Research  Classes  Lectures &      Events  People For Students For Faculty Search &     Site Map Physics Home ON THIS PAGE: John E. Carlstrom | Juan I. Collar | Corbin E. Covault | James W. Cronin | Roger H. Hildebrand | Stephan Meyer | Dietrich M�ller | Simon P. Swordy | Bruce D. Winstein Experimental Astrophysics The University of Chicago is a major center for interdisciplinary research in experimental astrophysics and cosmology. Members of the Department of Physics work in close collaboration with members of the the Department of Astronomy and Astrophysics. Research in experimental astrophysics is organized under the Enrico Fermi Institute. Groups that are involved in experimental astrophysics research include members of the Laboratory for Space Research (LASR) and the High Energy Physics group. Members of the department are active in several different areas including Studies of the cosmic microwave background radiation spectrum and anisotropy, Cosmic dust studies detect polarization in the far-infrared emission as a probe of magnetic field structure, Investigations of solar, magnetospheric, and heliospheric phenomena, High energy gamma-ray astrophysics, Studies of high energy emission from active galaxies, supernovae, and pulsars, and Studies of the origin of cosmic rays from the lowest to the highest possible energies. Experimental programs are developing new detectors for space-based experiments, balloon payloads, and ground based systems. Roger H. Hildebrand Ph.D., California, Berkeley, 1951. Samuel K. Allison Distinguished Service Professor Emeritus, Dept. of Physics, Dept. of Astronomy & Astrophysics, Enrico Fermi Institute. Experimental physics, infrared astronomy. Hildebrand and his students study interstellar magnetic fields by mean of far-infrared polarimetry. This technique has made it possible to observe field configurations associated with filamentary clouds, rotating clouds, collapsing clouds, shock fronts, and other interstellar environments. It has also made it possible determine the ratio of uniform to turbulent components of the field and to show that this ratio remains approximately constant from dense molecular clouds to the diffuse interstellar medium. Observations with the University of Chicago polarimeter, Hertz, at the Caltech Submillimeter Observatory have led to a wholly unexpected discovery. Comparison of results at 350 �m with earlier results at 60 �m and 100 �m from the U. of C. polarimeter, Stokes, on the Kuiper Airborne Observatory and with recent results from the James Clerk Maxwell Observatory have shown that the degree of polarization depends strongly on the wavelength. From these results we infer that the cloud medium must be heterogeneous. There must be domains at different temperatures with dust grains of different polarizing power. The results on the polarization spectrum and on field configurations are providing a basis for estimating the interference of Galactic dust emission on measurements of the polarized component of the cosmic microwave background. To extend these investigations, Hildebrand and his students are working on the design of a polarimeter for NASA's new airborne Stratospheric Observatory for Infrared Astronomy (SOFIA). Submillimeter Array Polarimetry with Hertz. C.D. Dowell, R.H. Hildebrand, D.A. Schleuning, J.L. Dotson, G. Novak, T. Renbarger, M. Houde. Ap. J. 504, 588, 1998. The Far-Infrared Polarization Spectrum: First Results and Analysis. R.H. Hildebrand, J.L. Dotson, C.D. Dowell, D.A. Schleuning, J.E. Vaillancourt. Ap. J. 516, 834, 1999. Summary of Results from Far-Infrared Polarimetry. J.L. Dotson, C.D. Dowell, D.A.Schleuning, R.H. Hildebrand. Ap.J.S. 128, 335, 2000. Submillimeter Polarimetric Observations of the Galactic Center. G. Novak, J.L. Dotson, C.D. Dowell, R. H.Hildebrand, T. Renbarger, D.A. Schleuning. Ap. J. 529, 241, 2000. A Primer on Far-Infrared Polarimetry. R.H. Hildebrand, J.A. Davidson, J.L.Dotson, C.D. Dowell, G. Novak, and J.E. Vaillancourt. Submitted to PASP (2000). Interstellar Magnetic Fields and Infrared-Submillimeter Polarimetry. R.H. Hildebrand. In Astrophysical Spectropolarimetry, ed. J. Trujillo, Cambridge University Press, 2001. updated 4/2001