0 Cold gas , the HI 21 cm line and evolving galactic potentials
نویسنده
چکیده
Neutral hydrogen traces gravitational potentials. In the nearby universe, 21cm emission-line surveys show that the bulk of the HI resides in well-formed, optically-luminous galaxies. At high redshift, 21cm line absorption against background radio quasars occurs in gas-rich systems identified with the highest HI column densities – the " damped Lyman alpha " quasar absorption-line systems. High spatial-resolution observations of the red-shifted 21cm line absorbers measure sizes and kinematics of the neutral absorbers.
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