| Abstract : | Observation from various infrared space telescopes (Spitzer, IRAS, and ISO, etc.) show the mid-infrared emission features at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 µm are ubiquitous. They are present in HII regions, reflection nebula, post-AGB stars, planetary nebulae, and external galaxies. These emission bands are related to the vibrational transitions in aromatic molecules such as polycyclic aromatic hydrocarbon (PAH). Hence, these bands are also known as Aromatic Infrared Bands (AIBs). There are feature variations from source to source, indicating different PAHs in different objects. To understand the complex chemistry and physical conditions leading to these differences, we attempt to study a variety of astrophysical objects in IR bands. In this work, we report the high-resolution infrared imaging results of two planetary nebulae (NGC 6543 and NGC 6826), two reflection nebulae (NGC 2023 and NGC 7023), an HII region (AFGL 437), and a post-AGB star (IRAS 22272+5435). The near-IR observations were taken from TIFR Infrared Camera-II (TRICAM2) on 3.6 m Devasthal Optical Telescope (DOT). The near-IR observations were performed in J, H, K, PAH, and nbl (narrow-band L) filters, with wavelengths centred at 1.20, 1.65, 2.19, 3.28, and 3.59 µm, respectively. The 3.28 µm AIB is a significant band arising due to the C-H stretching vibration in PAHs. Its observations confirm the existence of PAH molecules in the line of sight and give insight into the location and environment where PAHs are present. Analysis shows emissions from warm dust and PAHs in the circumstellar shells of the source. We also attempted to interpret these observational results in terms of the properties of the PAH population (e.g., change in size, shape, charge, and composition). IR Imaging of these objects is among the first observation in the PAH band from the ground-based telescope. The near-IR band morphologies of these objects are discussed and compared with the optical bands. |
