A plausible link between dynamically unsettled molecular gas and the radio jet in NGC 6328

TL;DR

This study detects and characterizes a jet-induced molecular gas outflow in NGC 6328, linking the outflow to the galaxy's radio jet and suggesting a merger history influences gas dynamics.

Contribution

It provides the first detailed kinematic analysis of jet-induced molecular outflows in NGC 6328 using ALMA data and a novel 3D gas modeling approach.

Findings

Detection of outflowing molecular gas aligned with the radio jet.

Identification of a warped disk structure likely from a past merger.

Quantification of the outflow mass, rate, and kinetic power.

Abstract

We report the detection of outflowing molecular gas at the center of the nearby radio galaxy NGC6328 (z=0.014), which has a gigahertz-peaked spectrum radio core and a compact (2 pc) young double radio lobe tracing jet. Utilizing Atacama Large Millimeter/submillimeter Array (ALMA) CO(2-1) and CO(3-2) observations, as well as a novel code developed to fit the 3D gas distribution and kinematics, to study the molecular gas kinematics, we find that the bulk of the gas is situated within a highly warped disk structure, most likely the result of a past merger event. Our analysis further uncovers, within the inner regions of the gas distribution (R<300 pc) and at a position angle aligning with that of the radio jet (150 degrees), the existence of two anti-diametric molecular gas structures kinematically detached from the main disk. These structures most likely trace a jet-induced cold gas outflow with a total lower limit mass of $2\times 10^6\,\mathrm{M_\odot}$ mass, corresponding to an outflow rate of $2\,\mathrm{M_\odot\,yr^{-1}}$ and a kinetic power of $2.7\times 10^{40}\,\mathrm{erg\,s^{-1}}$. The energy required to maintain such a molecular outflow is aligned with the mechanical power of the jet.