UNRAVELING THE ORIGIN OF OVERIONIZED PLASMA IN THE GALACTIC SUPERNOVA REMNANT W49B
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Lopez-2013-UNRAVELING THE ORIGI.pdf
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Author(s)
Lopez, Laura A.
Pearson, Sarah
Ramirez-Ruiz, Enrico
Castro, Daniel
Yamaguchi, Hiroya
Slane, Patrick O.
Smith, Randall K.
Date Issued
November 2013
Journal
Astrophysical Journal
Publisher
Institute of Physics/American Astronomical Society
Citation
Lopez, Laura A., Sarah Pearson, Enrico Ramirez-Ruiz, Daniel Castro, Hiroya Yamaguchi, Patrick O. Slane, and Randall K. Smith. “UNRAVELING THE ORIGIN OF OVERIONIZED PLASMA IN THE GALACTIC SUPERNOVA REMNANT W49B.” The Astrophysical Journal 777, no. 2 (October 23, 2013): 145. © 2013 American Astronomical Society.
Version
Final published version
Abstract
Recent observations have shown several supernova remnants (SNRs) have overionized plasmas, where ions are stripped of more electrons than they would be if in equilibrium with the electron temperature. Rapid electron cooling is necessary to produce this situation, yet the physical origin of that cooling remains uncertain. To assess the cooling scenario responsible for overionization, in this paper we identify and map the overionized plasma in the Galactic SNR W49B based on a 220 ks Chandra Advanced CCD Imaging Spectrometer observation. We performed a spatially resolved spectroscopic analysis, measuring the electron temperature by modeling the continuum and comparing it to the temperature given by the flux ratio of the He-like and H-like lines of sulfur and argon. Using these results, we find that W49B is overionized in the west, with a gradient of overionization increasing from east to west. As the ejecta expansion is impeded by molecular material in the east but not in the west, our overionization maps suggest the dominant cooling mechanism is adiabatic expansion of the hot plasma.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.1088/0004-637x/777/2/145
