PAH

• PAH 的辐射

3.3um C-H键震动，脂肪族的C-H键震动在3.4um

6.2,7.6um是C-C拉伸震动

7.8,8.6 C-H在平面内弯曲，11.3,12.7平面外弯曲

17um,C-C-C弯曲，18mu有硅的发射特征

• tight correlation of PAH and CO emission from z ∼ 0 to 4 [1]

• PAH和CO与IR光度的关系都是sub-linear的，MIR的光度中有AGN的贡献

• PAHs are better suited as a tracer of B stars than as a tracer of massive SF. They probe star formation activity time scales of up to 100Myr. [2]

• Mapping RPAH across the 19 PHANGS galaxies, we find that the PAH fraction steeply decreases in HII regions, revealing the destruction of these small grains in regions of ionized gas. Outside HII regions, we find RPAH is constant across the PHANGS sample with an average value of 3.43±0.98, which, for an illuminating radiation field of intensity 2-5 times that of the radiation field in the solar neighborhood, corresponds to qPAH values of 3-6%. arXiv:2405.15102

• PAHFIT