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| Observational and Theoretical Cosmology and the Early Universe | ||
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Associated Faculty and
Web Pages listed below.
Cosmology addresses fundamental questions about the nature and evolution of the universe. Faculty and students at the CfA contribute to the dynamism and excitement of the field. Large Scale Structure. The CfA redshift survey with the 1.5-m telescope on Mt. Hopkins uncovered surprising large-scale coherent patterns in the distribution of galaxies. To answer the many questions raised by these surveys, exploration of the more distant universe continues from Mt. Hopkins and from international facilities in Chile, including the Las Campanas Redshift Survey and the 2MASS Redshift Survey. Structure Formation: Initial conditions. Analyses of these data continue to challenge theorists who model the development of structure in the universe. Measurements of the cosmic microwave background (CMB) and CMB anisotropies provide a snapshot of the universe when it was very smooth and young. These anisotropies may be generated by quantum fluctuations, providing a link between particle physics at very high energies and cosmology. Several researchers at Harvard and at the CfA are pursuing that link theoretically and participating in analyses of current and upcoming CMB measurements. The analyses span a range of topics, from mechanisms and theories for the primordial fluctuations and the physics of recombination to frameworks for data analysis and optimal future observing strategies. Structure Formation: Evolution. The initial perturbations grow via gravitational instability to form a 'cosmic web' of structure on many scales. Numerical approaches, including the use of a custom built set of machines in the department, are being developed to calculate properties of this evolving structure. Questions of interest include the characteristics and measurable consequences of the first luminous objects and the structure of the Lyman-alpha forest. First light of the 6.5-meter converted MMT in 1999 will enable faculty and students to explore the young universe directly. Researchers at the CfA also study the formation of galaxies, from high redshift up to the present day, and more recently formed (and larger) structures such as galaxy clusters. X-Ray observations of these systems with ROSAT (the data archives are at the CfA) and the Chandra X-Ray observatory provide another route to understanding the development of structure in the universe.
Expansion of the Universe. The expansion of the universe is controlled by the amount and type of energy it contains. From the initial observations at Mt. Hopkins, gravitational lenses have become a tool for limiting and mapping the distribution of the ubiquitous dark matter in the universe. The Hubble constant is the target of several projects of Department and CfA members, such as the Hubble Key project, time delays from strong gravitational lensing, and complementary studies of determinations of the extragalactic distance scale, described under extragalactic astronomy. By using type Ia supernovae as standard candles, the High Z Supernovae group has found evidence for an accelerating universe, which may be due to a cosmological constant. Theory is advancing with the influx of data and the development of better and better numerical tools and methods, with CfA and Department members on the forefront, and observers continue to plan and create more powerful probes of the distant, young universe. See also the related area of extragalactic astronomy. Associated Professors and Lecturers
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