2025 SURF Projects

Understanding the Impact of the Interferometric Response on Gravitational Wave Observations

Supervisor: Prof. Reed Essick

Next-generation ground-based gravitational-wave (GW) interferometers are expected to have arms as long as 40 km, an order of magnitude longer than current detectors. With such long arms, the round-trip travel time for light to circulate within the arm can become comparable to the frequency of the GW signals being observed. This leads to interesting effects within the interferometer’s response which are often neglected in models of the current detectors’ response. We will investigate the impact of these effects on the ability to distinguish between different GW polarizations at both low and high frequencies. We will also investigate whether these effects can limit the precision with which we can observe post-merger signals from binary neutron star coalescences and implications for the supra-nuclear equation of state. Finally, we will consider the implications for sensitivity to GW signals at very high frequencies.

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The Cosmic Evolution of Merging Black Holes

Supervisor: Prof. Maya Fishbach

Gravitational-wave observatories LIGO-Virgo-KAGRA have detected hundreds of binary black hole mergers. The distance to each source tells us how long ago the merger happened, and we can start to map the merging black hole population over cosmic history. For this project, the student will analyze the gravitational-wave data to learn about the binary black hole merger rate as a function of cosmic time. This will allow us to answer questions like: what are the progenitors of binary black holes? What environments did they live in? How long does it take black holes to merge? 

Plot: From Schiebelbein-Zwack & Fishbach (2024) 

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Exploring Astrophysical Transients and Their Host Environments

Supervisor: Dr. Aditya Vijaykumar, Dr. Biprateep Dey, Prof. Maya Fishbach

The Universe produces a rich variety of transient phenomena including supernovae, gamma ray bursts, fast radio bursts, and gravitational waves. Such phenomena will grow dramatically in number in the next  few years thanks to the advent of the Vera Rubin Observatory, the CHIME outrigger telescopes, and ongoing observations by LIGO-Virgo-KAGRA. This will provide a great opportunity to ask questions about the population of such sources and the environments that nurture their formation and evolution.

As a part of this project, the SURF student will develop new techniques to study the connection between transient phenomena and their host environments, and apply them to existing data wherever applicable. The student will learn about formation mechanisms of these transients, the nature of their host environments, stellar evolution, and advanced data analysis techniques. The student will be embedded in the Compact Objects research group at CITA, and will have a chance to participate in all activities of the group.

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Evaluating Probabilistic Methods for Galaxy Distance Estimation

Supervisors: Dr. Biprateep Dey

Modern astronomy heavily relies on accurate distance measurements to understand the structure and evolution of our universe. The primary method for measuring galaxy distances is through their redshift – the stretching of light waves due to cosmic expansion. While precise spectroscopic redshift measurements are ideal, obtaining these for large numbers of galaxies is time-intensive and often impractical. As an alternative, astronomers estimate redshifts using multi-band imaging data, a technique known as photometric redshift estimation.

Contemporary approaches to photometric redshift estimation have evolved from providing single-point estimates to generating full probability distributions. However, these probabilistic estimates require rigorous validation to ensure their reliability for astronomical research. This is particularly crucial as these measurements form the foundation for many astrophysical studies.

This project explores the statistical robustness of photometric redshift measurements by examining whether the probability distributions produced by different estimation methods are well-calibrated. For instance, if an algorithm predicts a 95% prediction interval for a galaxy’s redshift, does the true spectroscopic redshift actually fall within that range 95% of the time? This question is fundamental for applications ranging from mapping large-scale cosmic structures to studying galaxy evolution across cosmic time.

Students will work with real astronomical data to:

  1. Apply multiple photometric redshift estimation methods to a dataset of galaxies with known spectroscopic redshifts.
  2. Implement recent statistical tools to assess the reliability of these probability estimates.
  3. Evaluate how measurement uncertainties and biases in training samples affect these methods.

This project bridges fundamental astrophysics with modern statistical techniques, providing insights crucial for current challenges in observational cosmology and galaxy evolution studies. Applicants with a basic background in statistics and machine learning techniques will be the most suited for this project however it is not a requirement.

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Mapping the Milky Way Disk with SDSSV: where are the spiral arms?

Supervisors: Dr. Neige Frankel

Many disk galaxies are observed to have spiral arms shaped by the distribution and density of stars and gas in them. Those spiral structures are considered the drivers of galactic evolutionary processes as they shuffling the orbits of stars. While we cannot study the impact of spiral arms in far-away galaxies, we have an immediate access to star-by-star data in our own galaxy. Although hard to characterise from a close vantage point (looking from within our own galaxy we can only see a small volume of stars, some too faint, others hiding behind clouds of dust), there is sufficient evidence that the Milky Way has spiral arms as well. 

