Inspiralling Supermassive Black Holes: A New Signpost for Galaxy Mergers

Understand

We present a new technique for observationally identifying galaxy mergers spectroscopically rather than through host galaxy imaging.

• Our technique exploits the dynamics of supermassive black holes (SMBHs) powering active galactic nuclei (AGNs) in merger-remnant galaxies.
• Because structure in the universe is built up through galaxy mergers and nearly all galaxies host a central SMBH, some galaxies should possess two SMBHs near their centers as the result of a recent merger.
• These SMBHs spiral to the center of the resultant merger-remnant galaxy, and one or both of the SMBHs may power AGNs.