Observation of Acceleration of H i Clouds within the Fermi Bubbles

Lockman, Felix J.; Teodoro, Enrico M. Di; McClure-Griffiths, N. M.

doi:10.3847/1538-4357/ab55d8

Cited by 38 publications

(35 citation statements)

References 35 publications

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“…9g). A population of ∼ 200 compact high-velocity HI clouds has been detected within ±1.5 kpc of the Galactic plane, centered on the GC (McClure-Griffiths et al 2013;Di Teodoro et al 2018;Lockman et al 2020). Di have argued that the kinematics of these clouds do not follow Galactic rotation but are instead consistent with a simple GC-centered biconical volume-filling outflow model with a constant radial velocity of ∼ 330 km s −1 and an opening angle > 140 • .…”

Section: Dust Cycle: Formation and Destructionmentioning

confidence: 97%

“…While these numbers may be off by factors of a few, given new evidence of acceleration of these HI clouds (Fig. 9h; Lockman et al 2020), it is clear that this H I outflow is considerably less energetic than that associated with the Fermi Bubbles, and may in principle be driven by a past starburst rather than a recent AGN episode.…”

Section: Dust Cycle: Formation and Destructionmentioning

confidence: 98%

See 1 more Smart Citation

Cool outflows in galaxies and their implications

Veilleux

Maiolino

Bolatto

et al. 2020

Astron Astrophys Rev

421

310

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Neutral-atomic and molecular outflows are a common occurrence in galaxies, near and far. They operate over the full extent of their galaxy hosts, from the innermost regions of galactic nuclei to the outermost reaches of galaxy halos. They carry a substantial amount of material that would otherwise have been used to form new stars. These cool outflows may have a profound impact on the evolution of their host galaxies and environments. This article provides an overview of the basic physics of cool outflows, a comprehensive assessment of the observational techniques and diagnostic tools used to characterize them, a detailed description of the best-studied cases, and a more general discussion of the statistical properties of these outflows in the local and distant universe. The remaining outstanding issues that have not yet been resolved are summarized at the end of the review to inspire new research directions.

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Section: Dust Cycle: Formation and Destructionmentioning

confidence: 97%

Section: Dust Cycle: Formation and Destructionmentioning

confidence: 98%

Cool outflows in galaxies and their implications

Veilleux

Maiolino

Bolatto

et al. 2020

Astron Astrophys Rev

421

310

View full text Add to dashboard Cite

show abstract

“…Our model addresses the evolution and contamination of an infalling cloud, but similar contamination mechanisms might be expected for outflowing clouds driven by Galactic winds (e.g. Di Teodoro et al 2018;Lockman et al 2020). Depending on the balance between ram pressure acceleration by the wind and gravitational acceleration, corresponding models might be closer to wind-tunnel experiments than envisaged here.…”

Section: Discussionmentioning

confidence: 52%

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

Heitsch,

Marchal,

Miville-Deschênes

et al. 2021

Preprint

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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.

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“…Recent 21-cm emission surveys (McClure-Griffiths et al 2013;Di Teodoro et al 2018;Lockman et al 2020) have discovered a large sample of ∼200 neutral hydrogen clouds between ∼0.5-3.5 kpc from the Galactic midplane in the region commonly referred to as the Fermi bubbles (Su et al 2010). Interestingly, molecular gas is observed to be spatially coincident with at least some of these atomic clouds (Di Teodoro et al 2020;Su et al 2021) and similarly for the Small Magellanic Cloud (McClure-Griffiths et al 2018;Di Teodoro et al 2019).…”

Section: Clouds In the Galactic Centermentioning

confidence: 98%

The Survival of Multiphase Dusty Clouds in Hot Winds

Farber,

Gronke

2021

Preprint

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Much progress has been made recently in the acceleration of ∼ 10 4 K clouds to explain absorption-line measurements of the circumgalactic medium and the atomic phase of galactic winds. However, the origin of the molecular phase in galactic winds has received relatively little theoretical attention. Studies of the survival of atomic clouds suggest efficient radiative cooling may enable the survival of expelled material from galactic disks. Alternatively, atomic and molecular gas may form within the outflow, if dust survives the acceleration process. We explore the survival of molecular, dusty clouds in a hot wind with three-dimensional hydrodynamic simulations in which we include radiative cooling and model dust as tracer particles. We find that molecular gas can be destroyed, survive, or transformed entirely to ∼ 10 4 K gas. We establish analytic criteria distinguishing these three outcomes which compare characteristic cooling times to the 'cloud crushing' time of the system. In contrast to typically studied atomic ∼ 10 4 K clouds, molecular clouds are entrained faster than the drag time as a result of efficient mixing. Moreover, we find that while dust can in principle survive embedded in the accelerated clouds, the survival fraction depends critically on the time dust spends in the hot phase and on the effective threshold temperature for destruction. We discuss our results in the context of polluting the circumgalactic medium with dust and metals, as well as understanding observations suggesting rapid acceleration of molecular galactic winds and ram pressure stripped tails of jellyfish galaxies.

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Observation of Acceleration of H i Clouds within the Fermi Bubbles

Cited by 38 publications

References 35 publications

Cool outflows in galaxies and their implications

Cool outflows in galaxies and their implications

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

The Survival of Multiphase Dusty Clouds in Hot Winds

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