Lenticular galaxy IC 719: current building of the counterrotating large-scale stellar disk

TL;DR

This study analyzes the kinematics and composition of the lenticular galaxy IC 719, revealing ongoing star formation in a counterrotating gaseous disk likely fueled by external gas accretion, contributing to the galaxy's disk growth.

Contribution

It provides new evidence of current star formation and external gas accretion in a lenticular galaxy with counterrotating components, highlighting ongoing disk building processes.

Findings

Detection of counterrotating gaseous and stellar components.

Star formation occurring in a ring at 1.4 kpc radius.

Gas metallicity is about half solar abundance.

Abstract

We have obtained and analyzed long-slit spectral data for the lenticular galaxy IC 719. In this gas-rich S0 galaxy, its large-scale gaseous disk counterrotates the global stellar disk. Moreover in the IC 719 disk we have detected a secondary stellar component corotating the ionized gas. By using emission-line intensity ratios, we have proved the gas excitation by young stars and so are claiming current star formation, most intense in a ring-like zone at the radius of 10" (1.4 kpc). The oxygen abundance of the gas in the starforming ring is about half of the solar abundance. Since the stellar disk remains dynamically cool, we conclude that smooth prolonged accretion of the external gas from a neighboring galaxy provides urrent building of the thin large-scale stellar disk.