Brian T. Cook

About

Welcome! My name is Brian Cook; I am working on my PhD in astrophysics at the University of North Carolina at Chapel Hill. You can learn more about my research interests elsewhere on this site.

I grew up in Michigan and have lived in the United States and the Netherlands exploring my professional interests in academia and industry. In my free time I enjoy reading, watching movies, the outdoors (especially in the fall), and spectator sports (Go Blue and Go Heels!). In addition to any research-related questions/feedback/advice you may have, I am also receptive to any tips for hiking and camping in the Carolinas!

Research

I briefly describe my previous research experience (and give a broad introduction to each topic) here.

N-body solvers and Star Clusters

There are a variety of ways to simulate a collection of astronomical objects bound together by gravity, and globular clusters push the boundaries of what can be done computationally. A brute-force O(N^2) approach would take many months to complete on a supercomputer due to the dramatically varying spatial and temporal scales present in the resolution of the underlying dynamics. Astrophysicists have come up with a number of clever ways to mitigate these issues; this sort of effort will be the focus of my time at Carolina.

My master's thesis at the Leiden Observatory focused on how star clusters get phase-mixed on their way to becoming tidal debris. The basis for my findings were some simulations I designed using the AMUSE environment, a sophisticated Python wrapper for existing astrophysics codes written in lower-level languages. In establishing how things like a star cluster's manifold dimension and differential entropy depend on its proximity to the galactic center, we hope to better understand the physics behind the debris being discovered with Gaia/Rubin/Roman data in the coming years.

Galactic Archaeology

Galactic archaeology is the branch of research devoted to determining the formation history of the Milky Way. Galaxies form in what is known as a hierarchical process; smaller galaxies are accreted by larger galaxies, which in turn causes the larger one to grow. As the smaller galaxy is tidally stripped, it leaves behind signatures in the form of objects like stellar streams and globular clusters.

As a summer intern at MIT Lincoln Lab, I developed a routine for identifying substructure in the Milky Way comprised of RR Lyrae variables, a popular standard candle in this context, based on hierarchical clustering. You can learn more about our results in Cook et al. (2022). I have been expanding on this effort with the new Gaia DR3 release and hope to report on my findings soon!

Large-scale Structure Simulations and the Circumgalactic Medium

It is theorized that during a period of rapid inflation after the Big Bang, small quantum fluctuations were forced onto macroscopic scales. Cosmologists can use observations of the cosmic microwave background to map these overdense anisotropies in the Universe, in addition to determining the abundances of things like baryonic matter and dark energy. With this set of initial conditions, a wide set of cosmological simulations have been developed.

These simulation suites are comprised of state-of-the-art algorithms that treat astrophysical phenomena operating on different length and time scales simultaneously. The outputs can then be analyzed to test the effects of underlying physics theories (e.g., star formation or AGN feedback) on observables.

During my first year in Leiden, I analyzed low-mass, star-forming galaxies produced by the EAGLE simulations. My first project presents an analysis of the circumgalactic medium (CGM) of these galaxies; often defined as the material gravitationally bound to the galaxy but outside of the disk, the CGM is critical to understanding galaxy formation and evolution.

Star and Planet Formation

Stars form when dense cores of molecular clouds collapse; this occurs when the self-gravitation of these cores overwhelms support mechanisms like pressure. The youngest protostars often have a disk surrounding them, and the disk/protostar pair work together to create a bipolar outflow which illuminates the surrounding envelope. This illumination, called the scattered light nebula, can be used to infer properties of the disk/protostar system. In Cook et al. (2019), we show that the scattered light nebula of L1527 IRS, a Class 0/I protostar in the neighborhood of the Taurus constellation, can be qualitatively reproduced through simulations if the disk has a pronounced warp.

It is from these disks that planets eventually emerge. I spent a semester as an undergrad at Michigan working with a set of N-body codes to explore how planets interact with the protoplanetary disk. Some planets will drift inwards after losing angular momentum from prolonged tidal interactions with the disk; this may explain why we find so many massive planets very close to their host star. (It is worth noting that this class of planets are also the easiest to detect.)

CV

Curriculum Vitae.

Contact

I can be reached by e-mail (briantcook3070 [at] gmail.com or btcook [at] unc.edu).

Links

LinkedIn, GitHub, Google Scholar.

Elements

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