VLBI Observations of NGC6240: resolving the double nuclei and radio supernovae

Abstract

The European VLBI Network (EVN) has been used at two epochs in 2003 and 2009 to obtain multi-frequency high-resolution images of the merger galaxy NGC6240 in order to study the radio properties of all compact high-brightness components in the galaxy. Our observations at milli-arcsecond resolution detected the northern and southern nuclei and two radio components, which we interpret as long-lived luminous supernovae associated with the circum-nuclear starburst activity at the southern nucleus. The new VLBI data support the presence of an active galactic nucleus (AGN) together with starburst activity at the southern nucleus and provides some evidence for an AGN at the northern nucleus. The two nuclei both display an inverted spectrum at lower GHz frequencies. The spectrum of the southern nucleus indicates thermal free-free absorption on parsec scales, consistent with the presence of an AGN.

19 pages, 6 figures, accepted for publication in the Astronomical Journal

References in corpus (6)

• Astrometric accuracy of phase-referenced observations with the VLBA and EVN
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• Serendipitous discovery of the long-sought AGN in Arp 299-A
• Low-luminosity Extragalactic Water Masers toward M82, M51, and NGC4051
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Cited by in corpus (22)

• The subarcsecond mid-infrared view of local active galactic nuclei: I. The N- and Q-band imaging atlas
• ALMA [CI]${}^3{P}_1{-}^3{P}_0$ observations of NGC6240: a puzzling molecular outflow, and the role of outflows in the global ${\alpha }_{\mathrm{CO}}$ factor of (U)LIRGs
• NGC6240: A triple nucleus system in the advanced or final state of merging
• High resolution mapping of CO(1-0) in NGC6240
• NGC6240: extended CO structures and their association with shocked gas
• The Molecular Gas in the NGC 6240 Merging Galaxy System at the Highest Spatial Resolution
• Mass of the Southern Black Hole in NGC 6240 from Laser Guide Star Adaptive Optics
• VLBI studies of DAGN and SMBHB hosting galaxies
• Imaging the Molecular Outflows of the Prototypical ULIRG NGC 6240 with ALMA
• MICONIC: Dual active galactic nuclei, star formation, and ionised gas outflows in NGC 6240 seen with MIRI/JWST
• Nuclear absorption and emission in the AGN merger NGC 6240: the hard X-ray view
• Modelling the Molecular Gas in NGC 6240
• NGC 6240 Supermassive Black Hole Binary dynamical evolution based on Chandra data
• VLBI imaging of the pre-coalescence SMBHB candidate SDSS J143016.05+230344.4
• CON-quest II. Spatially and spectrally resolved HCN/HCO+ line ratios in local luminous and ultraluminous infrared galaxies
• Radio properties of ten nearby ultraluminous infrared galaxies with signatures of luminous buried active galactic nuclei
• Metallicity in the merger Seyfert galaxy NGC 6240
• Molecular Gas in the Nuclear Region of NGC 6240
• High-Resolution Imaging of Water Maser Emission in the active galaxies NGC 6240 and M51
• Dynamical evolution timescales for the triple supermassive black hole system in NGC 6240
• Outflowing shocked gas dominates the NIR H${}_2$ emission from the dual AGN NGC6240
• X-ray and CO-Derived Column Densities in AGN: A Study of Obscuration Properties in CTAGN and Non-CTAGN