Shedding light on dark matter: Probing the cusp/core problem with the Milky Way's tidal streams

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Dark matter is invisible, but its presence is detected via its gravitational effect on stars and galaxies. One powerful way to study dark matter is by looking at “tidal streams” that originate from globular clusters. These are long, thin trails of stars that are pulled away from dense clusters of old stars as they orbit the Milky Way. Tidal streams of stars can have a variety of shapes and thicknesses, and they can also have distortions in their shapes, such as “gaps”, “spurs”, or “cocoons”. These distortions contain information about the distribution of dark matter in the original dwarf galaxy where the globular clusters first formed, before the dwarf galaxy merged into the Milky Way. In this project, a team from the University of Michigan, Ann Arbor, will run a suite of computational simulations to understand how the underlying dark matter distribution affects the observed properties of globular cluster streams. The team will then use data from the Dark Energy Spectroscopic Instrument (DESI) survey to study the properties of Milky Way. As part of this project, the team will also support K-12 education by running a summer camp for high school students, where the students will learn about the forefront of astronomy and work with real astronomical data. Intriguingly, the detailed physical and velocity structure of globular cluster streams depends on the central dark matter density profile in the original dwarf galaxy in which the globular cluster was born. The goal of this project is to take advantage of this discovery by using a new spectroscopically selected sample of globular cluster tidal streams to probe the cusp/core problem in dwarf galaxies. The research team will combine advanced simulations, simulation-based inference and optimal experimental design and new observational data to explore this issue. The suite of N-body simulations to model how globular cluster streams form and evolve in different dark matter environments will be examined to determine quantitative metrics of stream “heating” and structure. These metrics will be compared with those measured for real tidal streams using new stellar velocity and chemical data from DESI. This comparison will help to constrain the dark matter density profiles of the original host galaxies of these globular clusters. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.