Faculty Research Summaries | Chairman's Introduction

• John E. Carlstrom, Professor, Department of Astronomy and Astrophysics , Enrico Fermi Institute, and the College; Director, Center for Astrophysical Research in Antarctica
• James W. Cronin, Professor, Departments of Astronomy and Astrophysics, and Physics, Enrico Fermi Institute, and the College
• Kyle M. Cudworth, Associate Professor, Department of Astronomy and Astrophysics; Assistant Chairman for Academic Affairs, Department of Astronomy and Astrophysics
• Scott Dodelson, Assistant Professor, Department of Astronomy and Astrophysics and the College
• Joshua A. Frieman, Associate Professor, Department of Astronomy and Astrophysics; Head, Theoretical Astrophysics Group, Fermi National Accelerator Laboratory
• Doyal A. Harper, Jr., Professor, Department of Astronomy and Astrophysics and the College
• Roger H. Hildebrand, Samuel K. Allison Distinguished Service Professor Emeritus, Departments of Physics and Astronomy and Astrophysics, Enrico Fermi Institute, and the College
• Lewis M. Hobbs, Professor, Department of Astronomy and Astrophysics and the College
• Wayne Hu, Assistant Professor, Department of Astronomy and Astrophysics, Enrico Fermi Institute, and the College
• Stephen M. Kent, Associate Professor, Department of Astronomy and Astrophysics, and the College; Head, Experimental Astrophysics Group, Fermi National Accelerator Laboratory
• Edward J. Kibblewhite, Professor, Department of Astronomy and Astrophysics, Enrico Fermi Institute, and the College
• Edward W. Kolb, Professor, Department of Astronomy and Astrophysics, Enrico Fermi Institute, and the College
• Arieh Königl, Professor, Department of Astronomy and Astrophysics and Enrico Fermi Institute
• Richard G. Kron, Professor, Department of Astronomy and Astrophysics and the College; Director, Yerkes Observatory
• Don Q. Lamb, Jr., Professor, Department of Astronomy and Astrophysics, Enrico Fermi Institute, and the College
• Stephan Meyer, Professor, Departments of Astronomy and Astrophysics, and Physics, Enrico Fermi Institute, and the College; Associate Director, Center for Astrophysical Research in Antarctica
• Richard H. Miller, Associate Professor, Emeritus Department of Astronomy and Astrophysics
• Takeshi Oka, Robert A. Millikan Distinguished Service Professor, Departments of Chemistry, and Astronomy and Astrophysics, Enrico Fermi Institute, and the College
• Angela Olinto, Assistant Professor, Department of Astronomy and Astrophysics, Enrico Fermi Institute, and the College
• Patrick E. Palmer, Professor, Department of Astronomy and Astrophysics and the College
• Robert Rosner, William E. Wrather Distinguished Service Professor, Department of Astronomy and Astrophysics, Enrico Fermi Institute, and the College
• Noel M. Swerdlow, Professor, Departments of Astronomy and Astrophysics, and History, Committee on the Conceptual Foundations of Science, and the College
• James W. Truran, Professor, Department of Astronomy and Astrophysics, Enrico Fermi Institute, and the College
• Michael S. Turner, Bruce V. Rauner Distinguished Service Professor, Departments of Astronomy and Astrophysics, and Physics, Enrico Fermi Institute, and the College, Chairman Department of Astronomy & Astrophysics
• Peter O. Vandervoort, Professor, Department of Astronomy and Astrophysics and the College
• Donald G. York, Horace B. Horton Professor of Astronomy and Astrophysics, Department of Astronomy and Astrophysics, Enrico Fermi Institute, and the College

John E. Carlstrom

Observational cosmology using new instruments to measure the primary anisotropy in the Cosmic Microwave Background (CMB) radiation and the Sunyaev-Zel'dovich Effect. Leader of the Degree Angular Scale Interferometer (DASI) project. DASI, a unique 13 element compact interferometric array located at the NSF Amundsen-Scott South Pole station, recently reported detection of the harmonic peaks in the CMB angular power spectrum. The new DASI data was used to set tight constraints on cosmological parameters, such as the curvature of the universe (1.04 +/- 0.06) and the fractional amounts of baryonic and cold dark matter. The results provide further support for Inflationary models for the origin of the universe. Current DASI observations are directed toward measuring the polarization of the CMB anisotropy.

Interferometric techniques are also used for detailed imaging of the CMB that has been scattered by hot gas associated with clusters of galaxies, the Sunyaev Zel'dovich effect (SZE). The intensity of the SZE for a cluster is independent of its distance making the SZE an ideal cosmological probe. Combining SZE measurements with x-ray observations allows an independent determination of the expansion history of the universe, as well as detailed information about these extremely large structures. A major expansion of this project, which includes building a dedicated six-element array of telescopes, has recently been funded. The factor of 100 increase in imaging speed provided by the new array will enable a SZE survey of the high redshift universe over a region of roughly 12 square degrees.

