Mass, Morphing, Metallicities: The Evolution of Infalling High Velocity Clouds

Abstract

We revisit the reliability of metallicity estimates of high velocity clouds with the help of hydrodynamical simulations. We quantify the effect of accretion and viewing angle on metallicity estimates derived from absorption lines. Model parameters are chosen to provide strong lower limits on cloud contamination by ambient gas. Consistent with previous results, a cloud traveling through a stratified halo is contaminated by ambient material to the point that <10% of its mass in neutral hydrogen consists of original cloud material. Contamination progresses nearly linearly with time, and it increases from head to tail. Therefore, metallicity estimates will depend on the evolutionary state of the cloud, and on position. While metallicities change with time by more than a factor of 10, well beyond observational uncertainties, most lines-of-sight range only within those uncertainties at any given time over all positions. Metallicity estimates vary with the cloud's inclination angle within observational uncertainties. The cloud survives the infall through the halo because ambient gas continuously condenses and cools in the cloud's wake and thus appears in the neutral phase. Therefore, the cloud observed at any fixed time is not a well-defined structure across time, since material gets constantly replaced. The thermal phases of the cloud are largely determined by the ambient pressure. Internal cloud dynamics evolve from drag gradients caused by shear instabilities, to complex patterns due to ram-pressure shielding, leading to a peloton effect, in which initially lagging gas can catch up to and even overtake the head of the cloud.

arXiv comment18 pages, 10 figures. Revised submission to MNRAS

References in corpus (80)

