“Massive black hole pairs” is the topic of today’s session at the BHOLES13 workshop at KITP

Talks are online here – note that slides of talks show up later as speakers get their act together and send in slides

Monica Colpi (Milan) starts the session with Formantion of Binary Black Holes in Galactic Nuclei

starts off with good summary of “last parsec” problem and why it is a bit of a red herring
followed by discussion of role of gas at late stage of mergers and summary of sims
new trendy things to do is to look at star formation in situ in outer accretion disks – something must happen, but it is a hard problem, messy

going to be using the word “messy” a lot today

spin-orbit alignment is rapid during gaseous phase – this is important because of grav rad recoil – spin aligned BH coalescence usually has low gravitational radiation recoil (depend on mass ratio, natch, but fairly strong function)

cool movie

good summary of issues at earlier stages of merger – astrophysics of the galaxy collision and gas dynamics, dynamical friction and star formation in the early stages of post galaxy merger phase – very nice

remember the talks are online, both web and slides – I’ll put up links – slides can take a while to appear

somewhat controversial assertion – early states of merger for mass ratio q < 0.1 are delayed because of delay in BH finding each other - I'd have thought you could go to considerable lower q before there is a problem at this stage

very nice review

Jorge Cuadra (PUC) is next: massive black hole binary mergers within sub-pc scale disks

talks about recent sims of gas rich mergers, formation of gaseous disks with BH pair embedded - talk will focus on late stage of mergers

Ed comment: the early gas rich merger sims tend to focus on 1:1 or 3:1 mass ratio because that is mostly what we can do, also with both galaxies spiral and gas rich
the harder problem of gas rich dwarfs merging with large gas poor early type galaxies is mostly ignored though probably much more relevant to most astrophysical mergers
#GoodProblemForGradStudent - someday

another editorial comment: sims tend to use very massive gas disks, because they can, and these tend to be unstable, natch, and to evolve rapidly
disks we see around SMBH tend to have much lower masses, but then of course we are biased to seeing the stable long lived disk phases

sims agree with Syer & Clarke (1995) predictions

Cuadra sims show linearly growing eccentricity - reach e ~ 1/3 by end of sims

I find that worrying

starting at high eccentrcities shows damping
infer, from limited sim data that eccentricity will asymptote to ~ 2/3
heuristic explanation based on δρ and torques at corotation

eccentric orbits drive episodic accretion, primarily onto secondary, with characteristic time scale of binary orbital period

role of stars formed in fragmenting disk
more cool movies

Fazeel Khan (IST) - SMBH binaries in axisymmetric galaxies

binary SMBH in our "squeezed" γ=1 models, q=1
axis ratios of 0.9, 0.8 and and 0.75, N=125k-1M
Phi-GRAPE direct N-body code
relaxation converges for N large enough, looks like
hardening faster in flatter models

After break:
Brendon Kelly (UCSB) on BH growth and mass function
Daniel Angles-Alcazar (UoA) on self-regulated BH growth

Man, messed that one up – missed first part of that session
talks were actually:
Davide Fiacconi (Zurich) on Evolution of massive black hole pairs in clumpy environments: from circumnuclear disks to major mergers
and
Pedro Capelo (Michigan) on Nuclear coups in unequal mass galaxy mergers

Akos Bogdan (CfA) SMBH and bulge evolution
No, it is David Ballantyne bounced from Thursday’s slot talking on mergers and secular processes in AGN evolution…

I was off politicking no summaries of these, sorry.