2015ApJ...799..234F

In recent observations by the Hubble Space Telescope (HST) as part of a campaign to discover locations and kinematics of AGN outflows, we found that Mrk 509 contains a 3'' (∼2100 pc) linear filament in its central region. Visible in both optical continuum and [O III] imaging, this feature resembles a "check mark" of several knots of emission that travel northwest to southeast before jutting toward the nucleus from the southwest. Space Telescope Imaging Spectrograph (STIS/HST) observations along the inner portion of the filament reveal redshifted velocities, indicating that the filament is inflowing. We present further observations of the nucleus in Mrk 509 using the Gemini Near-Infrared Integral Field Spectrograph, from which we conclude that this structure cannot be related to previously studied, typical narrow line region outflows and instead embodies the remains of an ongoing minor merger with a gas-rich dwarf galaxy, therefore providing a great opportunity to study the fueling of an AGN by a minor merger in progress.