Status of HI searches for CHVCs beyond the Local Group

Abstract

Growing evidence supports the suggestion that the compact high-velocity clouds of HI (CHVCs) are located throughout the Local Group and continue to fuel galactic evolution. Recent distance estimates to individual objects lie in the range 150-850 kpc, implying an HI mass range of 10^5.7 to 10^7.2 M_Sun together with sizes ranging from 2-12 kpc, while the average linewidth is 30 km/s FWHM. It is natural to ask whether objects of this type would not already have been seen by current blind HI surveys of the extragalactic sky. We consider the properties of the deepest published surveys of this type and conclude that the sensitivity and coverage have now begun to reveal the high mass end of the distribution (M_HI >10^7 M_Sun). Achieving detection limits an order of magnitude deeper should finally enable direct study of these systems beyond the Local Group, or definitively rule out their existence.

8 pages, accepted in A&A, major changes and extensions over earlier version

References in corpus (4)

• A confirmed location in the Galactic halo for the high-velocity cloud 'chain A'
• An Extragalactic HI Cloud with No Optical Counterpart?
• The Space Density of Primordial Gas Clouds near Galaxies and Groups and their Relation to Galactic HVCs
• Arecibo imaging of compact high-velocity clouds

Cited by in corpus (14)

• The Progenitors of Dwarf Spheroidal Galaxies
• On the Continuing Formation of the Andromeda Galaxy: Detection of HI Clouds in the M31 Halo
• Complex C: A Low-Metallicity High-Velocity Cloud Plunging into the Milky Way
• Westerbork HI observations of high-velocity clouds near M31 and M33
• A Catalog of Ultra-compact High Velocity Clouds from the ALFALFA Survey: Local Group Galaxy Candidates?
• An all-sky study of compact, isolated high-velocity clouds
• Where are the High Velocity Clouds in Local Group Analogs?
• C II Radiative Cooling of the Diffuse Gas in the Milky Way
• Relics of structure formation: extra-planar gas and high-velocity clouds around the Andromeda Galaxy
• An HI survey of the Centaurus and Sculptor Groups - Constraints on the space density of low mass galaxies
• The NGC 672 and NGC 784 Galaxy Groups: Evidence for Galaxy Formation and Growth Along a Nearby Dark Matter Filament
• A Search for Stellar Populations in High Velocity Clouds
• High Velocity Cloud Edges and Mini-HVCs
• The Far Ultraviolet Spectroscopic picture of the Missing Baryons in the Local Group