Invited review to appear in "Gas Accretion onto Galaxies", Astrophysics and Space Science Library, eds. A. J. Fox & R. Dave.
https://arxiv.org/abs/1612.00774

For a PDF version of the article, click here.

Abstract: While there is no lack of evidence for the accretion of stellar systems onto nearby galaxies, direct evidence for the accretion of gas without stars is scarce. Here we consider an inventory of starless gas “clouds” in and around galaxies of the Local Group to discern their general properties and see how they might appear in distant systems. The conclusion is that accreting gas without stars is detected almost entirely within the circumgalactic medium of large galaxies and is rare otherwise. If our Local Group is any example, the best place to detect starless gas clouds is relatively close to galaxies.

Table of Contents

• GALAXIES THEN AND NOW
• THE DISK-HALO INTERFACE: CLOUDS AND SHELLS
• HIGH VELOCITY CLOUDS
• High Velocity Clouds in M31 and M33
• The Smith Cloud - Accretion in Action
• H I OUTSIDE LOCAL GROUP GALAXIES
• OTHER NEUTRAL GAS IN THE LOCAL GROUP
• IC 10
• M31-M33 Clouds
• STARLESS H I NEAR AND FAR
• REFERENCES

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