Formation of galactic nuclei with multiple supermassive black holes at high redshifts

Understand

We examine the formation of groups of multiple supermassive black holes (SMBHs) in gas-poor galactic nuclei due to the high merger rate of galaxies at high redshifts.

• We calculate the relative likelihood of binary, triple, and quadruple SMBH systems, by considering the timescales for relevant processes and combining merger trees with N-body simulations for the dynamics of stars and SMBHs in galactic nuclei.
• Typical haloes today with mass $M_0\approx 10^{14}$ M$_\odot$ have an average mass $M_{z=6}=5\times 10^{11}$ M$_\odot$ at $z\sim 6$, while rare haloes with current mass $M_0\gtrsim 10^{15}$ M$_\odot$ have an average mass $M_{z=6}=5\times 10^{12}$ M$_\odot$ at that redshift.
• These cluster-size haloes are expected to host single galaxies at $z\sim 6$.