recently, researchers from the Xinjiang Astronomical Observatory of the Chinese Academy of Sciences presented observations of the Aquila giant molecular cloud using the NanShan 26 m Radio Telescope and the Delingha 13.7 m millimeter -wavelength telescope.
They analyzed the distribution of NH3, 12CO, 13CO, and C18O, as well as the spectral line parameters, to derive the associated physical parameters. This work was published in Research in Astronomy and Astrophysics.
It is widely recognized that carbon-chain molecules are depleted from the gas phase in the central regions of the molecular cores due to their freeze-out onto dust grains. As a result, carbon-bearing molecules are typically found in the outer regions of the molecular cores. Conversely, nitrogen-bearing molecules like ammonia are concentrated in the inner cores, where the gas density reaches approximately 105 cm−3.
In addition, ammonia remains detectable in the gas phase because it is resistant to depletion onto dust grains. Therefore, these three lines share some common attributes while also exhibiting distinct characteristics.
The study shows that the CO gas distribution is similar to the NH3 gas distribution in the Aquila Rift cloud complex. By comparing the spectral line parameters of NH3, 13CO, and C18O, the researchers revealed that the line center velocities of these NH3, 13CO, and C18O are comparable and positively correlated, indicating that they originate from the same emission region. However, no significant correlation was identified for other parameters, including integrated intensity, line widths, main beam brightness temperature, and the column densities of NH3, 13CO, and C18O.
This research work was supported by the National Key R&D Programs of China, the Tianchi Talent Project of Xinjiang Uyghur Autonomous Region, and the Natural Science Foundation of Xinjiang Uyghur Autonomous Region.
Fig.1. The composite maps of integrated intensity of colored 12CO (left) with the contour lines NH3 (1,1), colored 13CO (middle) with the contour lines NH3 (1,1), and colored C18O (right) with the contour lines NH3 (1,1) in the Aquila Rift cloud complex.
Fig.2. Left: Correlation between the line center velocities of NH3 (1,1) and 13CO, C18O lines at corresponding points in the Aquila Rift cloud complex. Right: Histograms showing the distributions of measured line center velocity for NH3 (1,1), 13CO, and C18O.
