Given its velocity dispersion , the early-type galaxy NGC 1600 has an unusually massive ( M _ { \bullet } = 1.7 \times 10 ^ { 10 } M _ { \odot } ) central supermassive black hole ( SMBH ) , surrounded by a large core ( r _ { \mathrm { b } } = 0.7 kpc ) with a tangentially biased stellar distribution .
We present high-resolution equal-mass merger simulations including SMBHs to study the formation of such systems .
The structural parameters of the progenitor ellipticals were chosen to produce merger remnants resembling NGC 1600 .
We test initial stellar density slopes of \rho \propto r ^ { -1 } and \rho \propto r ^ { -3 / 2 } and vary the initial SMBH masses from 8.5 \times 10 ^ { 8 } to 8.5 \times 10 ^ { 9 } M _ { \odot } .
With increasing SMBH mass the merger remnants show a systematic decrease in central surface brightness , an increasing core size , and an increasingly tangentially biased central velocity anisotropy .
Two-dimensional kinematic maps reveal decoupled , rotating core regions for the most massive SMBHs .
The stellar cores form rapidly as the SMBHs become bound , while the velocity anisotropy develops more slowly after the SMBH binaries become hard .
The simulated merger remnants follow distinct relations between the core radius and the sphere-of-influence , and the SMBH mass , similar to observed systems .
We find a systematic change in the relations as a function of the progenitor density slope , and present a simple scouring model reproducing this behavior .
Finally , we find the best agreement with NGC 1600 using SMBH masses totaling the observed value of M _ { \bullet } = 1.7 \times 10 ^ { 10 } M _ { \odot } .
In general , density slopes of \rho \propto r ^ { -3 / 2 } for the progenitor galaxies are strongly favored for the equal-mass merger scenario .