Published in "Gas Accretion onto Galaxies", Astrophysics and Space Science Library, Volume 430. ISBN 978-3-319-52511-2. Springer International Publishing AG, 2017, p. 355.
https://arxiv.org/abs/1612.00740

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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_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.

Table of Contents

• GAS ACCRETION IN THE CONTEXT OF GALAXY EVOLUTION
• DETECTING GAS ACCRETION
• Observational and Technological breakthroughs
• Measuring the Gas Accretion Rate
• GAS ACCRETION FROM IFU SURVEYS
• Case Study 1: HE2243 at z = 2.32
• Case Study 2: J1422 at z = 0.91
• Metallicity aspects
• Case Study 3: H I selection
• Case Study 3: H I selection
• FUTURE PERSPECTIVES
• REFERENCES