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SUMMARY:Fact or FABLE: predictions for SMBH merger rates from cosmological
  simulations - Stephanie Buttigieg / IoA
DTSTART:20250212T131500Z
DTEND:20250212T134000Z
UID:TALK228295@talks.cam.ac.uk
CONTACT:Xander Byrne
DESCRIPTION:The co-evolution of massive black holes and their host galaxie
 s is well established within ΛCDM cosmology. The repeated mergers\, accre
 tion\, and feedback that conspire to regulate this process can be studied 
 in large-scale cosmological simulations\, such as Illustris\, FABLE\, Mill
 enniumTNG and Flamingo. These simulations resolve key galaxy formation pro
 cesses at ~kpc scales\, but are plagued with numerical inaccuracies at the
  smaller scales of black holes. This scale discrepancy presents significan
 t challenges for investigating black hole properties and generating testab
 le predictions\, e.g. for future JWST\, Gaia\, LISA and IPTA observations 
 of isolated and binary black holes. In this talk I will discuss the black 
 hole population in FABLE. Our results show that the numerical treatment of
  black holes in cosmological simulations leads to a misleading picture\, e
 ven at the well-resolved large scale of galaxies. In particular\, a large 
 fraction of black holes coalesce well before their host galaxies merge and
  thus require extra delays on the order of a few Gyrs. These delays\, gove
 rned by the dynamical timescale of the merging host galaxies\, occur befor
 e and in addition to any delays arising from unresolved ‘sub-grid’ phy
 sics describing BH hardening mechanisms on parsec scales. This effect has 
 profound implications for the black hole merger rates predicted from these
  large-scale cosmological simulations as well as for the multi-messenger p
 redictions\, once black hole growth during these dynamical galaxy merger d
 elays is accounted for.
LOCATION:The Hoyle Lecture Theatre + Zoom 
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