See http://astro.uchicago.edu/dasi/
See http://astro.uchicago.edu/sze/

James W. Cronin (See Department of Physics)

Kyle M. Cudworth

Studies of star clusters are fundamental to several areas of modern astrophysics: stellar evolution, Galactic structure and evolution, stellar dynamics, and the calibration of the astronomical distance scale. We are using astrometric and photometric observations to obtain high precision, clean, color-magnitude diagrams for stars in globular clusters, old open clusters, and some nearby galaxies. In several cases, stellar dynamics within a cluster can be explored in detail. Distances to globular clusters are being obtained via a new method totally independent of previous techniques. Tangential velocities of the most distant clusters associated with our Galaxy are being measured to better determine the mass of the Galaxy.

Scott Dodelson

I am interested in cosmology, in particular in the broad question of how structure formed in the universe. This question is rich not only because it is fascinating in of itself, and not only because there is much data being taken that sheds light on it, but also because it touches so many issues in astrophysics and particle physics. How do galaxies form? Is there dark, non-baryonic matter? What is it? Will the universe continue to expand forever? Did the universe expand exponentially at some early phase in its history? If so, what is the particle physics responsible for this period of inflationary expansion? These are all remarkable questions; even more remarkable is the very real hope that we will be able to answer them in the coming decade.

I believe there are three ways theoretical cosmologists can help answer these and other questions in the general field of structure formation. First, we can introduce new theories or models of how structure formed. This is especially important at present since one general model -- cold dark matter and its variants -- so dominates the theoretical landscape. Second, we can calculate the predictions of existing theories. Finally, we can analyze the plethora of data that is coming in and will be coming in over the next decade. I am interested in all three of these areas, find them stimulating, and hope to work in all of them in the coming years.

Joshua A. Frieman

Frieman's primary research is in cosmology, especially the formation of large-scale structure and the interplay between cosmology, particle physics, and astrophysics. Current research interests include the analysis of large-scale structure in galaxy surveys such as the Sloan Digital Sky Survey, and the use of weak gravitational lensing observations to probe the distribution of mass on large scales. Frieman is Head of the Theoretical Astrophysics group at Fermilab, which has close connections with the cosmologists and theoretical astrophysicists at Chicago.

Doyal A. Harper, Jr.

My research group uses infrared and submillimeter techniques to study processes related to the formation and evolution of stars, planetary systems, and galaxies. Work in progress includes observations of proto-planetary disks around main-sequence stars like Vega and Beta Pictoris; studies of cold, compact, protostellar objects in the cores of dense interstellar clouds; and observations of galaxies in which intense bursts of star formation result in infrared luminosities many times greater than their luminosities in the visible regions of the spectrum.

Roger H. Hildebrand (See Department of Physics)

L. M. Hobbs

Spectroscopic observations of the light elements lithium, beryllium, and boron in Galactic stars of all ages are being used to investigate the cosmic origin of these elements, both in the Big Bang and, in most cases, in processes that occurred much later in our Galaxy. The inferred abundances of these elements, including the two isotopic forms of lithium, pose fascinating questions about the early Universe, the chemical evolution of the Galaxy, and stellar structure. In particular, the lithium data are vitally important in empirically evaluating the properties of the Universe at a few minutes after the Big Bang.

The Hubble Space Telescope is being used to study the spectrum of the very nearby star Beta Pictoris. Strong absorption is found by gas orbiting in a solar-system-sized disk that surrounds this relatively young star; small dust particles also were previously discovered in the disk by other investigators. The time-varying gaseous absorption and the organization of the dust suggest that the disk may harbor a large number of comet-like bodies, and possibly several planets. Our current efforts are focused on detecting the faint spectral-line emission from the disk, which originates in scattering of the starlight from the parent star by the gaseous disk

In a separate program, the Hubble Space Telescope is being used to determine the spatial distribution, motions, and physical properties of individual clouds of tenuous interstellar gas in the general neighborhood of the Sun. Included are a few clouds moving toward the Sun at high speeds that apparently were ejected in relatively recent supernova explosions. The combination of the HST and its high-resolution spectrograph, augmented by ground-based observations obtained at still higher spectral resolution, allows unprecedentedly precise and detailed studies of this kind.

Wayne Hu

I am a cosmological theorist and phenomenologist.

My main interests center around the formation of structure in the universe and its relation to the dark side of the universe: namely the dark matter and dark energy that seems to pervade space.

We are fortunate to be in a time when the data that can help answer these fundamental questions is literally flooding in. I have devoted much of my recent research to two such sources: the Cosmic Microwave Background and the weak gravitational lensing of faint galaxies. The tools needed to understand these data sets encompass both analytical and numerical elements. The former involves relativistic perturbation theory, simple radiative transfer and fluid dynamics. The latter includes cosmological simulations and data analysis.

Stephen M. Kent

Stephen Kent has assumed the position of Head of Survey Coordination for the Sloan Digital Sky Survey and has overall responsibility for tracking survey progress and planning observations. He is additionally involved in various aspects of data processing, project management, telescope optics, and commissioning the telescope and imaging instruments. He is also head of the Experimental Astrophysics Group at Fermilab.

