The Origin of the X-ray Emission from the High-velocity Cloud MS30.7-81.4-118

Abstract

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 $\sim$6' or $\sim$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 $(3.69_{-0.44}^{+0.47})\times 10^6$ K and a 0.4-2.0 keV luminosity of $7.9\times 10^{33}$ erg s${}^{-1}$. However, this model underpredicts the on-enhancement emission around 1 keV, which may indicate the additional presence of hotter plasma ($T\gtrsim 10^7$ 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.

arXiv comment17 pages, 6 figures. Accepted for publication in the Astrophysical Journal

References in corpus (43)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The chemical composition of the Sun
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of Hydrogen-like and Helium-like Ions
• Where are the Baryons?
• Ionization balance for optically thin plasmas: rate coefficients for all atoms and ions of the elements H to Ni
• Updated Atomic Data and Calculations for X-ray Spectroscopy
• Highly-Ionized High-Velocity Gas in the Vicinity of the Galaxy
• Atomic data for astrophysics. I. Radiative recombination rates for H-like, He-like, Li-like and Na-like ions over a broad range of temperature
• Absolute measurement of the unresolved cosmic X-ray background in the 0.5-8 keV band with Chandra
• The resolved fraction of the Cosmic X-ray Background
• The GEMS project: X-ray analysis and statistical properties of the group sample
• N-body Simulations of the Small Magellanic Cloud and the Magellanic Stream
• The Proper Motion of the Large Magellanic Cloud using HST
• The Vertical Structure of Warm Ionised Gas in the Milky Way
• The Magellanic Stream, High-Velocity Clouds and the Sculptor Group
• Is the SMC Bound to the LMC? The HST Proper Motion of the SMC
• The Origin of the Magellanic Stream and Its Leading Arm
• The Parkes HI Survey of the Magellanic System
• Multi-phase High-Velocity Clouds toward HE 0226-4110 and PG 0953+414
• Energy Spectra of the Soft X-ray Diffuse Emission in Fourteen Fields Observed with Suzaku
• Highly Ionized Gas Surrounding High Velocity Cloud Complex C
• The Source of Ionization along the Magellanic Stream
• An XMM-Newton Survey of the Soft X-ray Background. III. The Galactic Halo X-ray Emission
• Charge-Transfer induced EUV and Soft X-ray emissions in the Heliosphere
• Discovery of 14 radio pulsars in a survey of the Magellanic Clouds
• A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds
• Suzaku Observations of the Local and Distant Hot ISM
• OVII and OVIII line emission in the diffuse soft X-ray background: heliospheric and galactic contributions
• The Collisions of HVCs with a Magnetized Gaseous Galactic Disk
• The COS/UVES Absorption Survey of the Magellanic Stream: I. One-Tenth Solar Abundances along the Body of the Stream
• Metallicity and Ionization in High Velocity Cloud Complex C
• Simulations of High-Velocity Clouds. I. Hydrodynamics and High-Velocity High Ions
• A Very Sensitive 21cm Survey for Galactic High-Velocity HI
• Xmm-Newton Observations of the Diffuse X-ray Background
• Comparing Suzaku and XMM-Newton Observations of the Soft X-ray Background: Evidence for Solar Wind Charge Exchange Emission
• Measurement of a Magnetic Field in a Leading Arm High Velocity Cloud
• Properties of the Diffuse X-ray Background toward MBM20 with Suzaku
• Simulations of Supernova Remnants in Diffuse Media. II. Three Remnants and Their X-Ray Emission
• Probing the anisotropy of the Milky Way gaseous halo: Sight-lines toward Mrk 421 and PKS2155-304
• The Evolution of Gas Clouds Falling in the Magnetized Galactic Halo: High Velocity Clouds (HVCs) Originated in the Galactic Fountain
• X-Ray Searches for Emission from the WHIM in the Galactic Halo and the Intergalactic Medium
• Modeling the X-rays Resulting from High Velocity Clouds

Cited by in corpus (6)

• Project AMIGA: The Circumgalactic Medium of Andromeda
• XMM-Newton and Suzaku X-ray Shadowing Measurements of the Solar Wind Charge Exchange, Local Bubble, and Galactic Halo Emission
• The Effect of Mixing on the Observed Metallicity of the Smith Cloud
• XMM-Newton Measurement of the Galactic Halo X-ray Emission using a Compact Shadowing Cloud
• Hydrodynamics of Clustered Clouds: Drafting, Survival, Condensation, and Ablation
• Gamma rays from reaccelerated cosmic rays in high velocity clouds colliding with the Galactic disk