Radio Emission Associated with Ultraluminous X-ray Sources in the Galaxy Merger NGC 3256

Abstract

We present new 6, 3.6, and 2 cm VLA radio observations of the nearby merger system NGC 3256, with resolutions of ~100 pc, which reveal compact radio sources embedded in more diffuse emission at all three wavelengths. The two radio nuclei are partially resolved, but the two dominant compact sources that remain coincide with the two most powerful compact Ultraluminous X-ray sources (ULXs) recently reported by Lira et al. The radio/X-ray ratios for these two sources are too high by factors of >100-1000 to be normal X-ray binaries. However, their radio and X-ray powers and ratios are consistent with low-luminosity active galactic nuclei (LLAGNs), and optical emission lines suggest the presence of a nuclear disk around the northern nucleus. If the two nuclear ULXs are LLAGNs, their associated black holes are separated by only \~1kpc, about 6 times closer to one another than those found recently in the merger galaxy NGC 6240. A third ULX on the outskirts of the merger is also a radio source, and probably is a collection of supernova remnants. The remaining ULXs are not coincident with any source of compact radio emission, and are consistent with expectations for beamed X-ray binaries or intermediate-mass black holes.

arXiv commentAccepted for ApJ (10 pages, 5 figures)

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• A Luminous Infrared Merger with Two Bipolar Molecular Outflows: ALMA and SMA Observations of NGC 3256
• Radio Emission from the Intermediate-mass Black Hole in the Globular Cluster G1
• A Supernova Factory in the Merger System Arp 299
• The Effect of Gravitational Recoil on Black Holes Forming in a Hierarchical Universe
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• Imaging Molecular Gas in the Luminous Merger NGC 3256 : Detection of High-Velocity Gas and Twin Gas Peaks in the Double Nucleus
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• ALMA Astrochemical Observations of the Infrared-Luminous Merger NGC 3256
• Outflow of hot and cold molecular gas from the obscured secondary nucleus of NGC3256: closing in on feedback physics
• High spatial resolution T-ReCS mid-infrared imaging of Luminous Infrared Galaxies
• XMM-Newton observations of the starburst merger galaxies NGC 3256 & NGC 3310
• Milliarcsec-scale radio emission of ultraluminous X-ray sources: steady jet emission from an intermediate-mass black hole?
• ALMA observations of HCN and HCO+ outflows in the merging galaxy NGC 3256
• Infrared and X-Ray Evidence of an AGN in the NGC 3256 Southern Nucleus
• The Toomre Sequence Revisited with HST/NICMOS: Nuclear Brightness Profiles and Colors of Interacting and Merging Galaxies
• The nearest extreme starburst: bubbles, young star clusters, and outflow in NGC 3256
• High spatial resolution mid-infrared spectroscopy of the starburst galaxies NGC 3256, IIZw40 and Henize 2-10
• New H2O masers in Seyfert and FIR bright galaxies. III. The Southern Sample
• Star formation traced by optical and millimeter hydrogen recombination lines and free-free emissions in the dusty merging galaxy NGC 3256 -- MUSE/VLT and ALMA synergy
• The Diffuse and Compact X-ray Components of the Starburst Galaxy Henize~2-10
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• Radio Recombination Lines from the Starburst Galaxy NGC 3256
• Dense circum-nuclear molecular gas in starburst galaxies
• Multiwavelength study of the bright X-ray source population in the interacting galaxies NGC5774/NGC5775
• Observed CN and HCN intensity ratios exhibit subtle variations in extreme galaxy environments
• Revealing the nature of the ULX and X-ray population of the spiral galaxy NGC 4088
• JWST reveals the diversity of nuclear obscuring dust in nearby AGN: nuclear isolation of MIRI/MRS datacubes and continuum spectral fitting
• A plausible link between dynamically unsettled molecular gas and the radio jet in NGC 6328