The Stratospheric Terahertz Observatory (STO): An LDB Experiment to Investigate the Life Cycle of the Interstellar Medium

摘要

The Stratospheric Terahertz Observatory (STO) is a balloon-borne, 0.8-meter telescope designed to investigate the structure of the interstellar medium and the life cycle of interstellar clouds. In its first long duration flight, STO will use two, 4-beam HEB receiver arrays to survey part of the Galactic Plane in the [C II] line at 158 microns (the brightest spectral line in the Galaxy) and the [N II] line at 205 microns (a tracer of the star formation rate). At ～1' angular resolution and < 1 km/s velocity resolution, STO will detect every interstellar cloud with A_v > 0.3 in the surveyed region, and, through excitation and kinematic diagnostics provided by [CII] and [N II] line emission, will illustrate how atomic and molecular clouds are formed and dispersed in the Galaxy. STO will make 3-dimensional maps of the structure, dynamics, turbulence, energy balance, and pressure of the Milky Way's Interstellar Medium (ISM), as well as the star formation rate. In future flights, STO will observe the important far-infrared lines of [O I|, [N II], and HD.