BH - BH is untraceable

Emmanuel Durodola
  • 4 Sep '22

I have been trying to track mergers in illustris, and it seems that galaxy mergers without BH - BH mergers are well documented, but the ones including BH mergers aren't? I have tried to use the numMergers function to parse this parameter space and it still only returns galaxy mergers with no black holes. For example, in TNG 100-3, subhalo 29 at snap 99 has one BH - BH merger at snap 32 but the information regarding the progenitors of that merger is nowhere to be found, but I can recover 5 galaxy mergers involving sub 29 at various snapshots that do not involve a BH - BH merger.

Dylan Nelson
  • 5 Sep '22


Can you clarify what you mean by "galaxy mergers without BH-BH mergers"?

The merger trees track subhalo mergers - they don't know, or care, about SMBHs.

Most massive central subhalos will host a SMBH, so if two such subhalos merge, their SMBHs will (likely) also merge.

Are you trying to connect SMBH-SMBH merger events from the "(f) Blackhole Mergers and Details" catalog, to subhalo mergers from the SubLink trees? If so, I imagine this will be quite difficult indeed.

Keep in mind, that subhalo 29 at snap 99 of TNG100-3 is a satellite, not a central. The ID of its (single) SMBH is 100108184884. Based on the BH_Progs field, it has had 2 progenitor SMBHs merge into this one.

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