The origin and evolution of fast and slow rotators in the Illustris simulation

摘要: Using the Illustris simulation, we follow thousands of elliptical galaxies back in time to identify how dichotomy between fast-and slow-rotating ellipticals (FRs and SRs) develops. Comparing ATLAS(3D) survey, show that reproduces similar galaxy rotation properties, quantified by degree ordered rotation, lambda(R). There is a clear segregation low-mass (M-* 10(11.5) M-circle dot), which are mostly SRs, agreement with observations. We find SRs very gas poor, metal rich red colour, while FRs generally more still star forming. suggest begin naturally as and, they grow mass, lose their spin become SRs. While at z = 1, progenitors nearly indistinguishable, merger formation histories differ thereafter. major mergers tend disrupt spin, though rare cases can lead spin-up. No difference found effects gas-rich gas-poor mergers, number minor seems have little correlation spin. In lower mass ellipticals, rich, recover accreting stars. For M* above 10(11) dot, this trend reverses;galaxies only retain or steadily More frequent accompanied an inability regain massive most transition from