Modeling the X-Rays Resulting From High-Velocity Clouds

Shelton, R. L.; Kwak, Kyujin; Henley, David

doi:10.1088/0004-637x/751/2/120

Cited by 11 publications

(19 citation statements)

References 36 publications

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“…Similar results were also found in a set of simulations carried out using the FLASH code (Kwak et al 2011;Shelton et al 2012;Gritton et al 2014Gritton et al , 2017, where they studied individual cold clouds interacting with a hot atmosphere. Outflows in these simulations were generally implemented using the constant density and velocity wind-tunnel model.…”

Section: Comparison To Previous Worksupporting

confidence: 78%

Simulating Gas Inflow at the Disk–Halo Interface

Melso

Bryan²,

Li³

2019

ApJ

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The interaction between inflowing gas clouds and galactic outflows at the interface where the galactic disk transitions into the circumgalactic medium is an important process in galaxy fueling, yet remains poorly understood. Using a series of tall-box hydrodynamic Enzo simulations, we have studied the interaction between smooth gas inflow and supernovae-driven outflow at the disk-halo interface with pc-scale resolution. A realistic wind of outflowing material is generated by supernovae explosions in the disk, while inflowing gas is injected at the top boundary of the simulation box with an injection velocity ranging from 10 − 100 km s −1 . We find that cooling and hydrodynamic instabilities drive the injected gas to fragment into cold (∼ 10 3 K) cloud clumps with typical densities of ∼ 1 cm −3 . These clumps initially accelerate before interacting and partially mixing with the outflow and decelerating to velocities in the 50-100 km s −1 range. When the gas clumps hit the disk, 10% − 50% of the injected material is able to accrete (depending on the injection velocity). Clumps originating from gas injected with a higher initial velocity approach the disk with greater ram pressure, allowing them to penetrate through the disk in low density regions. We use (equilibrium) Cloudy photoionization models to generate absorption and emission signatures of gas accretion, finding that our mock HI and Hα observables are prominent and generally consistent with measurements in the Milky Way. We do not predict enhanced emission/absorption for higher ionization states such as OVI.

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Section: Comparison To Previous Worksupporting

confidence: 78%

Simulating Gas Inflow at the Disk–Halo Interface

Melso

Bryan²,

Li³

2019

ApJ

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“…Note that the speed in the above expression is the speed at which material crosses the shock, which may be somewhat faster than the speed of the cloud, as the shock tends to move away from the cloud as the cloud and shock evolve, at least in the early stages of the cloud's evolution. Hydrodynamical simulations imply that the shock speed exceeds the cloud speed by 10% for strong shocks in cool and warm ambient media induced by initially round clouds (Shelton et al 2012). Note also that, in practice, the average post-shock temperature behind an HVC's bow shock would be lower than that expected from Equation (3) for a number of reasons, especially if the cloud is traveling through relatively dense cool or warm gas: (1) gas toward the side of the cloud will hit the bow shock obliquely, reducing the postshock temperature, (2) the cloud will decelerate as it passes through the dense gas, weakening the shock, and (3) radiative cooling will be important in the dense shocked gas.…”

Section: Strong Shocksmentioning

confidence: 99%

“…We further investigated shock heating using the Case B hydrodynamical models of Shelton et al (2012). In these models, the initially spherical cloud hits warm gas (possibly representing material shed from a preceding cloud; T = 10 4 K, n H = 6.45 × 10 −3 cm −3 ), after passing through hot halo gas (T = 10 6 K, n H = 6.45 × 10 −5 cm −3 ).…”

Section: Predictions From Shelton Et Al (2012) Hvc Modelsmentioning

confidence: 99%

“…For each epoch of each model, we calculated the spectrum averaged over a radius of 50 pc from the cloud center (for an observer looking directly along the cloud's velocity vector). The spectra were calculated assuming CIE (see Shelton et al 2012 for more details of the spectral calculations). We did not subtract off the contribution from the ambient medium in the model, to avoid potentially having to deal with negative model count rates.…”

