Old Stellar Populations and Cosmology

点击翻译按钮获取中文摘要

Old stellar populations in galaxies will be studied and used as cosmological probes. The work falls logically into two areas: the study of old stellar populations and integrated spectra per se and the use of old stellar populations, specifically elliptical (E) and spherical (SO) galaxies, as tracers of irregularities in the local Hubble expansion of the universe. In the latter work, a project using E galaxies that has given evidence of a bulk motion at 600-700 km s-1 with respect to the cosmic restframe of a large sphere of galaxies around us out to 6000 km s-1 in radius will be expanded. This motion of the galaxies could provide a powerful constraint on cosmological theories and needs to be tested and probed in every possible way. To this end, a comprehensive analysis of N-body universe models as a means to illuminate potential pitfalls in Hubble flow studies of this type will be carried out. Completely new and independent estimates of the motions of nearby SO galaxies will be obtained to compare with those of Es. In the area of old stellar populations, a project will be continued to determine the metallicities and element abundance ratios in E galaxies and globular clusters. An empirical calibration of absorption-line features in G dwarf and K giant stars versus temperature, abundance, and surface gravity will be completed. These results will be compared to theoretical synthetic spectra, and, when a satisfactory understanding of stellar spectra is achieved, there will be a synthesizing of integrated spectra of galaxies. Long-slit spectra of elliptical galaxies will also be analyzed for radial abundance gradients, and new, high-quality, high-resolution stellar spectra will be used to explore small composition differences among globular cluster stars.