In this project, we plan to go around this problem by not looking at the stellar density, but by looking at the stellar mean abundances (or composition). Indeed, there are many reasons why stellar abundances, should be, on average, different in and around spiral arms, either as a result from dynamical processes or formation processes. This has been verified in local samples (see Hackshaw+24), we will extend this to a larger fraction area of the Milky Way disk and quantify the spiral properties. 

The student will work with the latest, state-of-the art, data from the SDSSV spectroscopic survey and from the Gaia Space Satellite. The first step will be to make sense of these observations: position on the sky, distance to stars, their surface abundance (or composition) and clean the dataset. The second step will be to do data manipulation and develop visualization techniques to mine any signal of spiral arm out of the data. Finally, the student will fit a simple spiral arm model to the dataset, to extract the abundance-spiral arm parameters (strength, angle, etc.). Finally, we will make efforts to interpret these results: what does it tell us about the spiral arms? Are those abundance spirals resulting from dynamical phenomena or from formation processes? 

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Binary Black Hole Dynamics in Disks of Active Galactic Nuclei

Supervisor: Dr. Yanlong Shi

Black hole binaries are expected to exist in disks of active galactic nuclei (AGN) and are expected to be sources of gravitational waves that may be detected by current and future detectors. The interaction between the binary and the AGN disk affects the dynamics of the system.

This project aims to model the dynamics of this kind of system with numerical simulations of magnetohydrodynamics. Unlike previous attempts, the project adds new complexities, such as more realistic magnetized disks and zoom-in techniques. The student should know the basics of hydrodynamics and Python programming and gain some additional knowledge in computational fluid dynamics and its applications in astrophysics at the end of the project.

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Exploring Black Hole Contents in Dense Star Clusters Using Limepy

Supervisor: Dr. Claire Ye and Prof. Gwendolyn Eadie

The amount of mass that black holes contribute to globular clusters has long been a mystery. Black holes play a crucial role in the dynamical evolution of globular clusters, influencing the mass distribution of stars and the cluster’s surface brightness. They also affect the evolution of other cluster objects, such as neutron stars, thereby impacting the formation of multi-messenger phenomena like gravitational wave sources and millisecond pulsars. Therefore, probing the black hole content in globular clusters has broad applications in astrophysics. Due to their dark nature, detecting black holes in globular clusters through direct observations is challenging. Instead, black hole masses in clusters can be inferred indirectly from cluster properties, such as total cluster mass, core radius, and half-mass radius. We propose to study black hole masses in globular clusters using limepy models, which estimate cluster mass and half-mass radius based on the distribution functions of stars. By comparing model masses from limepy to N-body simulated or observed cluster masses, we can estimate the black hole mass ratios in clusters. For this study, we will utilize cluster position and velocity data from realistic N-body cluster simulations or Gaia observations.

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Unraveling the Radiative Properties of the Interstellar Medium

Supervisor: Dr. Ioana Zelko

A comprehensive 3D map of the properties of dust can serve as a great probe for the interstellar medium (ISM), as well as the radiation field of the galaxy, which plays a critical role in many applications, including physics of the galactic magnetic fields, polarization measurements, modeling of the diffuse Galactic gamma-ray emission, and star formation.

Previous work(1)has combined existing 3D maps of the reddening (-> density) of the dust in the ISM, with emission observed by Planck and IRAS at five frequency bands, to create a 3D temperature map2 of the interstellar dust temperature, at resolutions of 27’ (see figure below).

In this project, the student can build on the 3D dust temperature map to explore potential applications: correlations with star forming regions with other data catalogs, interstellar radiation field calculation, dark matter, magnetic fields, as well as other ideas. Resolution matching will likely play a role in determining the feasibility of the application.

The student will gain knowledge of theory, data analysis, statistics and programming, with the possibility of practicing oral, visual, and written science communication and publication. Project details can change to match the students skills and interests.

1 https://arxiv.org/pdf/2211.07667.pdf
2 https://www.youtube.com/playlist?list=PLijDPBNhGIqQccgN0BKJciE16NJ1PtsdO

Figure description: 3D visualizations of the 27′ resolution map of the temperature of galactic dust and its density. Perspective shown in the galactic plane towards the anti-center (180◦ galactic longitude), towards the Orion, Taurus, Perseus, and California clouds. Credit: Zelko et al. 2022.

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