Ajay Gill & Shaunak Mondak

Ajay Gill (MIT AeroAstro)

Title: A study of galaxy clusters and filaments with the Sunyaev–Zeldovich effect using multifrequency cosmic microwave background observations
Abstract: Galaxy clusters are the largest gravitationally bound objects in the universe. Their study probes the evolution of large-scale structure in the universe. I will discuss a new methodology to study the thermal and kinematic properties of galaxy clusters with cosmic microwave background (CMB) observations. The hot electrons and the bulk motion of clusters modify CMB photons as they pass through the clusters, leading to the so-called thermal and kinematic Sunyaev–Zeldovich (SZ) effects, respectively. My approach relies on using CMB temperature maps from multiple instruments at different frequencies to simultaneously fit for both the tSZ and kSZ effects, while accounting for relativistic corrections and modelling foregrounds such as dust emission. I will demonstrate the success of this approach by applying it to the Abell 399–401 galaxy cluster pair and filament system using data from the Atacama Cosmology Telescope and the Planck satellite.

Shaunak Mondak (Princeton University)​

Title: Stellar Dynamics in a Fluctuating Interstellar Medium
Abstract: The interstellar medium (ISM) plays an important role in sculpting the structure of our Galaxy: in addition to being the birthplaces of stars, ISM substructures have the capacity to significantly perturb stellar orbits. Accounting for the ISM’s influence is important for drawing robust conclusions about the Milky Way’s dynamical history and dark matter substructure. However, conventional stellar-dynamical studies often rely on idealized toy models or omit these gas “fluctuations” entirely, leaving their impact on the evolution of stellar systems poorly understood. In this talk, I will present a model for ISM fluctuations that is both theoretically tractable and easily incorporated into N-body simulations, while retaining the essential features of a realistic ISM. The model is derived from a characterization of the ISM in the state-of-the-art TIGRESS MHD simulations, which include self-consistent, first-principles gas microphysics and resolve scales down to 2 pc. I will then highlight several key differences between the dynamical effects of these realistic fluctuations and those assumed in prevailing models, focusing on heating and radial migration in galactic disks.