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Physics & Astronomy

Dan Homan Affiliation Faculty Title Assistant Professor Email homand@denison.edu Phone 740-587-6742 B.S. in Physics from University of Maine, 1994 M.A. in Physics from Brandeis University, 1996 Ph.D. in Physics from Brandeis University, 1999 View my personal page

One of the things that excites me most about Physics is our continuing struggle to develop a better understanding of how the world works at a fundamental level.  We Physicists also work to apply that understanding to complex, real world problems.  For me, one of the great pleasures of Physics is finding creative ways to address these challenges.  

Teaching at Denison

I teach a variety of courses across our curriculum.  Some recent classes include...

Research

I study distant active galaxies. Active galaxies are extremely energetic galaxies, giving off so much energy that they can be viewed from billions of light years away. Sometimes only the center of the galaxy is visible at such great distances, giving it a star-like, or 'quasi-stellar', appearance in our sky.  This is the origin of the name 'quasar' which is used to describe some of these very far away, very bright galaxies.

All of the unusual, energetic behavior in an active galaxy can ultimately be traced to its galactic center or nucleus, a region only a few light years across.  These objects are therefore often called "Active Galactic Nuclei" or "AGN" for short. AGN come in a variety of types, displaying a wide range of characteristics including broad spectral lines, large variability in their apparent brightness, and possibly jets of plasma streaming from their center.  Despite their apparent differences, it is now believed that all of these objects have, at their center, a super-massive black hole (Millions or even Billions of times the mass of our Sun) and associated accretion disk that are responsible for all the energetic phenomena that we observe.

There is a sub-class of AGN that have strong jets of plasma which stream outward from the galactic nucleus and are visible at radio wavelengths. These radio jets come in a number of morphologies with the most spectacular maintaining collimated flows for tens or even hundreds of thousands of parsecs (1 parsec is about 3.3 light-years) before terminating at hotspots in large, inflated radio lobes.  I study these jets to understand their physical properties and how they are created by the super-massive black hole and accretion disk at the center of the galaxy.

For more information, contact walter@denison.edu.
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