Molecular Gas in NUclei of GAlaxies (NUGA): II. The Ringed LINER NGC7217

TL;DR

This study uses high-resolution CO maps and N-body simulations to analyze the structure, star formation, and gas dynamics of the nuclear ring in the LINER galaxy NGC7217, revealing the relationship between gas density gradients and star formation activity.

Contribution

It provides detailed CO observations of NGC7217's nuclear ring and introduces N-body simulations that incorporate gas dissipation and star formation to interpret the galaxy's nuclear structure.

Findings

The nuclear ring has a sharp surface density gradient at its inner edge.

Star formation is more intense at the inner edge of the CO ring.

Simulations suggest the galaxy's gas content was higher in the recent past.

Abstract

We present CO(1-0) and CO(2-1) maps of the LINER galaxy NGC7217, obtained with the IRAM interferometer, at 2.4"x1.9" and 1.2"x0.8" resolution respectively. The nuclear ring (at r=12"=0.8kpc) dominates the CO maps, and has a remarkable sharp surface density gradient at its inner edge. The latter is the site of the stellar/Halpha ring, while the CO emission ring extends farther or is broader (500-600pc). This means that the star formation has been more intense toward the inner edge of the CO ring, in a thin layer, just at the location of the high gas density gradient. In the CO(2-1) map, a central concentration inside 3" coincides with a spiral dust lane, clearly seen in the HST V-I color image. N-body simulations including gas dissipation and star formation are performed to better understand the nature of the nuclear ring observed. In the best model, the gas content was higher in the recent past (having been consumed via star formation), and the oval/spiral formed were more self-gravitating (abridged).