Hydrodynamic Shielding and the Survival of Cold Streams

Abstract

Cold clouds in hot media are quickly crushed, shredded, and then accelerated as a result of their interaction with the background gas. The persistence of cold clouds moving at substantial velocities in harsh environments is a common yet puzzling feature of many astrophysical systems, from quasar absorption lines probing galactic halos to clouds of dust passing near Sgr $A^{\ast }$. Here we run a set of idealized numerical experiments, subjecting a line of cold clouds at a series of mutual separations to a hot background wind. We find that this stream of clouds is able to shield itself from hydrodynamic destruction by accelerating the hot background material, creating a protective layer of co-moving gas. We write down a simple diffusion equation that reproduces the behavior of the simulations, and we discuss the implications for cosmological gas accretion and G2.

Submitted to AAS Journals, comments welcome

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Cited by in corpus (14)

• The Impact of Enhanced Halo Resolution on the Simulated Circumgalactic Medium
• The Structure of Multiphase Galactic Winds
• Interaction of a cold cloud with a hot wind: the regimes of cloud growth and destruction and the impact of magnetic fields
• The Diversity and Variability of Star Formation Histories in Models of Galaxy Evolution
• Survival and mass growth of cold gas in a turbulent, multiphase medium
• First results from SMAUG: Uncovering the Origin of the Multiphase Circumgalactic Medium with a Comparative Analysis of Idealized and Cosmological Simulations
• Shock-multicloud interactions in galactic outflows -- II. Radiative fractal clouds and cold gas thermodynamics
• Shock-multicloud interactions in galactic outflows -- I. Cloud layers with log-normal density distributions
• Mass, Morphing, Metallicities: The Evolution of Infalling High Velocity Clouds
• Entrainment of Hot Gas into Cold Streams: The Origin of Excessive Star-formation Rates at Cosmic Noon
• S0-2 star, G1- and G2-objects and flaring activity of the Milky Way's Galactic Center black hole in 2019
• Galactic Superbubbles in 3D: Wind Formation and Cloud Shielding
• Star formation in the circumgalactic high-velocity cloud Complex H
• Multi-cloud crushing -- the collective survival of cold clouds in galactic outflows