Related papers: Where are the high velocity clouds?
We use archival UV absorption-line data from HST/STIS to statistically analyse the absorption characteristics of the high-velocity clouds (HVCs) in the Galactic halo towards more than 40 extragalactic background sources. We determine…
Models of hierarchical galaxy formation predict that large numbers of low-mass, dark matter halos remain around galaxies today. These models predict an order of magnitude more halos than observed stellar satellites in the Local Group. One…
Arecibo mapping is reported of the neutral hydrogen distribution along selected directions out from the centers of two small High Velocity Clouds (HVC), W486 and W491. Both HVCs have a small inner region where the neutral hydrogen column…
High--resolution 2D--MHD numerical simulations have been carried out to investigate the effects of continuing infall of clumpy gas in extended HI galactic disks. Given a certain accretion rate, the response of the disk depends on its…
The high-velocity clouds of atomic hydrogen, discovered about 35 years ago, have velocities inconsistent with simple Galactic rotation models that generally fit the stars and gas in the Milky Way disk. Their origins and role in Galactic…
Optical emission lines provide an important new window on the HVCs. Recent studies of the H-alpha line reveal that ionized gas is pervasively associated with the neutral hydrogen in HVCs. The Wisconsin H-Alpha Mapper (WHAM) instrument has…
High-velocity clouds (HVCs) are interstellar clouds of atomic hydrogen that do not partake of the Galactic rotation and have velocities of a several hundred kilometers per second. A considerable number of these clouds are falling down…
The Arecibo HI Strip Survey probed the halos of ~300 cataloged galaxies and the environments of ~14 groups with sensitivity to neutral hydrogen masses > 10^7 M_sun. The survey detected no objects with properties resembling the High Velocity…
High-velocity clouds (HVCs) may fuel future star formation in the Milky Way, but they must first survive their passage through the hot halo. While recent work has improved our understanding of the survival criterion for cloud-wind…
Gas that escapes from the Galactic disk, rises into the halo, cools and falls back, constitutes a "Galactic Fountain". Three-Dimensional simulations show that such a fountain model reproduces many of the features that have been observed in…
The HI in disk galaxies frequently extends beyond the optical image, and can trace the dark matter there. I briefly highlight the history of high spatial resolution HI imaging, the contribution it made to the dark matter problem, and the…
We study the formation of disks via the cooling flow of gas within galactic haloes using smoothed particle hydrodynamics simulations. These simulations resolve mass scales of a few thousand solar masses in the gas component for the first…
Significant numbers of high-velocity HI clouds (HVCs) have now been detected in H-alpha, with a subset seen in low ionization lines (e.g. [NII]). It was originally hoped that the observed H-alpha strength would provide a distance constraint…
Observations of turbulent velocity dispersions in the HI component of galactic disks show a characteristic floor in galaxies with low star formation rates and within individual galaxies the dispersion profiles decline with radius. We carry…
We derived the dust-to-HI ratio of the intermediate-velocity clouds (IVCs), the high-velocity clouds (HVCs), and the local HI gas, by carrying out a multiple-regression analysis of the 21cm HI emission combined with the sub-mm dust optical…
This study developed an automated identification procedure for compact clouds with broad velocity widths in the spectral line data cubes of highly crowded regions. The procedure was applied to the CO J=3-2 line data, obtained using the…
The Milky Way is acquiring gas from infalling high-velocity clouds. The material enters a disk-halo interface that in many places is populated with HI clouds that have been ejected from the disk through processes linked to star formation.…
[Abridged] The interstellar medium is observed to be organised in filamentary structures, as well as neutral (HI) and ionized (HII) bubbles. The expanding nature of these bubbles makes them shape their surroundings and possibly play a role…
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…
We report the results of an extensive FUSE study of high velocity OVI absorption along 102 complete sight lines through the Galactic halo. The high velocity OVI traces a variety of phenomena, including tidal interactions with the Magellanic…