Molecular gas in NUclei of GAlaxies (NUGA) VII. NGC4569, a large scale bar funnelling gas into the nuclear region

TL;DR

This study investigates how a large-scale stellar bar in galaxy NGC4569 channels molecular gas into its nucleus, revealing the dynamics and inflow mechanisms that may fuel nuclear starburst activity.

Contribution

It provides a detailed analysis of molecular gas distribution and kinematics in NGC4569, demonstrating the bar-driven inflow process and identifying the inner Lindblad resonance through advanced modeling.

Findings

70% of molecular gas concentrated within 800 pc

Non-circular motions are comparable to circular motions (~120 km/s)

Gravitational torques funnel gas inside the ILR to 300 pc

Abstract

This work is part of the NUGA survey of CO emission in nearby active galaxies. We present observations of NGC4569, a member of the Virgo Cluster. We analyse the molecular gas distribution and kinematics in the central region and we investigate a possible link to the strong starburst present at the nucleus. 70% of the 1.1x10^9 Msolar of molecular gas detected in the inner 20" is found to be concentrated within the inner 800 pc and is distributed along the large scale stellar bar seen in near-infrared observations. A hole in the CO distribution coincides with the nucleus where most of the Halpha emission and blue light are emitted. The kinematics are modelled in three different ways, ranging from the purely geometrical to the most physical. This approach allows us to constrain progressively the physical properties of the galaxy and eventually to emerge with a reasonable fit to an analytical model of orbits in a barred potential. Fitting an axisymmetric model shows that the non-circular motions must be comparable in amplitude to the circular motions (120 km/s). Fitting a model based on elliptical orbits allows us to identify with confidence the single inner Lindblad resonance (ILR) of the large scale bar. Finally, a model based on analytical solutions for the gas particle orbits in a weakly barred potential constrained by the ILR radius reproduces the observations well. The mass inflow rate is then estimated and discussed based on the best fit model solution. The gravitational torques implied by this model are able to efficiently funnel the gas inside the ILR down to 300 pc, although another mechanism must take over to fuel the nuclear starburst inside 100 pc.