Section: Predictions From Shelton Et Al (2012) Hvc Modelsmentioning

confidence: 99%

“…In contrast, MS30.7's speed is unlikely to exceed ∼400 km s −1 (Section 4.1). In the context of MS30.7, the denser warm ambient medium in the Shelton et al (2012) models could represent material shed from a preceding cloud. In this case, the speed of MS30.7 relative to this material is likely to be even less than the orbital speed of the Mag- ellanic Stream.…”

Section: Summary Of Shock Heatingmentioning

confidence: 99%

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The Origin of the X-Ray Emission From the High-Velocity Cloud MS30.7–81.4–118

Henley¹,

Shelton²,

Kwak

2014

ApJ

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A soft X-ray enhancement has recently been reported toward the high-velocity cloud MS30.7−81.4−118 (MS30.7), a constituent of the Magellanic Stream. In order to investigate the origin of this enhancement, we have analyzed two overlapping XMM-Newton observations of this cloud. We find that the X-ray enhancement is ∼6 ′ or ∼100 pc across, and is concentrated to the north and west of the densest part of the cloud. We modeled the X-ray enhancement with a variety of spectral models. A single-temperature equilibrium plasma model yields a temperature of (3.69 +0.47 −0.44 ) × 10 6 K and a 0.4-2.0 keV luminosity of 7.9 × 10 33 erg s −1 . However, this model underpredicts the on-enhancement emission around 1 keV, which may indicate the additional presence of hotter plasma (T 10 7 K), or that recombination emission is important. We examined several different physical models for the origin of the X-ray enhancement. We find that turbulent mixing of cold cloud material with hot ambient material, compression or shock heating of a hot ambient medium, and charge exchange reactions between cloud atoms and ions in a hot ambient medium all lead to emission that is too faint. In addition, shock heating in a cool or warm medium leads to emission that is too soft (for reasonable cloud speeds). We find that magnetic reconnection could plausibly power the observed X-ray emission, but resistive magnetohydrodynamical simulations are needed to test this hypothesis. If magnetic reconnection is responsible for the X-ray enhancement, the observed spectral properties could potentially constrain the magnetic field in the vicinity of the Magellanic Stream.

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A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

Boselli

Fossati

Ferrarese

et al. 2018

A&A

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The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band (NB) Hα+[NII] imaging survey carried out with MegaCam at the Canada–France–Hawaii Telescope. The survey covers the whole Virgo cluster region from its core to one virial radius (104 deg2). The sensitivity of the survey is of f(Hα) ~ 4 × 10−17 erg s−1 cm−2 (5σ detection limit) for point sources and Σ(Hα) ~ 2 × 10−18 erg s−1 cm−2 arcsec−2 (1σ detection limit at 3 arcsec resolution) for extended sources, making VESTIGE the deepest and largest blind NB survey of a nearby cluster. This paper presents the survey in all its technical aspects, including the survey design, the observing strategy, the achieved sensitivity in both the NB Hα+[NII] and in the broad-band r filter used for the stellar continuum subtraction, the data reduction, calibration, and products, as well as its status after the first observing semester. We briefly describe the Hα properties of galaxies located in a 4 × 1 deg2 strip in the core of the cluster north of M87, where several extended tails of ionised gas are detected. This paper also lists the main scientific motivations for VESTIGE, which include the study of the effects of the environment on galaxy evolution, the fate of the stripped gas in cluster objects, the star formation process in nearby galaxies of different type and stellar mass, the determination of the Hα luminosity function and of the Hα scaling relations down to ~106 M⊙ stellar mass objects, and the reconstruction of the dynamical structure of the Virgo cluster. This unique set of data will also be used to study the HII luminosity function in hundreds of galaxies, the diffuse Hα+[NII] emission of the Milky Way at high Galactic latitude, and the properties of emission line galaxies at high redshift.

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Modeling the X-Rays Resulting From High-Velocity Clouds

Cited by 11 publications

References 36 publications

Simulating Gas Inflow at the Disk–Halo Interface

Simulating Gas Inflow at the Disk–Halo Interface

The Origin of the X-Ray Emission From the High-Velocity Cloud MS30.7–81.4–118

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

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