Dancing to changa: a self-consistent prediction for close SMBH pair formation time-scales following galaxy mergers Article Swipe
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· 2018
· Open Access
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· DOI: https://doi.org/10.1093/mnras/sty139
· OA: W2748435155
We present the first self-consistent prediction for the distribution of\nformation timescales for close Supermassive Black Hole (SMBH) pairs following\ngalaxy mergers. Using ROMULUS25, the first large-scale cosmological simulation\nto accurately track the orbital evolution of SMBHs within their host galaxies\ndown to sub-kpc scales, we predict an average formation rate density of close\nSMBH pairs of 0.013 cMpc^-3 Gyr^-1. We find that it is relatively rare for\ngalaxy mergers to result in the formation of close SMBH pairs with sub-kpc\nseparation and those that do form are often the result of Gyrs of orbital\nevolution following the galaxy merger. The likelihood and timescale to form a\nclose SMBH pair depends strongly on the mass ratio of the merging galaxies, as\nwell as the presence of dense stellar cores. Low stellar mass ratio mergers\nwith galaxies that lack a dense stellar core are more likely to become tidally\ndisrupted and deposit their SMBH at large radii without any stellar core to aid\nin their orbital decay, resulting in a population of long-lived 'wandering'\nSMBHs. Conversely, SMBHs in galaxies that remain embedded within a stellar core\nform close pairs in much shorter timescales on average. This timescale is a\ncrucial, though often ignored or very simplified, ingredient to models\npredicting SMBH mergers rates and the connection between SMBH and star\nformation activity.\n
