User:Mike Peel/Radio Recombination Lines

Radio Recombination Lines (RRLs) are spectral lines emitted during recombination (Plasma recombination?). They are observed at radio frequencies.

Lines

 * Due to the formation of atoms through the recombination of electrons and ions
 * Lines come from transitions between highly excited atomic levels.
 * At radio frequencies, referred to as 'Radio Recombination Lines'.
 * Emitted by hydrogen atoms
 * In the interstellar medium, can have quantum levels up to n=1000, and with radiuses of the order of a tenth of a millimetre.
 * Maser effects
 * Low frequencies contaminated by synchrotron emission.

Implications

 * Probe of the gas in star-forming regions.
 * Depends on gas densities and temperatures.
 * Can estimate electron temperatures.
 * Can estimate star formation rates.
 * Dust attenuation

Solar system

 * Detected in the Sun.

Galactic regions

 * Galactic HII regions
 * Galactic plane

Nearby galaxies
The first extragalactic detection of RRLs beyond the Magellanic clouds was the H166α line in Messier 82 in 1977.