We present data probing the spatial and kinematical distribution of both the atomic ( H i ) and molecular ( CO ) gas in NGC 5218 , the late-type barred spiral galaxy in the spiral–elliptical interacting pair , Arp 104 .
We consider these data in conjunction with far-infrared and radio continuum data , and N -body simulations , to study the galaxies interactions , and the star formation properties of NGC 5218 .
We use these data to assess the importance of the bar and tidal interaction on the evolution of NGC 5218 , and the extent to which the tidal interaction may have been important in triggering the bar .
The molecular gas distribution of NGC 5218 appears to have been strongly affected by the bar ; the distribution is centrally condensed with a very large surface density in the central region .
The N -body simulations indicate a timescale since perigalacticon of \sim 3 \times 10 ^ { 8 } yr , which is consistent with the interaction having triggered or enhanced the bar potential in NGC 5218 , leading to inflow and the large central molecular gas density observed .
Whilst NGC 5218 appears to be undergoing active star formation , its star formation efficiency is comparable to a ‘ normal ’ SBb galaxy .
We propose that this system may be on the brink of a more active phase of star formation .