Gas Accretion and Star-Formation Rates with IFUs and Background Quasars

TL;DR

This paper reviews observational techniques using background quasars and IFUs to detect and study gas accretion onto star-forming galaxies, providing evidence for how galaxies sustain star formation.

Contribution

It presents a comprehensive review of the method combining background quasars and IFUs to observe gas accretion in star-forming galaxies, highlighting recent observational evidence.

Findings

Evidence of co-rotating gas structures within 10-30 kpc of galaxies.

Detection of gas inflows consistent with theoretical accretion models.

Enhanced understanding of how gas accretion sustains star formation.

Abstract

Star-forming galaxies (SFGs) are forming stars at a regular pace, forming the so-called main sequence (MS). However, all studies of their gas content show that their gas reservoir ought to be depleted in 0.5-2 Gyr. Thus, SFGs are thought to be fed by the continuous accretion of intergalactic gas in order to sustain their star-formation activity. However, direct observational evidence for this accretion phenomenon has been elusive. Theoretically, the accreted gas coming from the intergalactic medium is expected to orbit about the halo, delivering not just fuel for star-formation but also angular momentum to the galaxy. This accreting material is thus expected to form a gaseous structure that should be co-rotating with the host once at $r<0.3\;R_{\rm vir}$ or $r<10-30$ kpc. Because of the rough alignment between the star-forming disk and this extended gaseous structure, the accreting material can be most easily detected with the combination of background quasars and integral field units (IFUs). In this chapter, accretion studies using this technique are reviewed.