| Abstract : | The physical properties of the interstellar medium (ISM) regulate star formation activity in star forming regions. To understand the exact role of these properties in star formation, it is crucial to constraint them from observations. The Orion nebula hosts a variety of objects, e.g. young star clusters, HII region, predominantly atomic photodissociation region (PDR) and layered ionized gases. Moreover, its close proximity (414 ± 7 pc) makes it an ideal target for studying vital properties and processes of the ISM in the star-forming region. We have utilized the enhanced capabilities of the upgraded Giant Metrewave Radio Telescope (uGMRT) to study the physical conditions of the ISM in the Orion HII region. In this talk, I will present results from the wide-band interferometric observations of the Orion nebula at unique low-frequency bands of uGMRT. We have produced deep continuum images with off-source RMS noise ~200 uJy from band-3 (300 MHz - 500 MHz) and band-4 (550 MHz 750MHz) of uGMRT. In-band spectral index maps have been produced from the individual band data using Multi Term- Multi Frequency Synthesis (MT-MFS) deconvolution. Also, a conventional broad-band spectral index map is obtained using two-band flux maps. From our spectral analysis, an indication of the presence of non-thermal radio emission, atypical of HII regions, is found in some parts of the nebula. Furthermore, a systematic test of the reliability of the spectral index values has been carried out from simulated uGMRT data to verify this result and to understand and explore the requirements for a reliable estimation of spectral index values. Results from this reliability study of the spectral index from simulated data are used to establish the possibility of some non-thermal physical process in the Orion HII region. |
