How was the Mushroom‐shaped GW 123.4−1.5 Formed in the Galactic Disk?

Baek, Chang Hyun; Kudoh, Takahiro; Tomisaka, Kohji

doi:10.1086/589556

Cited by 5 publications

(10 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…HVC accretion events and non-thermal phenomena HVCs striking the disk without much prior deceleration will give rise to forward shocks in the disk gas and/or reverse shocks within the HVC that can be strong depending on the conditions (e.g. Tenorio-Tagle et al 1986Baek et al 2008). Although the thermal emission from the shocked gas expected in the UV to soft X-ray band is likely difficult to observe, an interesting question is whether such shocks can generate high-energy protons and electrons via diffusive shock acceleration (DSA; e.g.…”

Section: High Velocity Clouds and Accretionmentioning

confidence: 99%

“…A more detailed description warrants hydrodynamical simulations (e.g. Tenorio-Tagle et al 1986Kudoh & Basu 2004;Baek et al 2008), which are beyond the scope of this paper.…”

Section: Shock Velocity and Lifetimementioning

confidence: 99%

“…First, as there must be a distribution in v acc , only a part ofṀ acc,HVC corresponds to direct accretion onto the disk with v acc ∼ 300 km s −1 . Second, some HVCs may penetrate the disk while dissipating only a fraction of their kinetic energy (Tenorio-Tagle et al 1986Baek et al 2008). A realistic value of f acc is difficult to estimate, but f acc ≪ 1 is possible if much of the accretion turns out to proceed quietly with low v acc (e.g.…”

Section: Energetics and Numbermentioning

confidence: 99%

“…In comparison, our interpretation of the latter at a younger age of t ∼ 10 6 yr implies that it is only nearing the transition from adiabatic to radiative ( §2.2, §3.4). Thus the conditions of the parent HVC may be rather closer to its pre-impact state, although this can also depend on the collision parameters and geometry (Baek et al 2008).…”

Section: Prospects For Further Observationsmentioning

confidence: 99%

See 3 more Smart Citations

Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk

Inoue

Uchiyama

Arakawa

et al. 2017

ApJ

View full text Add to dashboard Cite

On both observational and theoretical grounds, the disk of our Galaxy should be accreting cool gas with temperature 10 5 K via the halo at a rate ∼ 1 M ⊙ yr −1 . At least some of this accretion is mediated by high velocity clouds (HVCs), observed to be traveling in the halo with velocities of a few 100 km s −1 and occasionally impacting the disk at such velocities, especially in the outer regions of the Galaxy. We address the possibility of particle acceleration in shocks triggered by such HVC accretion events, and the detectability of consequent non-thermal emission in the radio to gamma-ray bands and high-energy neutrinos. For plausible shock velocities ∼ 300 km s −1 and magnetic field strengths ∼ 0.3 − 10 µG, electrons and protons may be accelerated up to ∼ 1 − 10 TeV and ∼ 30 − 10 3 TeV, respectively, in sufficiently strong adiabatic shocks during their lifetime of ∼ 10 6 yr. The resultant pion decay and inverse Compton gamma-rays may be the origin of some unidentified Galactic GeV-TeV sources, particularly the "dark" source HESS J1503-582 that is spatially coincident with anomalous HI structure known as "forbidden-velocity wings". Correlation of their locations with star-forming regions may be weak, absent, or even opposite. Non-thermal radio and X-ray emission from primary and/or secondary electrons may be detectable with deeper observations. The contribution of HVC accretion to Galactic cosmic rays is subdominant, but could be non-negligible in the outer Galaxy. As the thermal emission induced by HVC accretion is likely difficult to detect, observations of such phenomena may offer a unique perspective on probing gas accretion onto the Milky Way and other galaxies.

show abstract

Section: High Velocity Clouds and Accretionmentioning

confidence: 99%

“…A more detailed description warrants hydrodynamical simulations (e.g. Tenorio-Tagle et al 1986Kudoh & Basu 2004;Baek et al 2008), which are beyond the scope of this paper.…”

Section: Shock Velocity and Lifetimementioning

confidence: 99%

Section: Energetics and Numbermentioning

confidence: 99%

Section: Prospects For Further Observationsmentioning

confidence: 99%

See 2 more Smart Citations

Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk

Inoue

Uchiyama

Arakawa

et al. 2017

ApJ

View full text Add to dashboard Cite

show abstract

“…Galactic worms were first identified as irregular, vertical columns of atomic gas stretching from the galactic plane; now, similar structures are found in radio continuum and infrared maps, see e.g. Koo, Heiles & Reach (1992), English et al (2000) and Baek, Kudoh & Tomisaka (2008). The models that explain the SB as being due to the combined explosions of supernova (SN) in a cluster of massive stars will now be briefly reviewed.…”

Section: Introductionmentioning

confidence: 76%

Evolution of superbubbles in a self-gravitating disc

Zaninetti¹

2012

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The expansion of a superbubble is investigated both analytically and numerically. Our model implements the thin‐layer approximation in a vertical profile of density as given by an isothermal self‐gravitating disc. A precise comparison with the results of numerical hydrodynamics is given. Analogies are drawn with the Kompaneets equation that includes the quadratic hyperbolic‐secant law in the list of the plane‐parallel stratified media. An astrophysical application is made to the superbubble connected with the two worms 46.4+5.5 and 39.7+5.7. The effects of the rotation of the Galaxy on the simulated radius and on the velocity are introduced. The worms with their strong limb brightening visible on astronomical maps are explained in the framework of image theory.

show abstract

Formation of Galactic Center Magnetic Loops

Machida

Matsumoto

Nozawa

et al. 2009

Publications of the Astronomical Society of Japan

Self Cite

View full text Add to dashboard Cite

A survey for the molecular clouds in the Galaxy with NANTEN mm telescope has discovered molecular loops in the Galactic center region. The loops show monotonic gradients of the line of sight velocity along the loops and the large velocity dispersions towards their foot points. It is suggested that these loops are explained in terms of the buoyant rise of magnetic loops due to the Parker instability. We have carried out global three-dimensional magneto-hydrodynamic simulations of the gas disk in the Galactic center. The gravitational potential is approximated by the axisymmetric potential proposed by Miyamoto & Nagai (1975). At the initial state, we assume a warm (∼ 10 4 K) gas torus threaded by azimuthal magnetic fields. Self-gravity and radiative cooling of the gas are ignored. We found that buoyantly rising magnetic loops are formed above the differentially rotating, magnetically turbulent disk. By analyzing the results of global MHD simulations, we have identified individual loops, about 180 in the upper half of the disk, and studied their statistical properties such as their length, width, height, and velocity distributions along the loops. Typical length and height of a loop are 1kpc and 200pc, respectively. The line of sight velocity changes linearly along a loop and shows large dispersions around the foot-points. 1Numerical results indicate that loops emerge preferentially from the region where magnetic pressure is large. We argue that these properties are consistent with those of the molecular loops discovered by NANTEN.

show abstract

How was the Mushroom‐shaped GW 123.4−1.5 Formed in the Galactic Disk?

Cited by 5 publications

References 18 publications

Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk

Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk

Evolution of superbubbles in a self-gravitating disc

Formation of Galactic Center Magnetic Loops

Contact Info

Product

Resources

About