Outer space#Intergalactic

As intergalactic medium (English: intergalactic medium - IGM, even intergalactic gas), referred to hydrogen gas, which is not bound to individual galaxies, but fills the space between them. It consists mainly of ionized Wasserstoff-Gas/-Plasma ( HII ); neutral hydrogen ( H or HI) accounts for only about one millionth of the entire medium.

The IGM should not be confused with the interstellar medium, which is located between the stars. However, the boundaries between intergalactic and interstellar media are fluid.

Classification

Warm- Hot Intergalactic Medium ( WHIM )

As WHIM is defined as the medium between individual galaxies. As an indication of the Intergalactic Medium one evaluates the Lyman-alpha forest in the spectra of distant quasars, optical or other active galactic nuclei. The absorption lines are generated by the neutral hydrogen that accumulates in the cosmic filaments.

2001 was discovered in a quasar signs of this Gunn -Peterson effect. However, this gas will have in the background radiation in the X-ray or may even show in the gamma range. Observations of X-ray satellites Chandra, however, show that at least 75 % of the background radiation in the hard X-ray in quasars, Seyfert galaxies or active galactic nuclei can be resolved. Thus there is not much room for a general intergalactic medium.

Intracluster medium ( ICM)

As intracluster medium is called the medium within galaxy clusters ( clusters ). Because of its relatively high temperature 107 to 108 K, the ICM can be observed by its X-ray radiation, which is produced as a bremsstrahlung. The gas is fully ionized and accounts for about 15% of the total mass of a cluster of. It is thus the dominant baryonic component in clusters of galaxies.