A Minor Merger Caught In The Act Of Fueling The AGN In Mrk 509

TL;DR

This paper reports the discovery of a filament in Mrk 509 that is inflowing towards the nucleus, likely representing a minor merger with a gas-rich dwarf galaxy fueling the AGN.

Contribution

It provides the first observational evidence of a minor merger actively fueling an AGN in Mrk 509, distinct from typical outflow phenomena.

Findings

The filament shows redshifted velocities indicating inflow.

The structure is unrelated to known NLR outflows.

It is likely a minor merger with a dwarf galaxy.

Abstract

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$''$ ($\sim$2100 {\it pc}) linear filament in its central region. Visible in both optical continuum and [OIII] imaging, this feature resembles a `check mark' of several knots of emission that travel northwest to southeast before jutting towards 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 (NIFS), from which we conclude that this structure cannot be related to previously studied, typical NLR 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.