A<i>SPITZER</i>-MIPS SEARCH FOR DUST IN COMPACT HIGH-VELOCITY H I CLOUDS

Williams, R.; Mathur, S.; Poindexter, S.; Elvis, M.; Nicastro, F.

doi:10.1088/0004-6256/143/4/82

Cited by 7 publications

(5 citation statements)

References 52 publications

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“…Within the reference models the physical processes of self-gravity and thermal conduction are considered, their simulated velocities are typical for CHVCs, and they have a metallicity of 0.1 Z . These cloud models most resemble actually observed CHVCs (Williams et al 2012).…”

Section: Reference Cloudssupporting

confidence: 79%

Physical effects on compact high-velocity clouds in the circumgalactic medium

Sander,

Hensler

2020

Preprint

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We numerically investigate the evolution of compact high-velocity clouds (CHVCs) passing through a hot, tenuous gas representing the highly-ionized circumgalactic medium (CGM) by applying the adaptive-mesh refinement code Flash.The model clouds start from both hydrostatic and thermal equilibrium and are in pressure balance with the CGM. Here, we present 14 models, divided into two mass categories and two metallicities each and different velocities. We allow for selfgravity and thermal conduction or not. All models experience mass diffusion, radiative cooling, and external heating leading to dissociation and ionization.Our main findings are: 1) self-gravity stabilizes clouds against Rayleigh-Taylor instability which are disrupted within 10 sound-crossing times without; 2) clouds can develop Jeans-instable regions internally even though they are initially below Jeans mass; 3) all clouds lose mass by ram pressure and Kelvin-Helmholtz instability; 4) thermal conduction substantially lowers mass-loss rates, by this, extending the clouds' lifetimes, particularly, more than doubling the lifetime of low-mass clouds; 5) thermal conduction leads to continuous, filamentary stripping, while the removed gas is heated up quickly and mixes efficiently with the ambient CGM; 6) without thermal conduction the removed gas consists of dense, cool, clumpy fragments; 7) thermal conduction might prevent CHVCs from forming stars; 8) clouds decelerated by means of drag from the ambient CGM form head-tail shapes and collapse after they reach velocities characteristic for intermediate-velocity clouds.Conclusively, only sophisticated modelling of CHVCs as non-homogeneous and non-isothermal clouds with thermal conduction and self-gravity explains observed morphologies and naturally leads to the suppression of star formation.

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Section: Reference Cloudssupporting

confidence: 79%

Physical effects on compact high-velocity clouds in the circumgalactic medium

Sander,

Hensler

2020

Preprint

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“…The presence of dust in HVCs is supported by the detection of far-IR emission from Complex C (Miville-Deschênes et al 2005), the detection of molecular hydrogen in the Magellanic Stream (Richter et al 2001b), since H 2 forms on the surface of dust grains, and by UV depletion measurements of the Stream's chemical composition (Fox et al 2013). However, IR emission studies of other HVCs found no evidence for dust (Williams et al 2012;Saul et al 2014), so the average amount of dust in the HVC population is unknown, and could be small. As such, the dust correction factor of 1.8 is uncertain.…”

Section: Dust Depletionmentioning

confidence: 99%

The Mass Inflow and Outflow Rates of the Milky Way

Richter

Ashley

Heckman

et al. 2019

ApJ

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We present new calculations of the mass inflow and outflow rates around the Milky Way (MW), derived from a catalog of ultraviolet metal-line high velocity clouds (HVCs). These calculations are conducted by transforming the HVC velocities into the Galactic Standard of Rest (GSR) reference frame, identifying inflowing (v GSR < 0 km s −1 ) and outflowing (v GSR > 0 km s −1 ) populations, and using observational constraints on the distance, metallicity, dust content, covering fractions, and total silicon column density of each population. After removing HVCs associated with the Magellanic Stream and the Fermi Bubbles, we find inflow and outflow rates in cool (T ∼ 10 4 K) ionized gas of dM in /dt (0.53± 0.23) (d/12 kpc)(Z/0.2Z ) −1 M yr −1 and dM out /dt (0.16 ± 0.07) (d/12 kpc)(Z/0.5Z ) −1 M yr −1 . The apparent excess of inflowing over outflowing gas suggests that the MW is currently in an inflowdominated phase, but the presence of substantial mass flux in both directions supports a Galactic fountain model, in which gas is constantly recycled between the disk and the halo. We also find that the metal flux in both directions (in and out) is indistinguishable. By comparing the outflow rate to the Galactic star formation rate, we present the first estimate of the mass loading factor (η HVC ) of the disk-wide MW wind, finding η HVC (0.10±0.06) (d/12 kpc)(Z/0.5Z ) −1 . Including the contributions from low-and intermediate-velocity clouds and from hot gas would increase these inflow and outflow estimates.

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“…Nidever et al 2010). Commonly, FIR emission is detected towards IVCs (Planck Collaboration XXIV 2011), however, no dust emission could be convincingly associated with HVCs so far (Wakker & Boulanger 1986;Planck Collaboration XXIV 2011;Williams et al 2012;Saul et al 2014;Lenz et al 2016), and in other cases they are only tentatively de-tected (Miville-Deschênes et al 2005;Peek et al 2009). These properties suggest that IVCs may be connected to a Galactic fountain process, while HVCs represent an extragalactic reservoir of gas (e.g.…”

Section: Introductionmentioning

confidence: 99%

All-sky census of Galactic high-latitude molecular intermediate-velocity clouds

Röhser

Kerp

Lenz

et al. 2016

A&A

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Context. The H i halo clouds of the Milky Way, and in particular the intermediate-velocity clouds (IVCs), are thought to be connected to Galactic fountain processes. Observations of fountain clouds are important for understanding the role of matter recycling and accretion onto the Galactic disk and subsequent star formation. Aims. Here, we quantify the amount of molecular gas in the Galactic halo. We focus on the rare class of molecular IVCs (MIVCs) and search for new objects. Methods. The H i-FIR correlation was studied across the entire northern and southern Galactic hemispheres at Galactic latitudes |b| > 20• to determine the amount and distribution of molecular gas in IVCs. We used the most recent large-scale H i and FIR data, the Effelsberg Bonn-H i Survey, the Parkes Galactic All-Sky Survey, and the Planck FIR surveys.Results. We present a catalogue of 239 MIVC candidates on the northern and southern Galactic hemispheres. Among these candidates, all previously known MIVCs are recovered except for one single source. The frequency of candidates differs significantly between the northern and southern Galactic hemispheres and between negative and positive LSR velocities as well.Conclusions. In our approach we analyse the local Galactic environment. Extrapolating our results to the entire Galaxy, the global inflow of atomic and molecular IVC gas onto the Milky Way may account for the major fraction of the gaseous mass that is required to sustain the current Galactic star formation rate.

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ASPITZER-MIPS SEARCH FOR DUST IN COMPACT HIGH-VELOCITY H I CLOUDS

Cited by 7 publications

References 52 publications

Physical effects on compact high-velocity clouds in the circumgalactic medium

Physical effects on compact high-velocity clouds in the circumgalactic medium

The Mass Inflow and Outflow Rates of the Milky Way

All-sky census of Galactic high-latitude molecular intermediate-velocity clouds

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