A SINFONI view of Galaxy Centers: Morphology and Kinematics of five Nuclear Star Formation Rings

TL;DR

This study uses near-infrared integral-field spectroscopy to analyze the morphology and kinematics of star formation rings in five nearby spiral galaxies, revealing star-forming regions and proposing a diagnostic for their relative ages.

Contribution

It provides detailed morphological and kinematic maps of nuclear star formation rings and introduces a new emission line ratio diagnostic for assessing star formation hot spot ages.

Findings

Star formation in rings is triggered near dust lane intersections.

The emission line ratio diagnostic indicates hot spot ages.

Star formation occurs predominantly at specific ring regions.

Abstract

We present near-infrared (H- and K-band) integral-field observations of the circumnuclear star formation rings in five nearby spiral galaxies. The data, obtained at the Very Large Telescope with the SINFONI spectrograph, are used to construct maps of various emission lines that reveal the individual star forming regions ("hot spots") delineating the rings. We derive the morphological parameters of the rings, and construct velocity fields of the stars and the emission line gas. We propose a qualitative, but robust, diagnostic for relative hot spot ages based on the intensity ratios of the emission lines Brackett gamma, HeI, and [FeII]. Application of this diagnostic to the data presented here provides tentative support for a scenario in which star formation in the rings is triggered predominantly at two well-defined regions close to, and downstream from, the intersection of dust lanes along the bar with the inner Lindblad resonance.