Edward J. Kibblewhite

My current research focuses on developing new techniques to achieve diffraction-limited imaging in fully filled apertures and distributed arrays of telescopes. The full resolution of ground-based telescopes will be achieved at near infrared wavelengths using a laser beam to generate an artificial star in the sodium layer of the earth's atmosphere. This star will enable the instantaneous wavefront of the atmosphere to be measured and these data used to correct for the atmospheric distortion using adaptive optics and post processing of the images. Faint objects can be studied with a resolution of 0.05 arcsecond using the ARC telescope. The system will allow fundamentally new observations of objects from planets to distant galaxies.

Baselines of hundreds of meters are needed to study the environment and surfaces of stars or the core of active nuclei. Distributed arrays of telescopes can provide such resolutions using synthesis techniques developed in radio astronomy. Such arrays pose formidable technical and system engineering problems requiring the development of stable telescopes, precision delay lines and correlators stable to nanometers over the short observation periods. A 5- or 6-telescope array is being planned using 0.6-meter telescopes operating in the near infrared.

Edward W. Kolb

The close collaboration between the Department of Astronomy and Astrophysics and the Astrophysics effort at Fermi National Accelerator Laboratory in nearby Batavia, Illinois exploits the close ties between particle physics and cosmology/astrophysics. The major effort of my research is the attempt to understand physical processes that occurred in the very earliest moments of the "Big Bang." In these very early moments the density, energy, and pressure of the universe resembled the conditions obtained in the collisions of particles at high-energy accelerators. The microphysics of the very early universe leaves its imprint on the present large-scale structure of the universe in the form of galaxies, the baryon asymmetry, element abundances, and structure in the cosmic microwave background radiation.

Arieh Königl

The physical processes underlying accretion and outflow phenomena in compact astronomical objects are being studied. These investigations bear directly on such issues as star formation, gamma-ray bursts, and the nature of active galactic nuclei. Since the material attracted by the gravitational pull of the compact object (be it a solar-mass protostar or a supermassive black hole) is typically rotating, it often settles into an ``accretion disk'' through which matter can continue to flow toward the center if there is a suitable mechanism for transporting away its angular momentum. Understanding the nature of such disks is a central research goal in view of its many potential applications. For example, in the case of protostellar disks, the structure of the accretion flow is directly relevant to the question of planet formation. Compact objects are frequently also found to give rise to energetic bipolar outflows, or jets, which propagate supersonically to large distances from the origin. In the case of gamma-ray bursts and ``blazar''-type active galactic nuclei, these jets can be highly relativistic. As the outflows are believed to be powered by the accretion process, another important theoretical goal is to construct self-consistent disk/jet models and to examine their implications to the dynamical evolution of the underlying systems. The interaction of the outflows with the surrounding medium is itself of great interest and may have significant observational consequences. Magnetic fields are thought to play a key role in the transport of angular momentum within the disk, in the ejection and collimation of the outflow, and in some cases also in the emission process. They therefore figure prominently also in the theoretical effort.

Richard G. Kron

Don Q. Lamb, Jr.

The focus of my research is the physics of matter and radiation under extreme conditions. Compact objects such as white dwarfs, neutron stars, and black holes provide an astrophysical laboratory for such studies. Their high internal densities enable non-ideal Coulomb solids, heavy nuclei, nuclear matter, and even quark matter to be probed. Hot dense matter is also crucial to an understanding of supernovae. The large gravitational potentials and the strong magnetic fields at the surfaces of these objects produce phenomena ranging from radio pulsars to active galactic nuclei. These phenomena can be used to test our understanding of nuclear reactions, hydrodynamics and shocks, and radiation transfer in magnetoactive and relativistic plasmas in new regimes, as well as to determine the properties, such as mass, radius, and magnetic field, of the compact objects themselves. My current research activities include projects in the following areas: properties of relativistic pair plasmas and hot dense matter; structure and evolution of degenerate dwarfs and neutron stars; supernovae, pulsars; X-ray emission from degenerate dwarfs and neutron stars; X-ray and gamma-ray bursts; and active galactic nuclei.

Stephan Meyer

The properties of the Cosmic Microwave Background Radiation (CMBR) is one of the best observables used to constrain the models of the evolution of the early universe. We are making measurements of both the anisotropy, and the low-frequency absolute temperature of the CMBR.

The absolute experiment is designed to complement the spectrum made by the COBE FIRAS experiment. In some circumstances, the thermal history of the plasma that existed before the production of the CMBR leaves a measurable distortion in the CMBR spectrum at low frequencies that can be detected by this measurement.

Anisotropy experiments have already constrained the magnitude of fluctuations at large scales. These fluctuations are presumably the starting points for the evolution of the structures we see today -- galaxy clusters, galaxies and stars. The current focus of anisotropy experiments at Chicago are to measure the CMBR variations at smaller angular scales. These measurements will determine whether the details of current evolution models are correct because they predict observable effects due to the dynamics of the matter as it evolves.

We are observing with a balloon-borne Medium Scale Anisotropy Measurement (MSAM) which has determined the magnitude of the 0.5-degree fluctuations with high sensitivity. The measurements are consistent with many of the current models and are indicating that the effect of the dynamics may be present.

We are currently building a new gondola called TopHat that will also fly on high-altitude balloons. It will be placed on the top of the balloon where the effects of instrumentation above the gondola are minimized. It will use a relatively new capability, Long Duration Ballooning (LDB) that permits flights as long as 20 days. This instrument will produce a map of the microwave sky and constrain the evolution models as well as determine several of the cosmological parameters that have long eluded precise measurement.

