Superwind-driven Intense H${}_2$ Emission in NGC 6240 II: Detailed Comparison of Kinematical and Morphological Structures of the Warm and Cold Molecular Gas

Abstract

We report on our new analysis of the spatial and kinematical distribution of warm and cold molecular gas in NGC 6240, which was undertaken to explore the origin of its unusually luminous H${}_2$ emission. By comparing three-dimensional emission-line data (in space and velocity) of CO (J=2-1) in the radio and H${}_2$ in the near infrared, we are able to study the H${}_2$ emitting efficiency, defined in terms of the intensity ratio of H${}_2$ to CO [$I$(H${}_2$)/$I$(CO)], as a function of velocity. The integrated H${}_2$ emitting efficiency is calculated by integrating the velocity profile of H${}_2$ emitting efficiency in blue, red, and total (blue + red) velocity regions of the profile. We find that (1) both the total H${}_2$ emitting efficiency and the blue-to-red ratio of the efficiency are larger in regions surrounding the CO and H${}_2$ intensity peaks, and (2) the H${}_2$ emitting efficiency and the kinematical conditions in the warm molecular gas are closely related to each other. A collision between the molecular gas concentration and the external superwind outflow from the southern nucleus seems plausible to explain these characteristics, since it can reproduce the enhanced emitting efficiency of blueshifted H${}_2$ around the molecular gas concentration, if we assume that the superwind blows from the southern nucleus toward us, hitting the entire gas concentration from behind. In this model, internal cloud-cloud collisions within the molecular gas concentration are enhanced by the interaction with the superwind outflow, and efficient and intense shock-excited H${}_2$ emission is expected as a result of the cloud-crushing mechanism.

12 pages, 6 figures, accepted for publication in AJ

References in corpus (1)

• Formation of gas disks in merging galaxies

Cited by in corpus (16)

• Galactic Winds
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• The Core of NGC 6240 from Keck Adaptive Optics and HST NICMOS Observations
• NGC6240: extended CO structures and their association with shocked gas
• High resolution mapping of CO(1-0) in NGC6240
• The Exceptional Soft X-ray Halo of the Galaxy Merger NGC 6240
• Dense and Warm Molecular Gas between Double Nuclei of the Luminous Infrared Galaxy NGC 6240
• Giant H$\alpha$ nebula surrounding the starburst merger NGC 6240
• Nucler star formation in NGC 6240
• Imaging the Molecular Outflows of the Prototypical ULIRG NGC 6240 with ALMA
• Nuclear absorption and emission in the AGN merger NGC 6240: the hard X-ray view
• PdBI U/LIRG Survey (PULS): Dense Molecular Gas in Arp 220 and NGC 6240
• Tracing the Ionization Structure of the Shocked Filaments of NGC 6240
• The JWST/NIRSpec view of the nuclear region in the prototypical merging galaxy NGC 6240
• Outflowing shocked gas dominates the NIR H${}_2$ emission from the dual AGN NGC6240