XMM-NEWTON MEASUREMENT OF THE GALACTIC HALO X-RAY EMISSION USING A COMPACT SHADOWING CLOUD

Observations of interstellar clouds that cast shadows in the soft X-ray background can be used to separate the background Galactic halo emission from the local emission due to solar wind charge exchange (SWCX) and/or the Local Bubble (LB). We present an XMM-Newton observation of a shadowing cloud, G...

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Published inThe Astrophysical journal Vol. 799; no. 2; pp. 117 - 10
Main Authors Henley, David B., Shelton, Robin L., Cumbee, Renata S., Stancil, Phillip C.
Format Journal Article
LanguageEnglish
Published United States 01.02.2015
Subjects
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Asymptotic properties
CHARGE EXCHANGE
Clouds
Emission
Emission analysis
EMISSION SPECTROSCOPY
Galactic halos
Halos
INTERSTELLAR SPACE
MILKY WAY
RESOLUTION
SOFT X RADIATION
SOLAR WIND
STAR MODELS
X-rays
XMM (spacecraft)
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Summary:Observations of interstellar clouds that cast shadows in the soft X-ray background can be used to separate the background Galactic halo emission from the local emission due to solar wind charge exchange (SWCX) and/or the Local Bubble (LB). We present an XMM-Newton observation of a shadowing cloud, G225.60-66.40, that is sufficiently compact that the on- and off-shadow spectra can be extracted from a single field of view (unlike previous shadowing observations of the halo with CCD-resolution spectrometers, which consisted of separate on- and off-shadow pointings). We analyzed the spectra using a variety of foreground models: one representing LB emission, and two representing SWCX emission. We found that the resulting halo model parameters (temperature T sub(h) [asymptotically =] 2 x 10 super(6) K, emission measure [varepsilon] sub(h) [asymptotically =] 4 x 10 super(-3) cm super(-6) pc) were not sensitive to the foreground model used. This is likely due to the relative faintness of the foreground emission in this observation. However, the data do favor the existence of a foreground. The halo parameters derived from this observation are in good agreement with those from previous shadowing observations, and from an XMM-Newton survey of the Galactic halo emission. This supports the conclusion that the latter results are not subject to systematic errors, and can confidently be used to test models of the halo emission.
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ISSN:0004-637X
1538-4357
1538-4357
DOI:10.1088/0004-637X/799/2/117