Diffuse ionized gas

银河系中的DIG

• Referred to as the Reynolds layer, or warm ionized medium (WIM);
• This warm (10^4 K), diffuse (n ~ 0.2 cm~3) gas fills 20% of the disk volume and accounts for most of the mass of ionized gas(90 percent).

• 电子密度比hot gas要高一点（ Typical values of the central electron density, central cooling time and total mass for the ETGs are ~ 0.1cm−3, ~ 5 x 10^6 yr and 5 x 1O^9 M⊙）

• In terms of energetics, the Galactic WIM requires at least 10^42 ergs s~1 to remain ionized. This power is more than can be comfortably supplied by supernova shocks, but significantly less than the Lyman continuum luminosity of massive stars.
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