星系中的常见发射线

• [OII] doublet (3737A)
• [OIII] (4959A and 5007A)
• Balmer series (6563A, 4861A, 4340A, 4103A, ...).
• [NII]6583A
• [CII] 158$\mu$m fine-structure line

trace regions of active star formation and is the main coolant of the cold, neutral atomic medium.[1]

• 发射线的线比可以区分不同的电离机制，金属丰度 BPT diagram,详细的工作可参见[2]

红外谱线

• 精细结构线 [3]

The new [OIV]25.9μm/[OIII]88μm vs [NeIII]15.6μm/[NeII]12.8μm diagram is proposed as the best diagnostic to separate: i) AGN activity from any kind of star formation; and ii) low-metallicity dwarf galaxies from starburst galaxies.