Research

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.

Results of a cold collapse simulation with the SPH code Gadget2. The free-fall time < 1 Myr for this Orion-like embedded cluster. Gas particles are shown in red with the forming sink (star) particles as green open circles.
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.

[arxiv:1510.08478]

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.

[arxiv:1709.07754]

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.

[arxiv:1506.02591]

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.

[arxiv:1810.03682]

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
DOI

[arxiv:1702.00279]

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.

An initially log-normal distribution of seed masses (in gray) can grow a power law tail if the accretion rate is proportional to the mass squared. Example from https://github.com/akuznetsova/BHL