Astrophysical theory is intellectually vibrant, and productivity is high: about 45 percent of published papers are on theory, and about one-third of publishing astronomers are pursuing theory (see Figure 4.9). Based on the recent record, there is a compelling case that investments in theory by the agencies will be amply repaid in the form of new mission and experiment concepts and enhanced scientific return from operating facilities. Astrophysical theory draws some of the world’s best intellectual talent into the U.S. scientific enterprise. Because some of the most important theory contributions in the next decade will come from broadly based theory not specifically tied to large activities, the role of general individual investigator programs will continue to be as important as ever. These programs form the traditional base of theoretical astrophysics in which Ph.D. students are trained, new ideas arise, and future observational or experimental efforts are seeded.
Astrophysics and cosmology theory is supported through a number of programs at the federal agencies. At NSF, general astrophysics theory is funded through the AST Astronomy and Astrophysics Research Grants (AAG) program,5 as well as through the NSF Division of Physics (NSF-PHY) via its Frontier Centers and individual investigator grants in cosmology and particle physics theory. At NASA, the Astrophysics Theory Program (ATP) supports most general theory efforts. In addition, the Hubble, Spitzer, Chandra, and Fermi Observatories accept theoretical investigations as part of their guest investigator programs. Other critical support comes from NASA Prize Postdoctoral Fellowship programs (Einstein, Hubble, Sagan). The DOE’s Office of High Energy Physics also supports theoretical and computational astrophysics efforts. Table 5.2 summarizes current funding levels.
As is the case with the grants programs in general, proposal success rates in theory have declined over the past decade. The recent success rate in NASA’s ATP is only 15 to 20 percent, significantly lower than funding rates for theory within its Planetary Exploration program, for example. Given the central importance of theory to the enterprise, and the crucial role played by individual investigator grants, the committee recommends in Chapter 7 that the grants programs at both NSF and NASA be augmented.
The dramatic impact of computation on astronomy and astrophysics is manifested in many ways. Modern numerical codes are now being used to simulate and