Richard H. Miller

Dynamics of Galaxies is a beautiful problem in Computational Physics. Beautiful objects (galaxies and star clusters) are studied by means of a beautiful formalism (Hamiltonian mechanics). Numerical experiments, carried out on self-consistent, self-gravitating systems by means of fully three-dimensional N-body computer programs, are the best tool available today for studies in the dynamics of galaxies, clusters of galaxies, and star clusters. These experiments play the same part for galaxy dynamics as do laboratory experiments in physics. The resulting programs are extremely versatile.

Important discoveries have come from this work. These include, among others (1) that the nucleus of a galaxy orbits around the galaxy's mass centroid, which can cause the nucleus to appear slightly off-center or to have a velocity that differs from the rest of the galaxy by tens of km/sec, (2) that galaxies oscillate in normal modes with surprisingly large amplitudes, (3) that the strong contractions evident in galaxy collisions are normal modes of oscillation, (4) that barlike forms are dynamically preferred for rapidly rotating self-consistent stellar systems while the traditional axisymmetric disk-like form is dynamically unstable, and (5) that the gravitational N-body problem is chaotic.

Dynamical studies to determine conditions under which a massive object (such as a supermassive black hole) will remain at rest at the center of a galaxy are the thrust of my recent research work. The observation that the nucleus of a galaxy orbits around the galaxy's mass centroid, mentioned in the previous paragraph, suggests that the black hole's being at rest is likely to be an unstable condition, with the black hole going into orbit in the neighborhood of the galaxy's mass centroid. We seek stability limits and hope to determine the amplitude and nature of the orbital motion in unstable cases. New experimental methods and techniques must be developed for each new problem. Designing and testing them is a challenging exercise, but new discoveries are likely to follow.

Takeshi Oka (See Department of Chemistry)

Angela Olinto

My work focuses on the interface between astrophysics, particle and nuclear physics, and cosmology. Over the last two decades, the combination of robust theoretical frameworks at this interface coupled with an unprecedented increase in the quality and quantity of observations over a wide range of frequencies has caused an unmatched growth in our understanding of the Universe. We have observed galaxies forming at the edge of the Universe, fine details of the relic cosmic backgrounds, and have started to narrow down the possible histories of how the Universe began. However, some major questions remain unanswered. Among the open questions, my research has focused on the origin of the highest energy particles ever observed, the origin of the magnetic fields that pervade all objects in the Universe, and the nature of the dark matter that constitutes most of the matter in the Universe.

Some subatomic particles that enter our atmosphere have so much energy that they produce a giant cascade of many tens of billions of secondary particles that can be observed by very large detectors on Earth. The particles that produce these giant air showers have been accelerated to far greater energies than can be achieved with terrestrial machines indicating incredibly powerful astronomical accelerators previously unforeseen. The explanation for the origin of these highest energy particles remains unclear. The possibility that these particles come from the edge of the observable Universe is limited by the presence of the microwave background that fills all of space and degrade the energy of such high-energy particles. The microwave background limits the location of these fantastic cosmic accelerators to relatively nearby in cosmological terms. The most plausible proposals range from supermassive black holes in centers of nearby galaxies to decaying particles left over from the Big Bang. We are searching for the answer by studying most plausible proposals in detail and aspects of the propagation from source to Earth. Propagation studies are intimately related to the knowledge of magnetic fields in the largest scales presently observed and particle physics models of interactions at the highest energies. Among plausible sources, we have proposed models that range from the most nearby possibility that these particles are iron accelerated in young fast spinning neutron stars from our own Galaxy to the possible effects of large extra-dimensions on the physics of these ultra-high energy cosmic rays.

The origin of magnetic fields that pervade all objects in the Universe is also still unknown. Magnetic fields may be generated in the very early universe through processes related to phase transitions or may be a more recent phenomenon related to the formation of the first collapsed objects. We have developed models of how magnetic fields are generated and how they evolve in the beginning of the universe. We can predict the role these fields have in the evolution of protogalactic structures but direct observations of the magnetic field relics is still a great challenge. Magnetic fields trace the turbulent history of the Universe being modified by the formation and evolutions of quasars, galaxies, and clusters of galaxies. The best probe of primordial fields is the study of the present field in intergalactic space away from the largest structures. The highest energy particles ever observed provide one of the best probes of the magnetic fields in the intergalactic medium today. We are studying how these Ultra-High Energy Cosmic Rays will open a new window into the evolution of the Universe.

Dark matter particles in the halo of our Galaxy can in principle be observed indirectly through the products of their annihilation. We have been studying alternative ways of detecting WIMP annihilation products in a wide range of wavelengths. This study may unravel one of the longest standing mysteries in modern cosmology.

Patrick E. Palmer

My work contains two related themes: star formation and the nature of comets. These themes are related both phenomenologically -- both involve study of cold, low density gases -- and at a deeper level -- comets provide the most pristine remaining samples of the material out of which our star, the Sun, formed.

