Department of Physics, Engineering Physics & Astronomy

Department of Physics, Engineering Physics & Astronomy
Department of Physics, Engineering Physics & Astronomy
Professor  Emeritus Richard Henriksen

Richard Henriksen

Professor Emeritus
Emeriti
Office:
Stirling 511B
Phone:
613-533-6000 ext. 36851
About:

Degree:

PhD (Manchester)

Research Interests:

My interests have ranged widely over the field of astrophysics. At present a major theme is the attempt to construct a detailed model of the birth of stars. We should remember that the stars provide the light and heat of our Universe and as such are probably its dominant characteristic. We know that star birth occurs mainly in the cold molecular clouds of galaxies, but we do not understand fully the processes that lead to intense beams of matter that are ejected in diametrically opposed directions as the star forms and proceeds through its early evolution. Nor do we understand the way in which the enormous magnetic flux and angular momentum associated with the diffuse material that eventually forms the star is reduced to values compatible with the existence of the star. It is likely however that this reduction is what is happening when the beams are formed in conjunction with the giant X-ray flares that also seem to be associated with the birth of young stars. Currently I would like a graduate student to help me explore the evolution of molecular clouds towards `star-birth' by studying the nature of what might be called `Ballistic Turbulence'. Fluid turbulence is thought to decay too quickly to support the cloud over its lifetime, but a structure made up of tidally interacting clouds in an n-body structure might be better. Another dominant theme is the study of the relaxation of Dark Matter halos around galaxies and clusters of galaxies. This material can only be detected indirectly through its gravitational effects, but it consistently appears as the most massive component of the Universe. Thus the distribution in phase space of the constituent particles is important for the understanding of the dynamics of the visible `normal' matter. These systems are also intriguing theoretical systems since the dark matter particles seem to be collisionless, and so they form an n-body system of the simplest kind. We can therefore hope to use a combination of theoretical analysis and numerical simulation to study the relaxation of such systems and find perhaps a universal distribution in energy space. Existing results have been published and I hope to extend the previous researches to include angular momentum, non-spherical symmetry and a novel method of coarse graining. With a Ph D student I would like to explore the relativistic n-body problem using the same techniques. This is a particularly pure problem in general relativity since the equation of state of the matter is almost as elegant as the geometrical representation of gravity! But we also hope to make a contribution to the understanding of near `black hole' evolution. This problem involves both analytical and numerical work. In addition I continue my traditional interests in relativistic astrophysics. Pulsars remain as a puzzling physical problem and Higgins and I (see II below) have made some of the few predictions of gamma ray activity. I continue to be intrigued by the magnetic interactions between central `objects' and the surrounding disc/halo material generally. These include phenomena ranging from protostars to Quasars. Student interest is welcomed.

Selected References

Henriksen, R.N. 2006, "Power-laws and non-Power-laws in Dark Matter Halos", Astrophysical Journal, 653, Dec. 20. MacMillan, J.D., Widrow, L.M. \& Henriksen, R.N., 2006, "On Universal Halos and the Radial Orbit Instability", Astrophysical Journal, 653, Dec. 10. Henriksen, R.N. 2005, " Isolated and non-isolated dark matter halos and the NFW profile", Mon. Not. R. astron. Soc. 366, 697. Henriksen, R.N. 2004, "Coarse graining the distribution function of cold dark matter-II", Mon. Not. R. Astron. Soc. 355, 1217=1236. Le Delliou, M. and Henriksen R.N. 2003, "Non-radial Motion and the NFW Profile", Astronomy and Astrophysics, 408, 27-38. Merrall T.E.C. and Henriksen R.N. 2003, "Relaxation of a Collisionless System and the Transition to a new Equilibrium", Astrophysical Journal, 595, 43-58. Lery T. Henriksen R.N., Fiege J.D., Ray T.P., Frank A., Bacciotti F. 2002, "A Global Jet/Circulation Model for Young Stars", Astronomy and Astrophysics, 387, 187 Henriksen R.N. and LeDelliou M. 2002, "Coarse Graining the Distribution Function of Cold Dark Matter", Mon. Not. R. Astron. Soc, 331, 423-434. MacMillan J.D. and Henriksen R.N. 2002, "Black Hole Growth in Dark Matter and the Mbh-Sigma Relation", ApJ, 569, 83. Aburihan Mahmoud, Fiege J.D., Henriksen, R.N. and Lery, T. 2001, "Protostellar Evolution during Time Dependent, Anisotropic Collapse", Mon. Not. R. Astron. Soc., 326, 1217-1227. Lery T., Henriksen R. N. and Fiege J.D. 1999, "Magnetized Protostellar Bipolar Outflows", A&A 350, 254. Henriksen, R.N. and Widrow, L.M. 1999, "Relaxing and Virializing a Dark Matter Halo", Mon. Not. R. Astron. Soc. 302, 321. Higgins M.G. and Henriksen R.N. 1997, "The Deutsch field gamma-ray pulsar-I. The model basics", Mon. Not. R. Astron. Soc. 292,934. Higgins M. G. and Henriksen R.N. 1998,"The Deutsch field gamma-ray pulsar-II. Application of the model", Mon. Not. R. Astron. Soc 295, 188. Henriksen R.N. 1997, "Multi-dimensional self-similarity, and self-gravitating N body systems", in "Scale Invariance and Beyond", Dubrulle,Graner and Sornette,eds, Springer, EDP Sciences.