The origin of the high-velocity cloud complex C

Abstract

High-velocity clouds consist of cold gas that appears to be raining down from the halo to the disc of the Milky Way. Over the past fifty years, two competing scenarios have attributed their origin either to gas accretion from outside the Galaxy or to circulation of gas from the Galactic disc powered by supernova feedback (galactic fountain). Here we show that both mechanisms are simultaneously at work. We use a new galactic fountain model combined with high-resolution hydrodynamical simulations. We focus on the prototypical cloud complex C and show that it was produced by an explosion that occurred in the Cygnus-Outer spiral arm about 150 million years ago. The ejected material has triggered the condensation of a large portion of the circumgalactic medium and caused its subsequent accretion onto the disc. This fountain-driven cooling of the lower Galactic corona provides the low-metallicity gas required by chemical evolution models of the Milky Way's disc.

6 pages, 4 figures, 1 table; accepted by MNRAS

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Cited by in corpus (24)

• The Circumgalactic Medium
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• A new all-sky map of Galactic high-velocity clouds from the 21-cm HI4PI survey
• Properties of HI discs in the Auriga cosmological simulations
• The Properties of the Circumgalactic Medium in Red and Blue Galaxies: Results from the COS-GASS+COS-Halos Surveys
• Intermediate- and high-velocity clouds in the Milky Way I: covering factors and vertical heights
• Intermediate- and high-velocity clouds in the Milky Way II: evidence for a Galactic fountain with collimated outflows and diffuse inflows
• The Circumgalactic Medium of Milky Way-like Galaxies in the TNG50 Simulation -- II: Cold, Dense Gas Clouds and High-Velocity Cloud Analogs
• The Origin of Exponential Star-forming Disks
• Cool circumgalactic gas of passive galaxies from cosmological inflow
• The Gas-phase Metallicity Profiles of Star-forming Galaxies in the Modified Accretion Disk Framework
• SRG/eROSITA X-ray shadowing study of giant molecular clouds
• Magnetized High Velocity Clouds in the Galactic Halo: A New Distance Constraint
• Efficiency of Thermal Conduction in a Magnetised Circumgalactic Medium
• New Analytic Solutions for Galaxy Evolution II: Wind Recycling, Galactic Fountains and Late-Type Galaxies
• The multifarious ionization sources and disturbed kinematics of extraplanar gas in five low-mass galaxies
• Fountain-driven gas accretion feeding star formation over the disc of NGC 2403
• The effect of rotation on the thermal instability of stratified galactic atmospheres - II. The formation of High Velocity Clouds
• Robust profile decomposition for large extragalactic spectral-line surveys
• Detection of Dust in High-Velocity Cloud Complex C -- Enriched Gas Accreting onto the Milky Way
• Exploring Hydrodynamic Instabilities along the Infalling High-Velocity Cloud Complex A
• Interpreting Observations of Absorption Lines in the Circumgalactic Medium with a Turbulent Medium
• Resolving the formation of cold HI filaments in the high velocity cloud complex C