Ph1 - Universität zu Köln
[OI] self-absorption effects in M17SW and MonR2
Using the unique capabilities of upGREAT/SOFIA, we have observed simultaneously both oxygen atomic transition, [OI] 145 and 63 um lines towards M17-SW and Mon-R2. We found that [OI] 63 um is severely affected by self-absorption effects due to its optically thick emission, compared to the optically thin [OI] 145 um. Through a multi-component Gaussian fit analysis, we separate the emission into two layers, a background layer in emission and a foreground layer in absorption. We found high column densities in emission, plus cold and high column density material in absorption, of puzzling origin, also detected previously from [CII] and [13CII] observations.