ELFT HÍRADÓ

[szpl <szpl AT metal.elte.hu>]

ELTE Fizikai Intézet

                                ORTVAY KOLLOKVIUM

                    2018. március 8., csütörtök, 15:00-kor
                Az ELTE Pázmány Péter s. 1/A alatti épületében
                           földszinti 0.81 előadóban



                        Haiman Zoltán (Columbia University)

                Supermassive Black Hole Mergers in Galactic Nuclei

Kivonatos ismertetés:
Astronomers have found that most major galaxie harbor supermassive black holes
(SMBHs) at their centers, with masses between a million to a billion times 
that of the Sun.  Galaxies are also known to often collide and merge, creating
compact SMBH binaries.  These binaries are not directly resolvable by 
conventional electromagnetic telescopes, and observational evidence for their 
existence remains elusive. However, they are sources of strong gravitational 
waves (GWs), which can be detected in the future, e.g. by instruments such as 
the space-based interferometer LISA.  Identifying the host galaxies of these 
GW sources is a major goal of astrophysics and cosmology, which would allow 
us to track the role of mergers versus gas accretion in the build-up of massive
black holes over cosmic time, and provide novel tests of general relativity 
on large distance scales.  In this talk, I will argue that compact nuclear 
SMBH binaries are typically surrounded by dense gas, and discuss the coupled 
dynamics of a SMBH binary with a circumbinary gas disk.  I will show that the 
gas disk can extract the binary's orbital energy and angular momentum, and 
promote its inspiral to small separations.  I will also discuss the expected 
characteristics of EM emission from such a system, which differs markedly from 
the emission of a solitary SMBH.  In particular, the binary's emission is 
highly time-variable, and contain unique spectral signatures, which should aid 
in their identification.  A handful of quasars have recently been identified 
with periodic optical variability on the timescale of O(year). I will comment 
on the interpretation of these quasars as SMBH binary candidates.