Jeremy Webb

Postdoctoral Fellow

University of Toronto





Globular clusters are spherical collections of between 106 and 107 stars that are found in all types of galaxies. The globular cluster M80 (Image Credit: is an example of just one of the over 150 globular clusters found in our own Milky Way. My research focuses on studying the dynamical evolution of globular clusters from birth to present day. More specifically, I am interested in the relationship between a globular cluster and the gravitational field of its host galaxy. What role does the host galaxy play in a cluster's evolution? Is the cluster's location and orbit within a galaxy a contributing factor?

I enjoy taking both a theoretical and observational approach to studying globular clusters. My observational work has involved taking new and archived Hubble Space Telescope images of the giant elliptical galaxy M87 and studying its extensive globular cluster population. In the image to right, we have subtracted the excess brightness of the M87 galaxy to reveal both the inner globular cluster population and the famous M87 jet. I search for trends in various globular cluster properties with galactocentric distance that would indicate the gravitational field of M87 has affected the dynamical evolution of its cluster population.

My theoretical work makes use of the N-body code NBODY6 devloped by Sverre Aarseth. NBODY6 can generate a population of stars (each with its own position, velocity, mass, metallicity, etc.) and calculate both the motion and stellar evolution of each star as a function of time. Hence it is possible to take a newly formed globular cluster, let it evolve for 12 Gyr, and determine what it would look like if observed today. In the image to the left, we have plotted the position of each simulated star after 12 Gyr of evolution. Red data points mark stars that are gravitationally bound together while black data points mark stars that have escaped the cluster and now populate its tidal tails. Since NBODY6 can also include the gravitational field of a host galaxy in its calculations, my theoretical work has involved simulating model clusters in a Milky Way-like potential to determine the effects that orbital distance, eccentricity, and inclination can have on the dynamical evolution of globular clusters.