| Abstract : | Magnetohydrodynamic (MHD) turbulence in the Interstellar Medium (ISM) significantly affects its properties. But unfortunately, from an observational perspective, it is challenging to study turbulent properties of the diffuse ISM through standard HI 21-cm absorption or emission data. Turbulence-induced broadening of the spectral lines makes it difficult to infer the true physical properties from the spectral data. A relatively recent method proposed to tackle this problem involves the multi-gaussian decomposition of the HI spectrum to identify the different ISM components, and employ statistical properties of turbulence, like Larson-like scaling of velocity dispersion, to decouple the thermal and turbulent spectral line broadening. On the other hand, several MHD simulation-based studies on ISM turbulence, with various kinds of turbulence driving, have been conducted, involving the study of time evolution and the statistical properties of various physical parameters like pressure, temperature, and magnetic field. But little effort has been made to combine or compare simulation and observational results. In this work, we check how the results from observational and simulation data for diffuse ISM tally. We take both ISM MHD simulation data and actual 21-cm spectral data, pass them through the same analysis pipeline, and compare the results. We notice a mismatch between the expected and the observed outcomes. Further analysis shows that several assumptions about the gas in ISM, often made during studies of observational data, may not be correct and, thus, may lead to incorrect conclusions. We also identify shortcomings with simulation data and find that it may not correctly represent the ISM in terms of the turbulence properties. Further, we modify the existing analysis methodologies and create a better data analysis pipeline. |
