Exploring the effect of protostellar feedback on star formation and molecular cloud dynamics
Creators: name: Appel, Sabrina Marbut
Publisher: name: No Publisher Supplied
Year: 2024

description: Star formation is a fundamental building block of astrophysics and plays an important role in processes ranging from galaxy formation and evolution to the formation of proto-planetary disks. A variety of cloud-scale physical mechanisms contribute to the process of star formation, including: collapse due to self-gravity, supersonic turbulence, magnetic fields, and stellar feedback. In this dissertation, I present my work using 3D magnetohydrodynamical simulations of star-forming regions and analytic models to study star formation. I first present my work using a suite of turbulent box simulations to study the shape and evolution of the density probability distribution function (PDF; Appel et al. 2022). We explore how the shape of the PDF evolves with the inclusion of different physical processes and as a function of time. In agreement with the model proposed in Burkhart (2018), we find that the inclusion of self-gravity produces a power-law tail at the high-density end of the PDF, while supersonic turbulence produces a lognormal shape near the mean density. We also find that the inclusion of protostellar jets produces non-lognormal, time-varying features at the low-density end of the PDF. We find that the amount of mass in the power-law tail portion of the PDF is constant in time, suggesting that, as stars form, the dense gas is rapidly replenished from the collapsing diffuse gas. I then present my work further exploring the gas dynamics in star-forming regions using the expansion and compression rates of the gas (Appel et al. 2023). We explore how the gas dynamics varies with the inclusion of different physical processes. We find that the inclusion of supersonic turbulence increases both the compression and expansion rates, resulting in an approximate equilibrium between compressing and expanding gas near the mean density. We find that self-gravity dominates the gas dynamics at the highest densities and that the inclusion of protostellar jets produces rapidly expanding and compressing gas at low densities. We also compare the gas dynamics to the star formation rate (SFR) using the net gas mass flux. We find that the net gas mass flux matches the SFR at densities above where the PDF begins to form a power-law distribution but below the sink formation threshold. This suggests that the gas dynamics at this density plays a role in setting the SFR. Finally, I present my work with Torch (Appel et al. in prep.), a numerical framework optimized for simulating the formation and evolution of stellar clusters. Previous work with Torch has explored a variety of questions related to star formation and includes the impact of several modes of stellar feedback, including stellar winds, radiative feedback, and supernovae. However, previous work with Torch has not included the impact of protostellar jets, which has been demonstrated to play an important role in star formation. We have now implemented a new module within the Torch framework for including the impact of protostellar jets. We present this new module as well as preliminary results from the first Torch runs to include jets. We find that the inclusion of protostellar jets slows star formation even in star-forming regions up to 2 X 10^4 M_sun and that our lower mass clouds (5 X 10^3 M_sun) are sensitive to the star formation prescription and chosen jet parameters.