Molecular Gas in the Nuclear Region of NGC 6240

TL;DR

This study uses high-resolution ALMA observations of CO lines to analyze the molecular gas distribution and kinematics in NGC 6240, revealing a tidal bridge between nuclei and complex gas dynamics affecting galaxy evolution.

Contribution

It provides the first detailed modeling of molecular gas in NGC 6240, showing that a tidal bridge, rather than a disk, best explains the observations.

Findings

Identification of a tidal bridge between nuclei

Detection of high velocity redshifted gas

Poor fit of disk models to the data

Abstract

NGC 6240 is a luminous infrared galaxy in the local universe in the midst of a major merger. We analyze high-resolution interferometric observations of warm molecular gas using CO J = 3 - 2 and 6 - 5 in the central few kpc of NGC 6240 taken by the Atacama Large Millimeter Array. Using these CO line observations, we model the density distribution and kinematics of the molecular gas between the nuclei of the galaxies. Our models suggest that a disk model represents the data poorly. Instead, we argue that the observations are consistent with a tidal bridge between the two nuclei. We also observe high velocity redshifted gas that is not captured by the model. These findings shed light on small-scale processes that can affect galaxy evolution and the corresponding star formation.