Special Seminars


"Understanding the Multiphase Nature of the Circumgalactic Medium"

Alankar Dutta (Indian Institute of Science, Bangalore)

The massive yet low density gas environment that surrounds the galactic disk and is gravitationally bound by the host dark matter potential, is referred to as the Circumgalactic medium (CGM hereafter). This gas reservoir can account for most of the baryonic content of a galaxy. This multiphase gaseous component is important in regulating feedback, metallicity and evolution of the morphology and chemical composition of the galaxy. In my talk, I’ll present our work on idealized models and simulations to answer a few key questions related to the structure and state of the CGM plasma. Observations of the CGM indicate that fastmoving cold gas (a few hundred km/s) are ubiquitous around galactic disk. The cold gas lifted from the interstellar medium (ISM) by starbursts or AGN activities, can possibly be accelerated in the expanding wind from these outflows. This motivates our recent work on the growth and survival of cold, dense structures/clumps in environments of hot, expanding outflows. Our idealized models, for the first time, consider the dynamic structure of the expanding background wind which pushes on to the cold clouds. In addition to this, I’ll briefly demonstrate a codebase that we are developing. Thisis a unified interface with a library of theoretical and empirical models of the large-scale structure of the CGM. Existing models can be easily called with different choices of parameters and generate observables (like column densities, emission spectra, etc) that can be directly compared. We believe that such a coding endeavour is timely and useful for the community, providing a means to compare across models and perform rapid prototyping. This library aims to expand more in future and serve to bridge the gap between modelling the CGM and its observations.