During the spectacular apparition of comet Hale-Bopp in 1997, I participated in many collaborations using optical and radio telescopes around the world to collect data on this comet. We are still finishing up analysis and publication of this data.

One of the long-standing cometary mysteries is the origin of the CN radical, whose emission lines in cometary spectra have been identified for more that 50 years. A highly reactive molecule like CN cannot have existed in cometary ice for the age of the solar system. It must be a photo-dissociation product of a more complex, but more stable "parent" molecule. One reasonable possibility is HCN, but some have suggested that CN is produced by destruction of cometary dust. Recently, we have submitted a paper in collaboration with L. M. Woodney and Michael A'Hearn (U. of Md.), David Schleicher (Lowell Observatory), Lewis E. Snyder and J. Veal (U. of Illinois), Imke de Pater and M. Wright (U. C. Berkeley), and others in which we compared radio images of the HCN distribution obtained with the BIMA array with optical images of the CN distribution obtained at Lowell Observatory over a two week period around perihelion. We find that all data is compatible with HCN as the only parent.

In the past year, with W. Miller Goss (NRAO), I have begun several projects. These include a large area study of the star-forming region called W75, and several studies of interstellar masers.

The W75 region is very complex. There are recently formed stars, a wealth of interstellar H2O masers that are a signpost of ongoing star formation. Previous studies concentrated on a few of the most prominent maser sites and little was known about most of the area. In a series of observations over the past year, we have searched the entire area for these masers that turned up some additional masers and demonstrated how the masers sites fit with regions of dense gas and dust identified by others over the years. In addition, we observed maser emission from several transitions of interstellar OH. In particular, one of the transitions has proven to be an excellent indicator of shocked interstellar gas in supernova remnants. There are no supernova remnants in the region we observed, but there is a powerful outflow of shocked H2 molecules. Can the interaction with the H2 outflow produced the same C-type shocks that are observed in supernova remnants? We are investigating this possibility.

One of the most puzzling of the interstellar masers is H2CO. Only a few sources have been found in the Galaxy. Progress in understanding the maser mechanism is hindered by the lack of examples and because of lack of study at sufficiently fine angular scales. A few years ago, we conducted several sensitive searches but turned up no new examples. Last fall, we observed several of the known H2CO masers with the VLBA that provides sub-milli-arcsecond resolution (which corresponds to linear sizes of order the earth-sun distance at the distances of these masers). However, these observations showed that the masers are as large as 100 milli-arcseconds -- too large to provide good images with the VLBA, yet too small to resolve with the VLA. Therefore, we have proposed re-observing with the Merlin array in the UK, which when combined with the VLBA data we have will provide excellent images.

"An Interferometric Study of HCN in Comet Hale-Bopp (C/1995 O1)" Veal, J. M., Snyder, L. E., Wright, M., Woodney, L. M., Palmer, P., Forster, J. R., de Pater, I., and Kuan, Y.-J. 2000, Astron. J., 119, 1498.

"Water Emission from Comets" Graham, A. P., Butler, B. J., Palmer, P. and Strelnitski, V. 2000, Astron. J., 119, 2465.

"Radar Observations and Physical Modeling of Asteroid 6489 Golevka"' Hudson, R. S., Ostro, S. J., Jurgens, R. F., Rosema, K. D., Giorgini, J. D., Winkler, R., Rose, R., Choate, D., Cormier, R. A., Franck, C. R., Frye, R., Howard, D., Kelley, D., Littlefair, R., Slade, M. A., Benner, L. A. M., Thomas, M. L., Mitchell, D. L., Chodas, P. W., Yoemans, D. K., Scheeres, D. J., Palmer, P., Zaitsev, A., Koyama, Y., Nakamura, A., and Harris, A. W. 2000, Icarus, 148, 37.

"BIMA Array Photodissociation Measurements of Comet Hale-Bopp (C/1995 O1) " Snyder, L.E., Veal, J. M., Woodney, L. M., Wright, M. C. H., Palmer, P., A'Hearn, M. F., Kuan, Y.-J., de Pater, I., and Forster, J. R. 2001, Astron. J., 121, 1147.

"A Molecular Line Study of the HH \ 7-11 Outflow" Rudolph, A. L., Bachiller, R., Rieu, N. Q., Trung, D. V., Palmer, P., & Welch, W. J. 2001, Ap. J. (accepted: Apr. 28, 2001)

"Morphology of HCN and CN in Comet Hale-Bopp (1995 O1) " Woodney, L. M., Schleicher, D. G., A'Hearn, M. F., Farnhan, T. L., McMullin, J. P., Wright, M. C. H., Veal, J. M., Snyder, L. E., de Pater, I., Forster, J. R., Palmer, P., Kuan, Y.-J., Cheung, T. C., and Smith, B. R. 2001, Icarus (submitted, revised April 16, 2001).

Robert Rosner

R. Rosner and collaborators conduct both theoretical and observational research in solar and stellar astrophysics, more general plasma astrophysics, and fluid dynamics.

