SIMBAD references

The Arecibo H I Strip Survey probed the halos of ∼300 cataloged galaxies and the environments of ∼14 groups with sensitivity to neutral hydrogen masses ≥10⁷ M_☉. The survey detected no objects with properties resembling the high-velocity clouds (HVCs) associated with the Milky Way or Local Group. If the HVCs were typically M_HI_=10^7.5 M_☉ objects distributed throughout groups and galaxy halos at distances of ∼1 Mpc, the survey should have made ∼70 HVC detections in groups and ∼250 detections around galaxies. The null detection implies that HVCs are deployed at typical distances of ≤200 kpc from the galaxies or group barycenters. If the clouds are in virial equilibrium, their average dark matter fraction must be 98% or higher.