Imaging Carbon Monoxide Emission in the Starburst Galaxy NGC 6000

TL;DR

This study maps CO emissions in NGC 6000's center, revealing a nuclear concentration of gas influenced by a bar potential, and estimates the molecular gas mass and CO-to-H2 conversion factor in this starburst galaxy.

Contribution

First detailed CO emission imaging of NGC 6000's nucleus, linking molecular dynamics to galaxy structure and starburst activity.

Findings

Over 85% of molecular gas is concentrated in the nucleus.

Detected high-velocity dense gas possibly fueling star formation.

Derived a CO-to-H2 conversion factor consistent with other starbursts.

Abstract

We present measurements of carbon monoxide emission in the central region of the nearby starburst NGC 6000 taken with the Submillimeter Array. The J=2-1 transition of 12CO, 13CO, and C18O were imaged at a resolution of ~3''x2'' (450x300 pc). We accurately determine the dynamical center of NGC 6000 at R.A(J2000.0)=15h49m49.5s and dec(J2000.0)=-29d23'13'' which agrees with the peak of molecular emission position. The observed CO dynamics could be explained in the context of the presence of a bar potential affecting the molecular material, likely responsible for the strong nuclear concentration where more than 85% of the gas is located. We detect a kinematically detached component of dense molecular gas at relatively high velocity which might be fueling the star formation. A total nuclear dynamical mass of 7x10^9 Msun is derived and a total mass of gas of 4.6x10^8 Msun, yielding a Mgas/Mdyn~6%, similar to other previously studied barred galaxies with central starbursts. We determined the mass of molecular gas with the optically thin isotopologue C18O and we estimate a CO-to-H2 conversion factor X(CO)=0.4x10^20 cm-2/(K km s-1) in agreement with that determined in other starburst galaxies.