An In-Depth Survey of NGC6445 and its Chemical Composition

During the AGB phase of a star, the atmosphere cools enough to allow for the formation of molecules in great abundance within the star’s circumstellar envelope. According to simulations, these molecules were thought to be destroyed within 1000 years of the PN phase due to the high levels of energetic radiation. However, recent surveys revealed that PNe contain a surprising amount of molecular material, including polyatomics. These molecules may survive the intense UV radiation during the PN phase due to shielding from dense dusty globules. This process would allow PNe to contribute molecular material to the ISM. During one of these recent surveys, NGC 6445 was noted as a source of interest due to its strong molecular lines which displayed structural complexity. In the interest of exploring the molecular composition of this object in more depth, a detailed molecular survey was conducted on NGC 6445 through the Institut de Radioastronomie Millimétrique (IRAM) 30m as well as the Arizona Radio Observatory (ARO) 12m at 2–3 mm in wavelength. These observations revealed a few common compounds like HCN, HNC, HCO⁺, and CO, as well as more complex polyatomic molecules such as c-C₃H₂, CCH, H¹³CN, and HC₃N. Within the survey, the J = 11 → 10 transition of C₃N^- was also potentially detected in this source. If confirmed, C₃N^-would be the first identification of an anion in PNe. The data were analyzed by Gaussian fitting, which required roughly three components to account for the complex velocity structure of each line: one red-shifted, one blue-shifted, and one central component. Subsequently, the radiative transfer program RADEX was used in order to determine the relative abundances of the molecules. These RADEX models are ongoing and will be continued in our future work. Additionally, we plan to confirm the presence of C₃N⁻ by observing another transition of this molecule in NGC 6445.