| Name: | Khushbu K. |
| Affiliation: | Indian Institute of Astrophysics |
| Conference ID: | ASI2025_201 |
| Title: | Self-consistent modelling of the ionized and neutral gas in PN NGC 6445 |
| Authors: | K. Khushbu 1, C. Muthumariappan 1 |
| Authors Affiliation: | 1 K. Khushbu, C. Muthumariappan Indian Institute of Astrophysics, Bangalore - 560034, India |
| Mode of Presentation: | Oral |
| Abstract Category: | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract: | Planetary nebulae (PNe) are the expanding envelopes of ionized gas and dust ejected by low-to-intermediate mass stars (1-8 M☉) during their final evolutionary stages. Beyond the ionized region where the Lyman 𝛼 photons decline, a transitional interface exists between the ionized and atomic regions. This interface has photons of energy range 6 -13.6 eV, which heat and dissociate the region by driving various chemical reactions known as photo-dissociation regions (PDRs). The ionization front is dynamic in PNe because the radius of the Strömgren sphere is significantly larger than the entire optical size of the nebula. As a result, the radiations become trapped, preventing the system from reaching equilibrium.
This study focuses on PN NGC 6445, a typical H-rich central star PN with thick PDR and molecular signatures, which allow for a comprehensive model of both photo-ionized regions and PDRs using detailed spectroscopic data. We have used the multiwavelength data ranging from UV to IR, encompassing UV archival data from IUE to account for the photo-electric heating by the very small grains (VSGs), Optical spectroscopic data from HCT-HFOSC spectrograph at two position angles (45 & 90 degrees anticlockwise), and IR data from Spitzer IRS and Herschel. To accurately constrain the central star parameters, we used the 1D Dusty photo-ionization model, integrating the CLOUDY 23.01 spectral synthesis code with the Rauch stellar model atmosphere. We optimized the ionized and neutral gas by defining a density function and variation in the filling factor. Our self-consistent model traps the ionization front effectively at a particular snapshot. The model incorporates two-grain size distributions (MRN and KMH) to study the effects of quantum heating by VSGs. Such a detailed analysis is crucial for understanding stellar evolution and the complex processes occurring within PNe. |
