PI: PRAKRITI PALCHOUDHURY
Title: Understanding large scale density features in the largest astrophysical entities in the Universe Resource allocation: CSD3 1. Characterising scales of coherent density features due to injected magnetized outflows into a magnetized intracluster medium – The origin and sustenance of a wide range of coherent structures in temperature and density observed in the high- resolution X-ray surface brightness maps of galaxy clusters is uncertain. There are some proposed physical mechanisms at small scales and at very large scales. The role of magnetic field in either is not clear yet most of these structures are also spatially anisotropic (usually attributed to magnetic field). We are designing three dimensional magnetohydrodynamic simulations to explore the formation and sustenance mechanisms of coherent features across the scales. As a first step, we now are ready to investigate the following question – if the feedback from black hole activities in the cluster centre is magnetized with a smaller plasma beta (ratio of thermal to magnetic energy) compared to the bulk gas in the surroundings, how do the thermal and magnetic energy spectra evolve across time and scales? Below we show a snapshot of our simulated galaxy cluster.
2. Latent thermal instability: first step to understand the true nature of heat transport in circumgalactic plasmas – There are fundamental physics questions in the applicability of classical energy transport theory developed in the 1960s. Around the same time, there has been a development in proposing the thermal instability mechanism by which a single temperature medium can saturate to a multiphase (multi- temperature) state. A key conclusion from latter is that, while thermal instability growth is scale-free (linear growth rate is dependent on background fluid properties solely), the natural smallest scales of cold clumps forming is the scale at which cooling and thermal conduction is balanced. This is referred to as the Field length. Following other major theoretical developments in thermal instability, the mechanism was eventually discussed in the context of H filaments in the core of clusters and more recently in the cold phase of circumgalactic plasmas. However, if classical theory fails, which it will in a weakly collisional and weakly (energetically) magnetized medium, the Field length is ill-defined. We are testing this fundamental physical issue using well- designed 1D conduction problem as a first step. We have revealed some previously unexplored results (to be published soon) . As a next step, we explore this in 3D.
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