Computational Astrophysics PhD Projects
Research projects on offer in our Simulations group:
A new cosmological residual distribution hydrodynamical solver
- Video: A new cosmological residual distribution hydrodynamical solver
- A new cosmological residual distribution hydrodynamical solver
This PhD project proposal aims at developing a new beyond the-state-of-the-art hydrodynamical simulation code. The student will be expected to develop code to implement numerical schemes based on the residual distribution method for highly parallel compute architectures. Emphasis will be put on scalability to a large number of compute nodes to allow for the next generation of cosmological simulations.
In current astrophysical simulations, two prevailing numerical methods are the Lagrangian-based Smoothed Particle Hydrodynamics (SPH) and the Eulerian-based structured-mesh hydrodynamics, often with adaptive mesh capabilities. SPH codes have exceptional adaptive spatial resolution capabilities, as the particles naturally sample the denser regions of the fluid flow. This comes at the cost, however, of poor shock resolution and the suppression of instabilities at contact discontinuities when compared to mesh-based codes. Cartesian mesh-based codes capture shocks and entropy mixing better, however, they also suffer drawbacks in resolution (even if using adaptive mesh capabilities) and in poorly resolved bulk flows due to the lack of a Galilean-invariant formulation. As has been noted, many of the drawbacks of both SPH and cartesian mesh-based codes can be eliminated if the mesh is allowed to move with the fluid in an arbitrary Lagrange-Eulerian approach.
Much research has been done to identify a true multi-dimensional upwind scheme over the past few decades. One promising scheme is the residual distribution (RD) method. This method combines many of the advantages of a finite volume method with a genuinely multi-dimensional solution to the hydrodynamical equations. During the project, the student will implement such a hydrodynamical solver and investigate its impact on physical processes in the early Universe.
Precision cosmology with the Lyman-Alpha forest
Intergalactic space is filled with a pervasive medium of ionized gas, the Intergalactic Medium (IGM). Detections of the IGM in the spectra of high redshift quasars reveal a highly fluctuating medium: the Lyman-Alpha forest. The statistics of the fluctuations are well-reproduced by numerical simulations involving dark matter and baryons. As such, the IGM offers an opportunity to probe the primordial density fluctuations on scales unavailable to other methods.
This project will involve the student in numerical cosmological simulations of the IGM to investigate the expected shape of the Lyman-Alpha forest flux power spectrum and its relation to the dark matter primordial power spectrum. The student will be a member of a group involved in cosmological structure simulations at the Edinburgh Centre for Computational Astrophysics (http://www.roe.ac.uk/~aam/ecca).
Building Galaxies at Cosmic Dawn
The formation of the first generation of stars marked the beginning of the era known as Cosmic Dawn. This occurred in the first few hundred million years after the Big Bang. Theory and observation both suggest that the first stars were likely much more massive than the stars we observe today. This is due to the fact that they formed out of primordial gas created in the Big Bang, which contained only hydrogen and helium, but none of the heavier elements (like carbon, oxygen, iron, etc.) that are crucial to and ubiquitous in the modern Universe. The supernovae that marked the deaths of these massive stars created the first heavy elements, which we call "metals". The dark matter halos in which the stars formed were so small that they could not contain these violent supernova explosions, allowing the newly forged metals to disperse into the proto-intergalactic medium. Eventually, these metals would mix into cold, dense gas to form the next generation of stars. These would be the first able to survive to the present day, and indeed can be found scattered through the outskirts of our own Milky Way, the remnants of galactic pre-history.
In this PhD project, the student will explore the origins of the first metal-enriched stars using cutting-edge high-resolution cosmological simulations. These simulations follow the formation of the first stars, their supernovae, and subsequent dispersal of metals into the large-scale structure as the age of galaxy formation begins. There are numerous questions that can be pursued in this project. What was the influence of the first generation of stars? How were metals first incorporated into cosmic structures? How and when did dust grains (crucial to star formation today) initially form? What are the observable signatures of this epoch? This computationally intensive project will begin by analyzing existing simulation data, but there will be the option to run new simulations or develop new codes for modeling, chemistry, and analysis. The student will have access to the IfA's computing cluster and will work in an environment with many researchers with relevant expertise in galaxy formation simulations as well as observations of high-redshift galaxies and local stellar populations.