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Title: 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 ∼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{sub −0.44}{sup +0.47})×10{sup 6} K and a 0.4-2.0 keV luminosity of 7.9 × 10{sup 33} erg s{sup –1}. However, this model underpredicts the on-enhancement emission around 1 keV, which may indicate the additional presence of hotter plasma (T ≳ 10{sup 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 warmmore » 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.« less

Authors:
;  [1];  [2]
  1. Department of Physics and Astronomy, University of Georgia, Athens, GA 30602 (United States)
  2. School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan 689-798 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22365388
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 791; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ATOMS; CHARGE-EXCHANGE REACTIONS; COMPRESSION; EMISSION; EQUILIBRIUM PLASMA; GALAXIES; KEV RANGE; LUMINOSITY; MAGNETIC FIELDS; MAGNETIC RECONNECTION; MAGNETOHYDRODYNAMICS; MIXING; RECOMBINATION; SIMULATION; SOFT X RADIATION; STREAMS; VELOCITY

Citation Formats

Henley, David B., Shelton, Robin L., and Kwak, Kyujin, E-mail: dbh@physast.uga.edu, E-mail: rls@physast.uga.edu, E-mail: kkwak@unist.ac.kr. The origin of the X-ray emission from the high-velocity cloud MS30.7–81.4–118. United States: N. p., 2014. Web. doi:10.1088/0004-637X/791/1/41.
Henley, David B., Shelton, Robin L., & Kwak, Kyujin, E-mail: dbh@physast.uga.edu, E-mail: rls@physast.uga.edu, E-mail: kkwak@unist.ac.kr. The origin of the X-ray emission from the high-velocity cloud MS30.7–81.4–118. United States. doi:10.1088/0004-637X/791/1/41.
Henley, David B., Shelton, Robin L., and Kwak, Kyujin, E-mail: dbh@physast.uga.edu, E-mail: rls@physast.uga.edu, E-mail: kkwak@unist.ac.kr. Sun . "The origin of the X-ray emission from the high-velocity cloud MS30.7–81.4–118". United States. doi:10.1088/0004-637X/791/1/41.
@article{osti_22365388,
title = {The origin of the X-ray emission from the high-velocity cloud MS30.7–81.4–118},
author = {Henley, David B. and Shelton, Robin L. and Kwak, Kyujin, E-mail: dbh@physast.uga.edu, E-mail: rls@physast.uga.edu, E-mail: kkwak@unist.ac.kr},
abstractNote = {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{sub −0.44}{sup +0.47})×10{sup 6} K and a 0.4-2.0 keV luminosity of 7.9 × 10{sup 33} erg s{sup –1}. However, this model underpredicts the on-enhancement emission around 1 keV, which may indicate the additional presence of hotter plasma (T ≳ 10{sup 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.},
doi = {10.1088/0004-637X/791/1/41},
journal = {Astrophysical Journal},
number = 1,
volume = 791,
place = {United States},
year = {Sun Aug 10 00:00:00 EDT 2014},
month = {Sun Aug 10 00:00:00 EDT 2014}
}
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