In the area of (astrophysical) fluid dynamics and magnetohydrodynamics, we have recently studied acceleration of ultra-high energy cosmic rays in the magnetospheres of neutron stars, the stability of accretion columns on such stars, and the stability properties of magnetized astrophysical jets. In the area of thermal convection, we have focused on both Boussinesq and fully compressible convection. For example, we have investigated in more detail the nature of "slot convection" at moderate and high Rayleigh numbers, and are now focusing on the problem of layering in convecting systems. In the area of magnetohydrodynamics, we have focused on problems related to turbulent magnetic field diffusion and dynamo processes. In addition, we are studying a variety of physical processes relevant to high-energy astrophysics, ranging from the dynamics of magnetic fields to transport processes in unstable fluid and plasma flows; for example, we are carrying out extensive studies of the nonlinear evolution of the Rayleigh-Taylor instability. We are also involved in the interpretation and modeling of astronomical observations, especially related to the activity of the Sun and late-type stars, as well as of other high temperature plasmas (such as in the magnetospheres of accreting compact objects and in the halos of clusters of galaxies). Our work typically involves both analytical calculations and (large-scale) numerical simulations.

As part of our efforts to better understand fluid and plasma processes relevant to astrophysics, we also study the corresponding fluid and plasma processes that can be explored in laboratory settings, and collaborate extensively with experimentalists in this area.

Our research group's home page is at http://astro.uchicago.edu/rranch/; the home page for the Center for Astrophysical Thermonuclear Flashes (of which I am the director) is located at http://flash.uchicago.edu.

Dynamo Action and the Period Gap in Cataclysmic Variables. A.F. Lanza, M. Rodono, and R. Rosner. MNRAS 314, 398, 2000.

Magnetic Fields of Stars: Using Stars as Tools for Understanding the Origins of Cosmic Magnetic Fields. R. Rosner. Phil. Trans. R. Soc. Lond. A 358, 689, 2000.

Evidence for Topological Nonequilibrium in Magnetic Configurations. S.I. Vainshtein, Z. Mikic, R. Rosner, and J.A. Linker. Phys. Rev. E 62, 1245, 2000.

On the Cellular Structure of Carbon Detonations. F.X. Timmes, M. Zingale, K. Olson, B. Fryxell, P. Ricker, A.C. Calder, L.J. Dursi, H. Tufo, P. MacNeice, J.W. Truran, and R. Rosner. ApJ 543, 938, 2000.

Kelvin-Helmholtz Instability in Three-Dimensional Radiative Jets. M. Micono, G. Bodo, S. Massaglia, P. Rossi, A. Ferrari, and R. Rosner. A&A 360, 795, 2000.

Numerical Simulation of Double-Diffusive Convection in a Rectangular Box. Y.-N. Young, and R. Rosner. Phys. Rev. E 61, 2676, 2000.

Flash Code: Studying Astrophysical Thermonuclear Flashes. R. Rosner, A. Calder, J. Dursi, B. Fryxell, D.Q. Lamb, J.C. Niemeyer, K. Olson, P. Ricker, F.X. Timmes, J.W. Truran, H. Tufo, Y.-N. Young, and M. Zingale. CiSE 2, 33, 2000.

The Sun as an X--ray Star. II: Using the Yohkoh/SXT-derived Solar Emission Measure vs. Temperature to Interpret Stellar X-ray

Observations. G. Peres, S. Orlando, F. Reale, R. Rosner, and H. Hudson. ApJ 528, 537, 2000.

On the Generation of Flux-Tube Waves in Stellar Convection Zones. III. Longitudinal Tube Wave-Energy Spectra and Fluxes for Late-Type Stars. Z.E. Musielak, R. Rosner, and P. Ulmschneider.ApJ, 541, 410, 2000.

FLASH: An Adaptive Mesh Hydrodynamics Code for Modeling Astrophysical Thermonuclear Flashes. B. Fryxell, K. Olson, P. Ricker, F.X. Timmes, M. Zingale, D.Q. Lamb, P. MacNeice, R. Rosner, J.W. Truran, and H. Tufo. ApJ Suppl. .131, 273, 2000

Ballooning Instability in Polar Caps of Accreting Neutron Stars. C. Litwin, E.F. Brown, and R. Rosner. ApJ in press, 2001.

Plasmoid Impacts on Neutron Stars and Highest Energy Cosmic Rays. C. Litwin and R. Rosner. PRL in press, 2001.

Noel M. Swerdlow

My general field of research is the history of the exact sciences, particularly astronomy, from antiquity through the seventeenth century. During the last two years my principal work has been a book on Renaissance astronomy that has become considerably longer than anticipated. It is to be published by the Burndy Library of the Dibner Institute for the History of Science and Technology through MIT Press and will contain many plates from books in the library so it should be quite handsome. The chapters are on the five principal astronomers of the period: Regiomontanus, Copernicus, Tycho, Kepler, and Galileo, and I have attempted as comprehensive descriptions of their work as I could within the limits of a general survey of this large subject. Nothing before has been done on this scale. As of writing this report, the chapters on Regiomontanus, Copernicus, Kepler, and Galileo are completed, and Tycho is in progress. I have also included translations of several texts that have not before been translated, of which the most important is Regiomontanus¹s Oration on the Mathematical Sciences given at Padua in 1464, I believe the most important single document on the relation of science and humanism in the Renaissance.

