the Massive Black Holes workshop at KITP continues, with another Black Hole Pairs session

Mike Eracleous kicks off: Observational Searches for Close Supermassive Binary Black Holes

emission line signatures of close (~ sub-parsec) supermassive binary black holes

cf “A Large Systematic Search for Recoiling and Close Supermassive Binary Black Holes”
and “Emission Lines as a Tool in Search for Supermassive Black Hole Binaries and Recoiling Black Holes”

look for single line emitters, broad emission line displaced from narrow emission lines – displacement is ~ 1,000 km/sec
orbital periods of order decades-to-centuries
look for accelerations – with primary masses of ~ 100 million solar masses expect acceleration order 20 km/sec/sec – modulo trig projection factor
cross-correlate spectra to look for subtle shifts

get a large sample, find some with favourable geometry if lucky
see acceleration with multi-year monitoring
several groups doing monitoring, underway

four groups doing searches, all have some interesting candidates with properties broadly consistent with binaries
statistics not robust yet

need longer baseline and multi-wavelength observations
could be faked out by disks around single SMBH doing their funky things

but… if these are not the binaries we are looking for
then where are they? they’ve got to be somewhere…


Julia Comerford: Observations of Dual Supermassive Black Holes at kpc scale serparations
looking for widely separated SMBH – before they become bound into a tight binary – post galaxy merger remnants

Swift BAT survey – 10% of low z AGN are dual
quarter of those within 10 kpc (projected)

looks like lower limit of 0.1% of AGN are dual AGN

Back from break

Laura Blecha (UMd) on A candidate recoiling black hole in a nearby dwarf galaxy

ok, moving on the gravitational radiation and recoil
does the post-coalescence SMBH recoild from the centre of the galaxy
at interesting velocities due to gravitational radiation recoil

well, yes, depending on mass ratio and spin alignment
but, how many and how fast…

leaves you, for a while, with a galaxy with no central SMBH – those are rare
and a naked SMBH – which may accrete significantly for a few Myr if it carries significant material with it

Two galaxies have kinematic and spatial offset AGNs that may be robust
recoil candidates

CID-42 Civano et al 2010
“A Runaway Black Hole in COSMOS: Gravitational Wave or Slingshot Recoil?”
“Chandra High resolution Observations of CID-42, a candidate recoiling SMBH”
“Constraints on the Nature of CID-42: Recoil Kick or Supermassive Black Hole Pair?”

and Koss et al in prep in anonymous galaxy
second one is 0.8 kpc projected offset in blue dwarf galaxy (star forming)
lines off by few hundred km/sec
interesting looking spectrum

looks not implausible as genuine recoil candidate
watch the arXiv!

mass of just under 106disc ratio as critical parameter
and varying with black hole mass
making some assumption I didn’t catch, guess I’ll have to go read the paper

“On the orientation and magnitude of the black hole spin in galactic nuclei”

Tal Alexander: Stars, disks and black holes
importance of stellar interactions with SMBH
contrast with gaseous disks

yeah, you need to account for both
It is messy.
I have not said messy often enough yet.