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Related papers: All-sky census of Galactic high-latitude molecular…

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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,…

Astrophysics of Galaxies · Physics 2015-05-28 Kyujin Kwak , David B. Henley , Robin L. Shelton

The nucleus of the Milky Way is known to drive a large-scale, multiphase galactic outflow, with gas phases ranging from the hot highly-ionized to the cold molecular component. In this work, we present the first systematic search for…

High velocity gas that does not conform to Galactic rotation is observed throughout the Galaxy's halo. One component of this gas, HI high velocity clouds (HVCs), have attracted attention since their discovery in the 1960s and remain…

Astrophysics of Galaxies · Physics 2017-08-24 Asger Grønnow , Thor Tepper-García , Joss Bland-Hawthorn , Naomi McClure-Griffiths

High-velocity clouds (HVCs) are clouds of HI seen around the Milky Way with velocities inconsistent with Galactic rotation, have unknown distances and masses and controversial origins. One possibility is that HVCs are associated with the…

Using data from the Galactic All-Sky Survey, we have compared the properties and distribution of HI clouds in the disk-halo transition at the tangent points in mirror-symmetric regions of the first quadrant (QI) and fourth quadrant (QIV) of…

Astrophysics of Galaxies · Physics 2015-03-17 H. Alyson Ford , Felix J. Lockman , N. M. McClure-Griffiths

In the spectra of 139 early-type Large Magellanic Cloud (LMC) stars observed with FUSE and with deep radio Parkes HI 21-cm observations along those stars, we search for and analyze the absorption and emission from high-velocity gas at…

Astrophysics of Galaxies · Physics 2009-08-24 N. Lehner , L. Staveley-Smith , J. C. Howk

In the Galactic fountain scenario, supernovae and/or stellar winds propel material into the Galactic halo. As the material cools, it condenses into clouds. By using FLASH three-dimensional magnetohydrodynamic simulations, we model and study…

Astrophysics of Galaxies · Physics 2014-11-20 Kyujin Kwak , Robin L. Shelton , Elizabeth A. Raley

Galactic high-velocity clouds (HVCs) are known to be complex, multiphase systems consisting of neutral and/or ionized gas moving at high velocities relative to the rotation of the disk. In this work, we investigate Milky Way-like galaxies…

Astrophysics of Galaxies · Physics 2025-07-28 Scott Lucchini , Jiwon Jesse Han , Lars Hernquist , Charlie Conroy , Andrew J. Fox

High-velocity clouds (HVCs) are multi-phase gas structures whose velocities (|v_LSR|>100 km/s) are too high to be explained by Galactic disk rotation. While large HVCs are well characterized, compact and small HVCs (with HI angular sizes of…

From our position embedded within the Milky Way's interstellar medium (ISM), we have limited ability to detect gas at low relative velocities in the extended Galactic halo because those spectral lines are blended with much stronger signals…

Astrophysics of Galaxies · Physics 2021-05-21 Hannah V. Bish , Jessica K. Werk , Joshua Peek , Yong Zheng , Mary Putman

The origin of our Galaxy's high-velocity clouds (HVCs) remains a mystery after many decades of effort. In this paper, we use the TNG50 simulation of the IllustrisTNG project to identify cool, dense clouds that match observations of Galactic…

Astrophysics of Galaxies · Physics 2024-10-21 Scott Lucchini , Jiwon Jesse Han , Lars Hernquist , Charlie Conroy

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…

Astrophysics · Physics 2007-05-23 Kenneth R. Sembach , Blair D. Savage , Limin Lu , Edward M. Murphy

We aim at analysing systematically the distribution and physical properties of neutral and mildly ionised gas in the Milky Way halo, based on a large absorption-selected data set. Multi-wavelength studies were performed combining optical…

Astrophysics of Galaxies · Physics 2015-06-04 N. Ben Bekhti , B. Winkel , P. Richter , J. Kerp , U. Klein , M. T. Murphy

We report an observational study of the giant molecular cloud (GMC) associated with the Galactic infrared ring-like structure N35 and two nearby HII regions G024.392+00.072 (HII region A) and G024.510-00.060 (HII region B), using the new CO…

We address the spatial scale, ionization structure, mass and metal content of gas at the Milky Way disk-halo interface detected as absorption in the foreground of seven closely-spaced, high-latitude halo blue horizontal branch stars (BHBs)…

I summarize Far Ultraviolet Spectroscopic Explorer (FUSE) observations of interstellar O VI absorption towards 12 early-type stars in the Large Magellanic Cloud (LMC), the closest disk galaxy to the Milky Way. LMC O VI is seen towards all…

Astrophysics · Physics 2007-05-23 J. Christopher Howk

We present a novel absorption line survey using 54 blue horizontal branch stars (BHBs) in the Milky Way halo as background sources for detecting gas flows at the disk-halo interface. Distance measurements to high-latitude ($b$ > 60{\deg})…

We explore theoretical models of the ionization ratios of the Li-like absorbers NV, OVI, and CIV, in the Galactic halo. These ions are believed to form in nonequilibrium processes such as shocks, evaporative interfaces, or rapidly cooling…

Astrophysics · Physics 2009-11-10 Remy Indebetouw , J. Michael Shull

In the Galactic halo, metal-bearing Galactic halo material mixes into high velocity clouds (HVCs) as they hydrodynamically interact. This interaction begins long before the clouds completely dissipate and long before they slow to the…

Astrophysics of Galaxies · Physics 2014-11-19 Jeffrey A. Gritton , Robin L. Shelton , Kyujin Kwak

The results of the interaction between the Milky Way and the Magellanic Clouds are revealed through several high velocity complexes which are connected to the Clouds. The exact mechanism of their formation is under some debate, but they…

Astrophysics · Physics 2007-05-23 M. E. Putman