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February 28, 202211:30 am – 12:30 pm (CDT)

Do Some SMBH in Nearby Galaxies Come in Pairs? – An Observer’s Tale


Sabine Thater (University of Vienna)


Jonelle Walsh

Event Details

The formation of supermassive black holes (MBH) is thought to be tightly linked to the formation and growth of their host galaxies. While it is difficult to infer information about MBHs, galaxy evolution often leaves an imprint on the host galaxy properties. One of those properties is that the most massive galaxies often show 'cores' in their central surface brightness profiles. Instead of a continuously steep power-law surface brightness cusp, core galaxies show a shallow central light profile, depleted in stars with respect to the extrapolation of the outer surface brightness distribution. Depleted cores mainly occur in very luminous, slow rotator galaxies and are thought to result from 'dry merger' events of galaxies hosting black holes. During the galaxy collision the MBHs migrate to the centre of the merger remnant through dynamical friction and form a MBH binary. Stars in the vicinity of the MBH binary are ejected from the nuclear region of the galaxy and depleted galaxy cores form. A kinematical prediction of the MBH binary core scouring scenario is that the orbital distribution in the vicinity of the remnant MBH will be 'tangentially anisotropic',which was observationally confirmed for a number of galaxies. I will present here our kinematical and dynamical study of 20 nearby galaxies (half “cores”, half 'coreless') in which we have tested the scenario above. For our measurements we made wide use of IFU data, such as SINFONI, NIFS, MUSE and more, as well as testing different dynamical measurement methods to derive the MBH masses and the orbital distributions in the vicinity of the central black holes. Among other findings, we do not find more tangential orbits within the sphere of influence of the black holes for cored than for coreless galaxies. I will discuss the implications of this finding and what additional observational data is needed to dynamically detect MBH binaries. I will conclude with a discussion on how we can use the detailed orbital information of dynamical models to get additional information of the build-up of galaxy centers.

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