Observations of cold gas and star formation in dwarf S0 galaxies

TL;DR

This study investigates star formation in dwarf S0 galaxies using optical and millimetre observations, revealing that they follow the Kennicutt-Schmidt law, have significant rotation, and contain abundant atomic hydrogen, despite irregular kinematics.

Contribution

First detailed analysis of star formation and gas properties in dwarf S0 galaxies, highlighting their rotation, gas composition, and star formation laws in field environments.

Findings

Dwarf S0 galaxies follow the Kennicutt-Schmidt law.

They exhibit irregular stellar and gas velocity fields.

Atomic gas mass is much higher than molecular gas mass.

Abstract

Very little work has been done on star formation in dwarf lenticular galaxies (S0s). We present 2D-spectroscopic and millimetre observations made by Centro Astronomico Hispano Aleman (CAHA) 3.5 m optical and the IRAM-30 m millimetre telescopes, respectively, for a sample of four dwarf S0 galaxies with multiple star formation regions in the field environment. We find that although most of the sources deviate from the star forming main sequence relation, they all follow the Kennicutt-Schmidt law. After comparing the stellar and Halpha kinematics, we find that the velocity fields of both stars and ionized gas do not show regular motion and the velocity dispersions of stars and ionized gas are low in the regions with high star formation, suggesting these star-forming S0 galaxies still have significant rotation. This view can be supported by the result that most of these dwarf S0 galaxies are classified as fast rotators. The ratio of average atomic gas mass to stellar mass (~ 47%) is much greater than that of molecular gas mass to stellar mass (~ 1%). In addition, the gas-phase metallicities in the star-forming regions are lower than that of the non-star-forming regions. These results indicate that the extended star formation may originate from the combination of abundant atomic hydrogen, long dynamic time scale and low-density environment.