In addition to various articles, two projects, which I edited and to which I contributed, have recently appeared. One is the collection Ancient Astronomy and Celestial Divination published by MIT Press, a collection of papers presented at a conference at the Dibner Institute. The papers are on Babylonian astronomy and astrology and on Greek astronomy. The other, which took many years, is an edition, with Trevor Levered of the University of Toronto, of most of the published papers of Stillman Drake on Galileo and other subjects in the history of science. It is in three volumes running to over 1200 pages, published by the University of Toronto Press. As Drake was the greatest Galileo scholar of our age, the edition is an essential contribution to Galileo studies and to the history of science, and of course it can be reprinted indefinitely, a fitting tribute to Drake¹s work.

James W. Truran

The focus of my research is the attempt to understand the physical processes that are responsible for the synthesis of the heavy elements observed in nature. This necessarily involves the consideration of a broad range of problems in theoretical nuclear astrophysics. The high temperatures and densities achieved in stellar, nova and supernova environments are entirely compatible with the formation of heavy elements via nuclear processes; the sensitive dependencies of the resulting abundance patterns on the temperature, density, and convective history of the stellar matter and supernova ejecta demand that theoretical calculations of the nucleosynthesis yields must be coupled directly to hydrodynamic models of nova and supernova explosions. Many aspects of these problems are currently being studied by researchers at the ASCI/Alliances Center for Astrophysical Thermonuclear Flashes at the University of Chicago.

In order to view these studies of nucleosynthesis in individual events in perspective, it is further necessary to examination their implications for the composition of the stars and gas in galaxies as a function of time. Such studies of galactic chemical evolution are now increasingly tied to models of galactic dynamical evolution.

My current research activities include projects in the following areas: numerical simulations of thermonuclear runaways leading to nova outbursts; the consequences of hydrogen thermonuclear runaways on neutron stars (Type I x-ray bursts) for the synthesis of heavy proton-rich nuclei; r-process neutron-capture synthesis associated with supernovae or neutron star-neutron star mergers and its implications for nuclear dating of stars and star clusters; X-ray and gamma-ray emission from novae; nucleosynthesis in red giant (AGB star) environments; cosmic ray production of the light elements Li, Be, and B and galactic chemical evolution; nucleosynthesis and the observed compositions of metal deficient stars; the formation and early evolution of globular clusters; the chemical and dynamical evolution of the galactic halo; and thermonuclear reactions at high temperatures and densities.

Michael S. Turner

My research focuses on the application of modern ideas in elementary-particle theory to cosmology and astrophysics. I believe that this approach holds the key to answering the most pressing questions in cosmology. For example, there is reason to believe that the ubiquitous dark matter that holds the Universe together is elementary particles left over from the earliest moments, that the primeval inhomogeneity in the distribution of matter, which was revealed by COBE and which seeded all the structure in the Universe seen today, arose from quantum-mechanical fluctuations occurring during a very early burst of expansion called inflation, and that the existence of ordinary matter resulted from particle interactions in the early Universe that make the proton unstable and do not respect the symmetry between matter and antimatter. By testing these ideas with cosmological data, outer space becomes a window to the earliest moments of creation and to the unification of the forces and particles of Nature.

Over the next decade the search for particle dark matter, the mapping of the distribution of matter in the Universe a few hundred thousand years after the beginning through precision measurements of the cosmic microwave background radiation, and the mapping of structure in the present Universe by determining the positions of millions of galaxies should definitively test these bold ideas. Much of the crucial experimental work is being done by colleagues at Chicago; for example, the Sloan Digital Sky Survey will map the positions of a million galaxies and the DASI, TopHat, MAP, and Python experiments will measure the fine-scale anisotropy of the cosmic microwave background radiation.

Current specific areas of research include: big-bang nucleosynthesis in era of precision cosmology; theoretical aspects of inflationary cosmology; testing the inflationary paradigm; determining the nature of the dark energy that is causing the Universe to accelerate; dark matter and dark-matter detection; dark matter and the formation of structure in the Universe; the origin of the cosmic asymmetry between matter and antimatter; understanding how to use precision measurements of the fine-scale anisotropy of the cosmic microwave background and large-scale structure to probe inflation and fundamental physics; and aspects of axion, neutrino and string cosmology.

