Zombie processes detectable in dom0

I noticed that some programs leave traces in dom0. Some cli utilities, namely ps and top, detect them as zombie processes. It happens after some disposable VMs are shutdown, after I close Qubes Manager, and after I use the GUI update mechanism. As far as Qubes Manager goes, the process seems to be “resurrected” if I start it up again. It then reappeares when I close it again.

Are they truly zombies, are they simply reserved, or is it something else?