Recession velocities for fossil galaxy groups

Defined as X-ray bright galaxy groups with large differences between the luminosities of their brightest and second brightest galaxies, "fossil groups" are believed to be some...“化石群（fossil groups）被定义为最亮星系与第二亮星系之间光度差异显著的X射线亮星系群，这类天体被认为是一类……”