Planning a Large-Scale Near-Infrared Survey

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Main topics of this research comprises studies of brown dwarfs, an interpretation of stellar objects in a near-infrared deep survey, and the sensitivity analysis of an imaging space infrared interferometer.From the study of young brown dwarfs, it became clear that brown dwarfs are formed both as isolated objects and as companions to more massive objects. We analyzed the potentials of space missions for brown dwarf research and found that space missions are capable of detecting many cold brown dwarfs, while ground based observations are sensitive only to warm brown dwarfs. We otained time resolved spectra of the cool brown dwarfs, SDSS 1624+00 to study weather in this brown dwarf. Although the time span was as short as 80 minutes, we were able to detect some variability.A deep survey of a small area is complementary to a wide-field survey in the sense that the deep small-field survey elucidate the universe at faint magnitudes. By constructing star count models from the data of the deep survey, we can predict stellar/substellar populations found by surveys in general. The models we generated predict the brown dwarf count of the UKIRT Wide Field Survey and depict the Galaxy seen by the Next Generation Space Telescope.The ultimate instrument to follow up objects found by a survey with high angular resolution is a space interferometer. The space interferometer can perform a deep survey in the far infrared and count galaxies to study cosmology. We first derived formulae of sensitivities of space infrared interferometers and then applied them to study the performance of currently planned Terrestrial Planet Finder and Darwin. We found that radiation cooled interferometers are more sensitive than cooled telescopes and cooled interferometers are capable of studying observational cosmology.