Title: Exploring the explosion mechanism of core collapse supernovae

Supervisor: Almog Yalinewich

When massive stars exhaust their nuclear fuel, they explode and give rise to a spectacular transient called a supernova. However, the explosion mechanism is not fully understood, and in particular how the shock wave is able to overcome gravity and sweep across the star. The successful candidate will tackle this problem using a combination of mathematical models and state of the art computer simulations, and thus gain research experience and develop skills in high performance computing. Preference will be given to candidates with prior experience with the python and C++ programming languages, as well as prior knowledge of stellar structure and evolution and fluid dynamics.

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Title: Multiple lines of enquiry at high redshift: simulating line-intensity mapping analyses

Supervisor: Dongwoo Chung

Line-intensity mapping (LIM) surveys in the next decade will produce observations of fluctuations in integrated line intensity across large cosmological volumes, targeting various radio and sub-millimetre lines that all trace matter and galaxies in different ways. Maximising the science value of LIM surveys will require leveraging certain analysis techniques, like cross-correlations between (or even within) surveys that will allow inference of more information with more confidence compared to analysing only auto-correlations for each target line. However, forecasting such analyses requires self-consistent, physically motivated line-emission models that can be applied to large cosmological simulations. The project will build on existing simulation frameworks to simulate LIM signals and observations, with an eye on science goals of near- and far-future surveys. The student will gain skills related to analysis of numerical simulations, as well as understanding of high-redshift astrophysics and cosmology. Given the wide range of possibilities, details will change to match the student’s exact interests.

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Title: Strongly lensed galaxies in the FIRE cosmological simulations

Supervisors: Omar Contigiani and Lichen Liang

In Einstein’s General Relativity, the presence of a massive object along the line of sight distorts the light emitted by background sources. This effect is known as gravitational lensing, and it represents one of the most striking predictions of this theory. Its most famous application is the fact that distant galaxies are magnified by nearby ones, resulting in brighter, but distorted images. In particular, this distortion depends heavily on the relative lens-source position in the sky. This leads to differential lensing: if the components of a galaxy have different spatial distributions, then their magnifications will be different.

The goal of the project is to investigate the effects of differential lensing on two such components, the thermal emission of dust and the collisional excitation lines emitted by interstellar gas. The study will adopt a sample of high redshift galaxies from the latest FIRE cosmological simulations. The student will produce the mock observations for these galaxies in multiple broadband filters, run gravitational lensing software to reproduce the lensed images, and then compute the lensing magnification of the two components.

The project will be co-led by two postdocs at CITA. Dr. Contigiani is an expert in gravitational lensing, and Dr. Liang is an expert in galaxy evolution theory who will provide the data products from FIRE simulations. We are looking for students interested in gravitational lensing, scientific computing, and data visualization techniques. They will gain experience and knowledge in diverse research areas: cosmology, structure formation, galaxy evolution, and scientific programming. Depending on the quality of the final results, this work might lead to a peer-reviewed publication. The project idea is novel, and we expect the student to have loads of fun!

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Title: Probing the first billion years of the Universe’s history

Supervisor: Jennifer Chan

The Universe is not the same today as it was yesterday. It is now structured as a giant cosmic web, where galaxies are embedded and the intergalactic space is filled with ionised gas. However, it was once generally smooth and filled with neutral gas, which is predominantly hydrogen. The Universe must have undergone a major transition that transformed it from being structureless to structure-filled, and from being neutral to being almost completely ionised. This major transition concerns the first billion years of cosmic history. It is referred to as cosmological reionisation and forms a few key science projects of current and upcoming radio telescopes (e.g. HERA and SKA). In this project, student will learn how to probe the Universe’s first structure formation period and the reionisation epoch using the 21-cm line of neutral hydrogen. They will gain hands-on research experience simulating ionised bubbles and solving radiative transfer equation, hence, making theoretical predictions of the reionisation imprints on the redshifted 21-line radiation that we would observe today.

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Title: How do disk galaxies warp?

Supervisors: Ted Mackereth, Josh Speagle, Neige Frankel

Many disk galaxies, including our own Milky Way, are observed to be “warped” in the outer regions of their disks (i.e. S-shaped compared to their geometrical midplane) when looking at their stars and gas. An example of such a galaxy in the cosmological simulation TNG50 is in the picture attached, which shows a face-on and side-on view of the mass distribution of the stars and the gas at four different times. The origin, lifetime and dynamical nature of these warps, however, are not well understood. Current hypotheses range from, for example: tidal torques exerted by satellite galaxies, misaligned dark matter halos, or accretion from gas in the galactic outskirts.

In this project, the student will explore the processes that drive such disk deformations, by analyzing outputs from Illustris TNG50, a state-of-the art magneto-hydrodynamical cosmological simulation that computes the formation and evolution of hundreds of thousands of galaxies. In particular, they will investigate:

1. What causes warp formation?
2. How do warps evolve, and what are their lifetimes?
3. What happens to stars born in warps?

This project will involve working with large databases and some amount of coding, and may also involve some statistics and theory depending on student interests. The student will integrate the daily life at the research institute and be invited to participate in CITA’s events, such as regular meetings with supervisors, regular group meetings, seminars, etc., thereby being exposed to the full and exciting research experience!

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Title: Observing neutron stars with gravitational waves

Supervisor: Philippe Landry

Neutron star mergers are rich sources of astrophysical information, telling us about the structure of ultra-dense matter, the origin of the universe’s heavy elements, and the engine for short gamma-ray bursts. To interpret the gravitational waves emitted by these mergers, we rely on theoretical models for neutron stars. By comparing these models’ predictions to gravitational-wave data, students will help refine our understanding of neutron star matter and populations. In the process, students will learn about stellar structure and strong gravity, and develop skills in data analysis, Bayesian statistics and Python programming.