Dr. Dan Homan Affiliation: Faculty Title: Associate 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 Dr. Dan's 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

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.

Selected Recent Journal Articles

Lister, M. L., Homan, D. C., Kadler, M., Kellermann, K. I., Kovalev, Y. Y.; Ros, E., Savolainen, T., & Zensus, J. A. 2009. "A Connection Between Apparent VLBA Jet Speeds and Initial Active Galactic Nucleus Detections Made by the Fermi Gamma-Ray Observatory".  The Astrophysical Journal, Letters. v. 696 p. L22

Homan, D. C.,  Lister, M. L.,  Aller, H. D.,  Aller, M. F., & Wardle, J. F. C., 2009.  "Full Polarization Spectra of 3C279".  The Astrophysical Journal.  v. 696 p. 328

Kadler, M., Ros, E., Perucho, M., Kovalev, Y. Y., Homan, D. C., Agudo, I., Kellermann, K. I., Aller, M. F., Aller, H. D., Lister, M. L., & Zensus, J. A., 2008. "The Trails of Superluminal Jet Components in 3C111".  The Astrophysical Journal.  v. 680 p. 867

Y. Y. Kovalev, M. L. Lister, D. C. Homan, & K. I. Kellermann, 2007. "The Inner Jet of the Radio Galaxy M87". The Astrophysical Journal, Letters. v. 668 p. L27

M. H. Cohen, M. L. Lister, D. C. Homan, M. Kadler, K. I. Kellermann, Y. Y. Kovalev, & R. C., 2006. "Relativistic Beaming and the Intrinsic Properties of Extragalactic Radio Jets." The Astrophysical Journal. v. 658 p. 232

D. C. Homan, Y. Y. Kovalev, M. L. Lister, E. Ros, K. I. Kellermann, M. H. Cohen, R. C. Vermeulen, J. A. Zensus, & M. Kadler, 2006. "Intrinsic Brightness Temperatures of AGN Jets." The Astrophysical Journal, Letters. v. 642 p. L115

D. C. Homan & M. L. Lister, 2006. "MOJAVE: Monitoring of Jets in AGN with VLBA Experiments - II. First Epoch 15 GHz Circular Polarization Images." The Astronomical Journal. v. 131 p. 1262

Click Here for a Full Listing of Peer Reviewed Journal Articles

Selected Recent Conference Presentations

D. C. Homan, M. L. Lister, H. D. Aller, M. F. Aller, & J. F. C. Wardle, 2009. Talk: "The Magnetic Field Structure and Particle Population of the Parsec-Scale Jet of 3C279".  American Astronomical Society Meeting 213, BAAS #342.06 

M. McCormick*, D. C. Homan, M. L. Lister, & Y. Y. Kovalev, 2009. Poster: "Probing the Intrinsic Brightness Temperature Distribution of the MOJAVE Complete Sample".  American Astronomical Society Meeting 213, BAAS #446.09

C. Baldwin* & D. C. Homan, 2009. Poster: "Circular Polarization from Helical Fields in Extragalactic Radio Jets".  American Astronomical Society Meeting 213, BAAS #422.10

D. C. Homan, 2007. Invited Talk: "Studying the Physics of AGN Jets Near Their Origin". Division of Plasma Physics Meeting in Orlando, FL, Nov. 12-16.

Nichloas Geitner* and Daniel Homan, 2007. Poster: "The Dynamics of Extragalactic Jets". Ohio Section of the APS Fall Meeting at Miami University, Oct. 19-20 .

Brian Welch* and Daniel Homan, 2007. Poster: "Simulations of Polarization from Radio Jet Cores of Active Galactic Nuclei". Ohio Section of the APS Spring Meeting at Eastern Michigan University, May 4-5.

D. C. Homan, 2007. Invited Review: "VLBI Observations of Blazars (and other AGN) pre and post-EGRET". VLBI in the GLAST Era at NASAs Goddard Space Flight Center.

* Denotes Denison Undergraduate

Research Grants to Support This Work

"RUI:  Probing the Physics of Extragalactic Jets on Parsec Scales" by D. C. Homan.  Funded by the National Science Foundation's Extragalactic Astronomy and Cosmology program for $97,806.00 from 2007-2010

"Investigating the Circular Polarization of Extragalactic Radio Jets" by D. C. Homan.  Funded by Research Corporation for $23,700 from 2005-2007