Title :
Absorption Techniques as a Tool for 21-CM Research
Author :
Lilley, A.E. ; McClain, E.F.
Author_Institution :
Yale University Observatory, New Haven, Conn. Formerly with Radio Astronomy Branch, U. S. Naval Research Lab., Washington, D.C.
Abstract :
Hyperfine transitions between the F = 0 and F = 1 levels of interstellar hydrogen gas have been observed to produce absorption lines in the spectra of radio stars. Elementary relations are developed which describe the action of an L band radiometer connected to an antenna, if the antenna is viewing an assembly of gas which is illuminated by a radio star. The consequences of the absorption line studies are reviewed. They include: high resolution studies of the interstellar gas, the structure and physical state of interstellar HI regions, minimum distances to radio stars, and experiments of interest in cosmology.
Keywords :
Atomic measurements; Australia; Electromagnetic wave absorption; Hydrogen; Radiation detectors; Radio astronomy; Radiometry; Senior members; Temperature; Wavelength measurement;
Journal_Title :
Proceedings of the IRE
DOI :
10.1109/JRPROC.1958.286738
