Using the 100-m Effelsberg telescope near Bonn/Germany, Kadirya Tursun, a PhD student supervised by Prof. Jarken Esimbek from Xinjiang Astronomical Observatory (XAO), along with their collaborators from Max Planck Institute of Radioastronomie and other institutions, have detected multiple ammonia transitions in W33 giant molecular cloud, and obtained the precise physical properties of the dense clumps inside the cloud.
This work was published in International astronomical journal Astronomy and Astrophysics (2022, A&A, 658, A34).
Giant molecular clouds are the main structural units of the interstellar medium, and the dense clumps are the sites of massive star formation.
The W33 giant molecular cloud has a large mass and high brightness, and contains six dense clumps including Main, Main1, A, A1, B and B1. It is only 7.8 light-years away from the Earth and is one of the closest giant molecular clouds to us, making it a good sample for observation and research.
The researchers calculated the kinematic temperature, column density, volume density, abundance and other physical parameters of the six dense clumps using the observed ammonia spectra lines.
The results showed that the ammonia column density and abundance of W33 Main were one order of magnitude lower than that of Main1 and other five dense clumps, and the six dense clumps were in different evolutionary stages.
Moreover, ammonia Tkin determinations suggest that the large temperature gradients may be present in the dense molecular gas of W33 Main, W33 A, and W33 B. Ammonia has either been formed in the gas-phase or has been formed on dust grains in a medium with ~20 K or more to then be released into the interstellar medium.
Integrated intensity maps of NH3 (1,1) (left), (2,2) (middle), and (3,3) (right) for the W33 Main and W33 Main1 regions.
Contact: Kadirya Tursun
Xinjiang Astronomical Observatory, Chinese Academy of Sciences
Email: kadirya@xao.ac.cn
Article link: https://doi.org/10.1051/0004-6361/202141937
