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

TL;DR

This paper uses simulations to show how large-scale environments influence the angular momentum of circumgalactic gas, triggering episodic star formation cycles in galaxies.

Contribution

It demonstrates the role of large-scale environment in modulating CGM angular momentum and star formation activity in galaxies, highlighting a pulsating gas motion cycle.

Findings

Large-scale environment triggers episodic star formation.

Circumgalactic gas exhibits synchronized 'breathing' motions.

Galaxy star formation cycles are linked to CGM angular momentum modulations.

Abstract

The connection between halo gas acquisition through the circumgalactic medium (CGM) and galaxy star formation has long been studied. In this series of two papers, we put this interplay within the context of the galaxy environment on large scales (several hundreds of kpc), which, to a certain degree, maps out various paths for galaxy interactions. We use the IllustrisTNG-100 simulation to demonstrate that the large-scale environment modulates the circumgalactic gas angular momentum, resulting in either enhanced (Paper I) or suppressed (Paper II) star formation inside a galaxy. In this paper (Paper I), we show that the large-scale environment around a star-forming galaxy is often responsible for triggering new episodes of star formation. Such an episodic star formation pattern is well synced with a pulsating motion of the circumgalactic gas, which, on the one hand receives angular momentum modulations from the large-scale environment, yielding in-spiralling gas to fuel the star-forming reservoir, while, on the other hand, is affected by the feedback activities from the galaxy centre. As a result, a present-day star-forming galaxy may have gone through several cycles of star-forming and quiescent phases during its evolutionary history, with the circumgalactic gas carrying out a synchronized cadence of "breathing in and out" motions out to $\sim 100$ kpc.