My research interests are centered around exploring the physics of star and planet formation with the aid of a mixture of numerical methods (e.g. N-body, SPH, hydrodynamic grid codes).
The objective of my thesis is:
to identify and understand the dominant physical processes that dictate disk properties and behavior.
More specifically, the main goals include:
- modeling disk formation in a top-down fashion, starting with cluster scales
- obtaining a set of initial conditions for the protostar populations within cluster environments, with and without magnetic fields.
- motivating the use of the cold (subvirial) collapse model of star cluster formation
- investigating the role of gravitational focusing in assembling clusters and setting the stellar IMF.
|Cold Collapse: a model of star (cluster) formation that assumes the sub-virial gravitational collapse of molecular clouds on global scales as the initial condition for star cluster formation.
We used the SPH code Gadget2 to simulate gravity driven star cluster formation from the progenitor molecular cloud. Motivated by observations of the ONC, we identify morphological and kinematic signatures of a “cold collapse” (initially sub-virial) model of star formation.
We analyse results from the 2015 model to identify kinematic and spatial substructure along the cluster and filament. We find similar structures to those identified by observations and explain their origins.
Gravitational focusing refers to a process in which mass accretion onto an object scales with the mass of the object.
Parametrizing the Bondi-Hoyle-Lyttleton (BHL) accretion as the accretion rate scaling with mass squared it is possible to show that the power-law tail in the stellar and star cluster mass functions can be grown by this process.
We explore the role of BHL accretion and, in effect, gravitational focusing, on the stellar IMF. We find that an isothermal SPH simulation of star cluster formation reproduces the Salpeter slope, as predicted by integrating the asymptotic limit of the BHL mass accretion formula.
Using hydrodynamic simulations run using Athena, with a sink-patch implementation, we track sink accretion and compare it to the sink’s mass and the mass of the sink’s environs – the adjacent cells referred to as the sink patch. Using a more relevant mass, we can easily see the effects of gravitational focusing in driving mass accretion onto the protostar and it’s role in setting the upper-mass stellar IMF.
We also present a semi-analytic toy model of BHL accretion to demonstrate its efficacy in growing a power law mass function over time: https://github.com/akuznetsova/BHL
We use an N-body code, ChaNga, to view star cluster formation on a more global scale, where we investigate whether the same principles we found for the stellar IMF apply for the scIMF.
Disk formation is a natural consequence of angular momentum in protostellar cores.
Understanding the nature of core angular momenta can not only help us create more realistic simulations of disk formation and evolution, but also contextualize observed disk populations.
We explore a parameter space of cloud rotation and random turbulent seeds using the hydrodynamic code Athena . Using a sink-patch implementation, we measure the specific angular momentum of protostellar cores on the core scale (0.05 pc – 0.1 pc) and find that angular momentum uses consistently ~ 20-30% of the available angular momentum budget. The accretion of angular momentum is found to be episodic, variable, and highly directional. We speculate that a local process must set the angular momentum of protostellar cores at early times – likely some form of gravitational torques.