James Lombardi
Allegheny College

Background Information

My research students and I work in computational astrophysics. We use Smoothed Particle Hydrodynamics (SPH) calculations to study stellar interactions, and, in particular, stellar collisions and mergers. One environment where stellar interactions occur frequently is a so-called globular cluster. Globular clusters are collections of many hundreds of thousands of stars found in galactic halos, the sparse region outside of the disk of a galaxy, and are thought to have formed early in the evolution of the universe.

One exciting aspect of dense stellar systems such as globular clusters is the simultaneous importance of three principal areas of stellar astrophysics: dynamics, evolution, and hydrodynamics. Many simulation codes focus on one of these areas and have often been lifelong works in progress. The first attempts at unifying these treatments into a coherent model to describe clusters have begun only relatively recently (see the MODEST home page). Attempting to integrate stellar dynamics, evolution, and hydrodynamics codes into one fully functional package will be challenging, largely because each area treats stellar properties that evolve on different time-scales. However, by combining these areas, we will be able to better model the origins, dynamics, evolution, and death of globular clusters, galactic nuclei, and other dense stellar systems.

At Allegheny, our focus is on modelling hydrodynamic interactions between stars. There are many types of exotic stellar objects that may be formed from stellar mergers and collisions, including blue stragglers, binary neutron stars, ultracompact X-ray binaries, catacylsmic variables, helium stars, and rapidly rotating horizontal branch stars. One of our goals is to develop a software module for quickly generating collision product models, ultimately for any type of stellar collision, that could be incorporated into simulations of dense star clusters.

Learn More

Last updated: July 2009