High-velocity clouds

@inproceedings{Wakker1991HighvelocityC,
  title={High-velocity clouds},
  author={Bart P. Wakker},
  year={1991}
}
▪ Abstract High-velocity clouds (HVCs) consist of neutral hydrogen (HI) at velocities incompatible with a simple model of differential galactic rotation; in practice one uses vLSR 90 km/s to define HVCs. This review describes the main features of the sky and velocity distributions, as well as the available information on cloud properties, small-scale structure, velocity structure, and observations other than in 21-cm emission. We show that HVCs contain heavy elements and that the more prominent… Expand
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Do high-velocity clouds form by thermal instability?
We examine the proposal that the H i‘high-velocity’ clouds (HVCs) surrounding the Milky Way and other disc galaxies form by condensation of the hot galactic corona via thermal instability. Under the… Expand
Physical properties of two compact high-velocity clouds possibly associated with the leading arm of the Magellanic system
Aims. We observed two compact high-velocity clouds HVC 291+26+195 and HVC 297+09+253 to analyse their structure, dynamics, and physical parameters. In both cases there is evidence for an association… Expand
Distribution of the high-velocity clouds in the Galactic halo
Context. There is a connection between the kinematics and sky distribution of the high velocity clouds (HVCs) and the spatial velocity and orbital plane of the Magellanic Clouds (MCs) that allow us… Expand
Searching for stars in compact high-velocity clouds – II
ABSTRACT We address the hypothesis that High Velocity Clouds correspond to the “missing”dwarf galaxies of the Local Group predicted by cosmological simulations. To thisend, we present optical and… Expand
Global properties of the HI high velocity sky. A statistical investigation based on the LAB survey
Context. Since 1973, it has been known that some H i high velocity clouds (HVCs) have a core-envelope structure. Recent observations of compact HVCs confirm this, but more general investigations have… Expand
Searching for stars in compact high-velocity clouds – I. First results from VLT and 2MASS
We investigate the hypothesis that compact high-velocity clouds (CHVC) are the 'missing' dwarf galaxies of the Local Group, by searching them for populations of resolved stars. To this end we… Expand
The High-Velocity Gas toward Messier 5: Tracing Feedback Flows in the Inner Galaxy
We present FUSE and STIS E140M observations of the post-AGB star ZNG 1 in the globular cluster Messier 5 ( -->l = 3.9°, -->b = + 47.7°; -->d = 7.5 kpc , -->z = + 5.3 kpc ). High-velocity absorption… Expand
On the Critical Ionization Velocity Effect in Interstellar Space and Possible Detection of Related Continuum Emission
Interstellar neutral hydrogen (HI) emission spectra manifest several families of linewidths whose numerical values (34, 13, and 6 km/s) appear to be related to the critical ionization velocities… Expand
A confirmed location in the Galactic halo for the high-velocity cloud ‘chain A’
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… Expand
Ca II K interstellar observations towards early-type disc and halo stars – distances to intermediate- and high-velocity clouds
We compare existing high spectral resolution (R = λ/Δλ ∼40 000) Ca II K observations (λ air = 3933.66 A) towards 88 mainly B-type stars, and new observations taken using the Intermediate dispersion… Expand
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References

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We present the first complete catalogue of high-velocity clouds (HVCs), followed by a classification of these clouds into complexes and populations. The catalogue will form the basis for comparisons… Expand
Westerbork observations of high-velocity clouds. Discussion
Six high-velocity cloud fields were observed with 1' and 1 km s-1 resolution, using the Westerbork Synthesis Radio Telescope. The structures seen in earlier observations at 10' resolution break up… Expand
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IRAS observations are used to look for infrared emission from dust in high-velocity clouds (HVCs). None of these clouds is detected. The upper limit that can be set on the IR emission per hydrogen… Expand
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High-sensitivity 21 cm observations of the region of the Sculptor group of galaxies reveal at least 30 H I clouds distributed over only the southern sector of the group. These new data add two… Expand
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