This command can be used to mark those gas particles that are likely to be in galaxies.
Marked particles appear green in all plots.
Particles in a particular box can be unmarked using the unmarkbox command and all the marked particles can be unmarked using the unmarkall command. Particles remain marked even when a new time frame is loaded but after a new time frame is loaded any particles that were marked in the previous time frame can only be unmarked using the unmarkall command. Particles can also be marked using the markarray and markbox commands. Statistics about marked particles can be determined using the markstat command. Marked particles can be written to a file using the writemark command or read from a file using the readmark command.