Selected Bibliography

1. Spontaneous Creation of Almost Scale-Free Density Perturbations in an Inflationary Universe (J. M. Bardeen, P. J. Steinhardt and M.S. Turner) Physical Review D 28, 679 (1983)
2. Supersymmetric Dark Matter Above the W-Mass (K. Griest, M. Kamionkowski, and M.S. Turner) Physical Review D 41, 3565 (1990)
3. Cosmological Baryon and Lepton Number in the Presence of Electroweak Fermion Number Violation (J.A. Harvey and M.S. Turner) Physical Review D 42, 3344 (1990)
4. The Early Universe (E.W. Kolb and M.S. Turner) (Addison-Wesley, 1990)
5. Constraints from Primordial Nucleosynthesis to the Mass of the Tau Neutrino (E.W. Kolb, M.S. Turner, A. Chakravorty, and D.N. Schramm) Physical Review Letters 67, 533 (1991)
6. Gravitational Waves from First-order Cosmological Phase Transitions (A. Kosowsky, M.S. Turner, and R. Watkins) Physical Review Letters 69, 2026 (1992)
7. Recovering the Inflationary Potential (M.S. Turner) Physical Review D 48, 5539 (1993) (astro-ph/9307035)
8. The Cosmological Constant is Back (L. Krauss and M.S. Turner) General Relativity and Gravitation 27, 1137 (1995) (astro-ph/9504003)
9. Cold Dark Matter (S. Dodelson, E.I. Gates, and M.S. Turner) Science 274, 69 (1996) (astro-ph/9603081)
10. CDM Models with a Smooth Component (M.S. Turner and M. White) Physical Review D (Rapids) 56, R4439 (1997) (astro-ph/9701138)
11. First Results of a High-sensitivity Search for Cosmic Axions (K. van Bibber et al) Physical Review Letters 80}, 2043 (1998) (astro-ph/9801286)
12. Big-bang Nucleosynthesis Enters the Precision Era (D.N. Schramm and M.S. Turner) Reviews of Modern Physics 70, 303 (1998) (astro-ph/9706069)
13. Probing Unstable Massive Neutrinos with Current Cosmic Microwave Background Observations (R.E. Lopez, S. Dodelson, R.J. Scherrer, and M.S. Turner) Physical Review Letters 81, 3075 (1998) (astro-ph/9806116)
14. Large-scale Structure from Quantum Fluctuations in the Early Universe (M.S. Turner) Phil. Trans. R. Soc. Lond. (1999) (astro-ph/9808149)
15. Cosmology Solved? Quite Possibly (M.S. Turner) Pub. Astron. Soc. Pac. 111, 264 (1999) (astro-ph/9811364)
16. Cosmology at the Millennium (M.S. Turner and J.A. Tyson) Reviews of Modern Physics 71, S145 (1999) (astro-ph/9901113)
17. Cosmic Rosetta Stone (C. Bennett, M.S. Turner, and M. White) Physics Today, November 1997, p. 32
18. Inner Space & Outer Space (M.S. Turner) Beamline, Fall 1997, p. 2
19. Sharpening the Predictions of Big-bang Nucleosynthesis (S. Burles, K. Nollett, J. Truran and M.S. Turner) Physical Review Letters, 82 (1999) (astro-ph/9901157)
20. Prospects for Probing the Dark-energy via Supernova Distance Measurements (D. Huterer and M.S. Turner) Physical Review Letters 82, (1999) (astro-ph/9808133)
21. Dark Matter and Dark Energy in the Universe (M.S. Turner) Physica Scripta, in press (1999) (astro-ph/9901109)
22. Constraining Dark Energy with SNe Ia and Large-scale Structure (S. Perlmutter, M.S. Turner, and M. White) Physical Review Letters 82, 1999 (astro-ph/9901052)

Peter O. Vandervoort

I am particularly interested in theoretical studies of the structures and the dynamics of galaxies. My purpose is to understand the forms and internal motions of galaxies as the consequences of the orbital motions of their constituent stars in response to the mutual gravitational attractions of those stars. This is accomplished through the construction of self-consistent, equilibrium models of galaxies. Stellar orbits in the prevailing gravitational field are the "building blocks" of such models, and their study is a central part of the subject. If a galaxy in equilibrium is unstable with respect to some small perturbation, then it cannot continue to exist in that equilibrium state. Therefore, my work includes studies of the oscillations and the stability of galaxies with a view to identifying those theoretical models which can provide viable representations of real galaxies. This research makes use of methods of mathematical analysis and numerical n-body calculations.

Donald G. York

Studies of the interstellar medium and intergalactic medium are underway using Earth-orbiting and ground-based spectrographs. For gas near the Sun, absorption lines of interstellar gas in stellar spectra are used to study abundances, ionization states, phases of the medium and the make-up of interstellar grains. A major program to identify the (probably) large molecules responsible for hundreds of unidentified, interstellar absorption lines (known as Diffuse Interstellar Bands), using all of the above information, is a special focus. The locations in space and the masses of interstellar clouds are being determined, using the FAME astrometric satellite.

Intergalactic gas, seen in absorption against background QSOs, is being used to probe and map halos of galaxies to determine the distribution of light elements that may be products of primordial nucleosynthesis, and to study the temperature, pressure, and element evolution in the gas between the galaxies. Studies of such absorption lines in spectra of distant QSOs aid in discovering high redshift galaxies, detectable in faint emission, given the redshift, using a tunable, imaging Fabry Perot system. The build-up of the elements through continuing nucleosynthesis is being used to chart galaxy evolution early in the history of the Universe.

For the next few years, the primary instruments used will be the FUSE (Far Ultraviolet Spectroscopic Explorer), to observe hot UV objects to about 14th magnitude; the ARC 3.5 meter telescope at Apache Point Observatory, with an echelle spectrograph and a Fabry-Perot imager; the 2.5 meter telescope (e) of the Sloan Digital Sky Survey (to construct a complete atlas of intergalactic absorption lines); and the Hubble Space Telescope STIS spectrograph, for studies of interstellar lines down to the FUSE magnitude limit.