A possible close supermassive black hole binary in a galaxy with precessing outflows of ionized gas.

The study of supermassive black holes (SMBHs) has become a significant effort in the field of Astrophysics recently. The discovery of several black hole scaling relationships, the effects of general relativity revealed in the first image of a SMBH in the galaxy M87, and the prospects of detecting gravitational waves (GWs) from SMBH mergers using laser interferometers, show that SMBHs are not just astronomical ornaments sitting at the centers of galaxies, but they play a crucial role in the formation and evolution of galaxies. In this talk, I will describe recent work showing how SMBHs influence their host galaxies. I will focus on our team’s recent results for a large sample of nearby active SMBHs, also known as active galactic nuclei (AGN), observed with Adaptive Optics (AO) and the integral-field spectrograph OSIRIS at the Keck Observatory. Specifically, I will report on the detection of a possible supermassive black hole binary (SMBHB) with a separation of 0.02 pc in the nearly edge-on galaxy NGC 4388. The tidal interaction between the SMBHB and a circumbinary disk is causing a precessing outflow of highly-ionized gas at scales of ~200 pc and a precession period of ~1.6 Myr. This is the first time that a candidate SMBHB is detected using the two-dimensional (2D) kinematics of the ionized gas in a galaxy, and represents one of the closest-separation SMBHBs studied to date.