EPISODIC ACTIVITIES OF SUPERMASSIVE BLACK HOLES AT REDSHIFT z 2: DRIVEN BY MERGERS?

摘要: It has been suggested for quite a long time that galaxy mergers trigger activities of supermassive black holes (SMBHs) on the grounds imaging observations individual galaxies. To quantitatively examine this hypothesis, we calculate quasar luminosity functions (LFs) by manipulating observed LFs (z 2) and theoretical merger rates from semi-analytical formulations. We find model reproduces provided mass ratio (q) secondary to newly formed one changes with cosmic time. The results show fraction major decreases f maj ~ 0.2 at z 2 → 0 0. As consequence, SMBHs may acquire maximal spin due orbital angular momentum merging holes. Subsequently, random accretion led minor rapidly drives down. Such an evolutionary trend SMBH spins is consistent fact radiative efficiency accreting strongly declines time, reported Wang et al. This suggests are important in triggering low redshift, while dominate high redshift.