Postdoctoral research (2022-ongoing)

Type Ia supernovae in ellipticals

We modeled small portions of the interstellar medium (ISM) of an elliptical galaxy using Athenak, and seeded type Ia supernovae (SNIa), that both heat the medium and drive turbulence in the ISM. We studied whether the SNIa can keep the ISM in a steady state, provided the heating balances the cooling. In our local patch simulations, we found the system always overheats once the cooling drops below the heating. We are currently performing global simulations of an isolated massive elliptical galaxy to study the long-term evolution of such a system with appropriate geometry.

Stratified Multiphase turbulence

We modeled a patch of the intracluster medium (ICM) using FLASH, driving turbulence and including radiative cooling. We derived a new condensation criterion for cold gas to condense out of the hot ICM, which takes into account the effects of both turbulent mixing and buoyant motions that prevent the formation of cold gas.

Publications

Multiphase Gas in Elliptical Galaxies: The Role of Type Ia Supernovae , Mohapatra R, Quataert E, APJ, 2024.

Multiphase condensation in cluster haloes: interplay of cooling, buoyancy, and mixing , Mohapatra R, Federrath C, Sharma P, Quataert E, MNRAS, 2023.

PhD thesis (2018-2022)

Multiphase turbulence

We performed local idealised simulations of gas in the intracluster medium using FLASH. We have studied the effect of the turbulence driving on gas prpoerties such as morphology and density, temperature distribution functions. We also study the different sources and sinks of enstrophy, i.e., solenoidal motions, as well as the kinematics of hot (∼ 107 K) X-ray emitting and cold (∼ 104 K) H𝛼 emitting gas.

In an earlier study, we studied the effect of varying levels of turbulent feedback on these different statistical properties of gas. We have also looked at the modes of perturbation of the gas, the interactions and transitions between different temperature phases. We have studied the effect of magnetic fields and two different idealised heating models. We find that a weakly turbulent feedback scenario best explains the observations of the multiphase ICM. The simulation movies are available as a youtube playlist.

In a companion study, we have studied the velocity structure functions (VSFs) in these high-resolution multiphase turbulence simulations, which are important in interpreting measurements of the kinematics of Hα filaments in cool core clusters. We have looked at VSFs of hot and cold temperature phases separately and studied the effect of our two idealised heating models (mass-weighted vs volume-weighted) magnetic fields. We have also discussed the effect of projection along the line of sight on the VSFs of hot and cold phase gas and compared them with recent observations.

Publications

Multiphase turbulence in galactic halos: effect of the driving, Mohapatra R, Federrath C, Sharma P, MNRAS, 2022.

Velocity structure functions in multiphase turbulence: interpreting kinematics of Hα filaments in cool core clusters, Mohapatra R, Jetti M, Sharma P, Federrath C, MNRAS, 2022.

Characterizing the turbulent multiphase halos with periodic box simulations , Mohapatra R, Jetti M, Sharma P, Federrath C, MNRAS, 2022.

Stratified turbulence

We studied the effect of stratification on turbulence and its implications to the ICM. We derived a new scaling relation between the amplitude of density fluctuations, the degree of stratification (denoted by the Froude number) and the rms Mach number of the flow. We found the pressure fluctuations to be independent of the degree of stratification. In observations of galaxy clusters, the density and pressure variations show up as fluctuations in the X-ray surface brightness and the thermal Sunyaev-Zeldovich effect, respectively.

Publications

Turbulent density and pressure fluctuations in the stratified intracluster medium , Mohapatra R, Federrath C, Sharma P, MNRAS, 2021.

Turbulence in stratified atmospheres: implications for the intracluster medium , Mohapatra R, Federrath C, Sharma P, MNRAS, 2020.

Bachelor thesis (2017-2018)

We used PLUTO to simulate gas in the intracluster medium. We studied the importance of turbulent heating in achieving thermal balance in cool cluster cores.

The simulation movies are available at bachelor thesis movies and also as a youtube playlist.

Publications

Turbulence in the intracluster medium: simulations, observables & thermodynamics, Mohapatra R, Sharma P, MNRAS, 2019.