• The Interstellar Environment of our Galaxy
• Athena: A New Code for Astrophysical MHD
• Enzo: An Adaptive Mesh Refinement Code for Astrophysics
• Gaseous Galaxy Halos
• Starburst-driven galactic winds: I. Energetics and intrinsic X-ray emission
• A huge reservoir of ionized gas around the Milky Way: Accounting for the Missing Mass?
• Constraining the Milky Way's Hot Gas Halo with OVII and OVII Emission Lines
• The Structure of the Milky Way's Hot Gas Halo
• Magnetized Gas Clouds can Survive Acceleration by a Hot Wind
• Launching cosmic-ray-driven outflows from the magnetized interstellar medium
• HIPASS High-Velocity Clouds: Properties of the Compact and Extended Populations
• Starburst-Driven Galactic Winds: Filament Formation and Emission Processes
• H_alpha Emission from High-Velocity Clouds and their Distances
• The Magnetic Rayleigh-Taylor Instability in Three Dimensions
• How cold gas continuously entrains mass and momentum from a hot wind
• The survival of gas clouds in the Circumgalactic Medium of Milky Way-like galaxies
• A Reservoir of Ionized Gas in the Galactic Halo to Sustain Star Formation in the Milky Way
• Distances to Galactic high-velocity clouds. Complex C
• Complex C: A Low-Metallicity High-Velocity Cloud Plunging into the Milky Way
• The Fate of High-Velocity Clouds: Warm or Cold Cosmic Rain?
• An Accurate Distance to High-Velocity Cloud Complex C
• Highly Ionized Gas Surrounding High Velocity Cloud Complex C
• Efficiency of gas cooling and accretion at the disc-corona interface
• The Diversity of High- and Intermediate-Velocity Clouds: Complex C versus IV Arch
• The 21-SPONGE HI Absorption Line Survey II: The temperature of Galactic HI
• The Launching of Cold Clouds by Galaxy Outflows II: The Role of Thermal Conduction
• A Large Reservoir of Ionized Gas in the Galactic Halo: Ionized Silicon in High-Velocity and Intermediate-Velocity Clouds
• Smith's Cloud: A High-velocity Cloud Colliding with the Milky Way
• The Magnetohydrodynamics of Shock-Cloud Interaction in Three Dimensions
• The Smith Cloud: HI associated with the Sgr dwarf?
• The Temperature Distribution in Turbulent Interstellar Gas
• Exploring the Origin and Fate of the Magellanic Stream with Ultraviolet and Optical Absorption
• Where are the high velocity clouds?
• The mode of gas accretion onto star-forming galaxies
• A Survey of FUSE and HST Sightlines through High-Velocity Cloud Complex C
• The COS/UVES Absorption Survey of the Magellanic Stream: II. Evidence for a complex enrichment history of the Stream from the Fairall 9 sightline
• High Velocity Rain: The Terminal Velocity of Model of Galactic Infall
• Numerical Study of Turbulent Mixing Layers with Non-Equilibrium Ionization Calculations
• Blowing in the Milky Way wind: neutral hydrogen clouds tracing the Galactic nuclear outflow
• The impact of magnetic fields on thermal instability
• The origin of the high-velocity cloud complex C
• Metallicity and Ionization in High Velocity Cloud Complex C
• HI spectra and column densities toward HVC and IVC probes
• ROHSA: Regularized Optimization for Hyper-Spectral Analysis - Application to phase separation of 21 cm data
• Simulations of High-Velocity Clouds. I. Hydrodynamics and High-Velocity High Ions
• The survival of interstellar clouds against Kelvin-Helmholtz instabilities
• On the Metallicity and Origin of the Smith High-Velocity Cloud
• The evolution of interstellar clouds in a streaming hot plasma including heat conduction
• Deep H I observations of the compact high-velocity cloud HVC125+41-207
• Reconstructing Deconstruction: High-Velocity Cloud Distance Through Disruption Morphology
• Magnetic fields in the Galactic halo restrict fountain-driven recycling and accretion
• Measuring turbulence in the ISM by comparing N(HI;Lya) and N(HI;21cm)
• Metal-Ion Absorption in Conductively Evaporating Clouds
• A Far Ultraviolet Spectroscopic Explorer Survey of Interstellar Molecular Hydrogen in the Galactic Disk
• Accretion of the Magellanic system onto the Galaxy
• The turbulent destruction of clouds - III. Three dimensional adiabatic shock-cloud simulations
• Hubble-COS Observations of Galactic High-Velocity Clouds: Four AGN Sight Lines through Complex C
• The Smith Cloud: high-velocity accretion and dark-matter confinement
• Observation of Acceleration of HI Clouds Within the Fermi Bubbles
• The Smith Cloud and its dark matter halo: Survival of a Galactic disc passage
• MHD Turbulent Mixing Layers: Equilibrium Cooling Models
• Time-Dependent Cooling in Photoionized Plasma
• Gas Accretion onto the Milky Way
• Evaporation and condensation of spherical interstellar clouds. Self-consistent models with saturated heat conduction and cooling
• Starburst Driven Galactic Superbubbles Radiating to 10 K
• Magnetized High Velocity Clouds in the Galactic Halo: A New Distance Constraint
• Collisions between Dark Matter Confined High Velocity Clouds and Magnetized Galactic Disks: The Smith Cloud
• Mixing between High Velocity Clouds and the Galactic Halo
• Si iv Column Densities Predicted from Non-Equilibrium Ionization Simulations of Turbulent Mixing Layers and High-Velocity Clouds
• Efficiency of Thermal Conduction in a Magnetised Circumgalactic Medium
• Physical effects on compact high-velocity clouds in the circumgalactic medium
• Hydrodynamic Shielding and the Survival of Cold Streams
• Chemical enrichment of the pre-solar cloud by supernova dust grains
• MHD Stability of ISM Phase Transition Layers I: Magnetic Field Orthogonal to Front
• The Warm Gas in the MW: A Kinematical Model
• The Effect of Mixing on the Observed Metallicity of the Smith Cloud
• Three-Dimensional Orientation of Compact High Velocity Clouds
• Is the Milky Way's Hot Halo Convectively Unstable?
• A systematic comparison of two-equation RANS turbulence models applied to shock-cloud interactions
• Gas Inflow and Star Formation near Supermassive Black Holes: The Role of Nuclear Activity

Cited by in corpus (15)

• Abundance and temperature of the outer hot circum-Galactic medium: The SRG/eROSITA view of the soft X-ray background in the eFEDS field
• Cloudy with A Chance of Rain: Accretion Braking of Cold Clouds
• About Metallicity Variations in the Local Galactic Interstellar Medium
• Magnetic field draping around clumpy high-velocity clouds in galactic halo
• The role of the halo magnetic field on accretion through High-Velocity Clouds
• Detection of Dust in High-Velocity Cloud Complex C -- Enriched Gas Accreting onto the Milky Way
• Caught in the Act: A Metal-Rich High-Velocity Cloud in the Inner Galaxy
• The high-velocity clouds above the disk of the outer Milky Way: misty precipitating gas in a region roiled by stellar streams
• R-process Rain from Binary Neutron Star Mergers in the Galactic Halo
• Strength in numbers: A multiphase wind model with multiple cloud populations
• On the Origin of High-velocity Clouds in the Galaxy
• A Component of the Smith High Velocity Cloud Now Crossing the Galactic Plane
• Star formation in the circumgalactic high-velocity cloud Complex H
• Neural Infalling Cloud Equations (NICE): Increasing the Efficacy of Subgrid Models and Scientific Equation Discovery using Neural ODEs and Symbolic Regression
• Simulating High-Velocity Clouds in the Observational Plane: An Initial Study with the Smith Cloud