From large-scale environment to CGM angular momentum to star forming activities -- II: quenched galaxies

TL;DR

This study uses the IllustrisTNG-100 simulation to demonstrate that higher angular momentum in the CGM and large-scale environment correlates with galaxy quenching, affecting gas inflow and star formation activity.

Contribution

It reveals that high CGM angular momentum inherited from the large-scale environment is a key factor in galaxy quenching, extending previous findings to include the role of angular momentum in suppressing star formation.

Findings

Quenched galaxies have higher angular momentum in CGM and environment since z=2.

High CGM angular momentum inhibits gas inflow, leading to quenching.

Observable signatures include coherent rotation patterns and anti-correlation with star formation.

Abstract

The gas needed to sustain star formation in galaxies is supplied by the circumgalactic medium (CGM), which in turn is affected by accretion from large scales. In a series of two papers, we examine the interplay between a galaxy's ambient CGM and central star formation within the context of the large-scale environment. We use the IllustrisTNG-100 simulation to show that the influence exerted by the large-scale galaxy environment on the CGM gas angular momentum results in either enhanced (Paper I) or suppressed (Paper II, this paper) star formation inside a galaxy. We find that for present-day quenched galaxies, both the large-scale environments and the ambient CGM have always had higher angular momenta throughout their evolutionary history since at least $z=2$, in comparison to those around present-day star-forming disk galaxies, resulting in less efficient gas inflow into the central star-forming gas reservoirs. A sufficiently high CGM angular momentum, as inherited from the larger-scale environment, is thus an important factor in keeping a galaxy quenched, once it is quenched. The process above naturally renders two key observational signatures: (1) a coherent rotation pattern existing across multiple distances from the large-scale galaxy environment, to the circumgalactic gas, to the central stellar disk; and (2) an anti-correlation between galaxy star-formation rates and orbital angular momenta of interacting galaxy pairs or groups.