The effect of AGN feedback on shape of dark matter haloes

Abstract

Feedback from active galactic nuclei (AGN) plays an important role on the formation and matter distribution in haloes. We investigate the effect of AGN feedback on shape of dark haloes formed in the EAGLE simulations, and trace the evolution. We select three mass ranges of haloes; low (1011 − 1011.5M⨀), intermediate (1012 − 1012.5M⨀) and high (1013 − 1014.5M⨀) mass, the last range is of small cluster scale. We find the median profile of triaxiality in each mass range at three redshifts (0, 0.27 and 0.87) from two simulations, with and without AGN. The difference of triaxiality in both simulations of low mass haloes at all redshifts is relatively not apparent while the most apparent difference exhibits in high mass haloes. The shape of dark matter haloes in the simulation with AGN is more prolate than that in the simulation without AGN. We also use the ratio between blackhole and dark matter mass, relating to AGN energy output relative to halo potential depth to explain the result. Since the mass ratio between blackhole and dark matter mass in the high and intermediate mass is much larger and extends to the larger radii than that of low mass haloes, the difference is more prominent out to the outer region. We conclude that the shape of dark matter haloes of small cluster scale can be affected by AGN feedback through the evolution. However, this study focuses on an extreme AGN feedback model with a relatively small dynamical range.