Dark areas around bright objects

I often see dark areas around bright objects. I have been saying that this is part of the clean up process. Is this correct?

For example, around this red star, which has a dark area around it, apparently changing the shape of a galaxy.



Of course, a star is close and smaller than a pixel on this image, and can’t be blocking light from a galaxy.
So, a trickier example, this smaller galaxy is apparently blocking some of the light of the larger galaxy. Is this dust of the smaller galaxy blocking the light, or is it due to clean up artifacts?