NGC6240: A triple nucleus system in the advanced or final state of merging

Abstract

NGC6240 is a well-studied nearby galaxy system in the process of merging. Based on optical, X-ray, and radio observations, it is thought to harbor two active nuclei We carried out a detailed optical 3D spectroscopic study to investigate the inner region of this system in connection with existing MERLIN and VLBA data. We observed NGC6240 with very high spatial resolution using the MUSE instrument in the Narrow-Field Mode with the four-laser GALACSI adaptive optics system on the ESO VLT under seeing conditions of 0.49 arcsec. Our 3D spectra cover the wavelength range from 4725 to 9350 AA at a spatial resolution of ~75 mas. We report the discovery of three nuclei in the final state of merging within a region of only 1 kpc in the NGC6240 system.Thanks to MUSE we are able to show that the formerly unresolved southern component actually consists of two distinct nuclei separated by only 198 pc. In combination with Gaia data we reach an absolute positional accuracy of only 30 mas that is essential to compare optical spectra with MERLIN and VLBA radio positions. The verification and detailed study of a system with three nuclei, two of which are active and each with a mass in excess of $9\times 10^7{M}_{\odot }$, is of great importance for the understanding of hierarchical galaxy formation via merging processes since multiple mergers lead to a faster evolution of massive galaxies in comparison to binary mergers. So far it has been suggested that the formation of galactic nuclei with multiple supermassive black holes (SMBHs) is expected to be rare in the local universe.Triple massive black hole systems might be of fundamental importance for the coalescence of massive black hole binaries in less than a Hubble time leading to the loudest sources of gravitational waves in the millihertz regime.

15 pages, 13 figures, typos corrected, Astronomy & Astrophysics in press

References in corpus (12)

• The Host Galaxies and Classification of Active Galactic Nuclei
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• The MAPPINGS III Library of Fast Radiative Shock Models
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• The Origin of the Magellanic Stream and Its Leading Arm
• Dynamics of triple black hole systems in hierarchically merging massive galaxies
• Buried AGNs in Advanced Mergers:Mid-infrared color selection as a dual AGN finder
• Discovery of a close-separation binary quasar at the heart of a z~0.2 merging galaxy and its implications for low-frequency gravitational waves
• Modelling narrow-line regions of active galaxies in the Sloan Digital Sky Survey - I.Sample selection and physical conditions
• Following Black Hole Scaling Relations Through Gas-Rich Mergers
• Emission Line Galaxies and Active Galactic Nuclei in WINGS clusters
• Radio-Excess IRAS Galaxies: IV. Optical Spectroscopy

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