Related papers: Arecibo imaging of compact high-velocity clouds

Models that reproduce the observed high-velocity clouds (HVCs) also predict clouds at lower radial velocities that may easily be confused with Galactic disk (|z| < 1 kpc) gas. We describe the first search for these low-velocity halo clouds…

A population of discrete HI clouds in the halo of the inner Galaxy has been discovered in 21cm observations made with the Green Bank Telescope. The halo clouds are seen up to 1.5 kpc from the Galactic plane at many longitudes. Their…

High-velocity clouds (HVC), fast-moving ionized and neutral gas clouds found at high galactic latitudes, may play an important role in the evolution of the Milky Way. The extent of this role depends sensitively on their distances and total…

Observations of W51 with the Submillimeter Wave Astronomy Satellite (SWAS) have yielded the first detection of water vapor in a diffuse molecular cloud. The water vapor lies in a foreground cloud that gives rise to an absorption feature at…

As part of the HI Arecibo Galaxy Environments Survey (AGES) we have observed 5$\times$4 degrees of sky centred on M33, reaching a limiting column density of $\sim 1.5 \times 10^{17}$ cm$^{-2}$ (line width of 10 km s$^{-1}$ and resolution…

Recent spectroscopic observations of intermediate- and high-velocity clouds (IVCs and HVCs) in the Milky Way halo have unveiled the presence of diffuse interstellar molecular hydrogen (H_2) several kpc away from the Galactic disk. Most of…

We present observations of an HI cloud complex most likely located in the Virgo galaxy cluster, first reported by Kent et al. (2007). The complex consists of five clouds, detected in the data set of the ALFALFA extragalactic HI survey at…

The recent detection of a 3.5 keV X-ray line from the centres of galaxies and clusters by Bulbul et al. (2014a) and Boyarsky et al. (2014a) has been interpreted as emission from the decay of 7 keV sterile neutrinos which could make up the…

Most detected neutral atomic hydrogen (HI) at low redshift is associated with optically bright galaxies. However, a handful of HI clouds are known which appear to be optically dark and have no nearby potential progenitor galaxies, making…

We present hydrodynamic simulations of high-velocity clouds (HVCs) traveling through the hot, tenuous medium in the Galactic halo. A suite of models was created using the FLASH hydrodynamics code, sampling various cloud sizes, densities,…

A catalog of Southern anomalous-velocity HI clouds at Decl. < +2 deg is presented, based on data from the HI Parkes All-Sky Survey (HIPASS). The improved sensitivity (5sigma: T_B = 0.04 K) and resolution (15.5') of the HIPASS data results…

High-velocity clouds (HVCs) are interstellar gas clouds whose velocities are incompatible with Galactic rotation. Since the first discovery of HVCs in 1963, their origins have been debated for decades but are still not settled down, because…

The warm neutral medium (WNM) was thought to be subsonically/transonically turbulent, and it lacks a network of intertwined filaments that are commonly seen in both molecular clouds and cold neutral medium (CNM). Here, we report HI~21 cm…

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…

We report ultraviolet spectra of Galactic high-velocity clouds (HVCs) in Complex C, taken by the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), together with new 21-cm spectra from the Green Bank Telescope. The wide…

We present results from multi-epoch neutral hydrogen (HI) absorption observations of six bright pulsars with the Arecibo telescope. Moving through the interstellar medium (ISM) with transverse velocities of 10--150 AU/yr, these pulsars have…

We have recently used the Hubble Space Telescope to study a pair of high velocity clouds in the direction of Mrk 509 that have unusual ionization properties. They exhibit strong CIV absorption with little or no low ion absorption or HI 21cm…

We have identified a class of high-velocity clouds which are compact and apparently isolated. The clouds are compact in that they have angular sizes less than 2 degrees FWHM. They are isolated in that they are separated from neighboring…

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 detect the neutral hydrogen (HI) radial brightness temperature profile in large-scale haloes by stacking 48,430 galaxies selected from the 2dFGRS catalogue onto a set of 21-cm intensity maps obtained with the Parkes radio telescope,…