J/A+A/698/A313 Galactic centre X-ray reflection map (Anastasopoulou+, 2025)
Disentangling the Galactic centre X-ray reflection signal using XMM-Newton data.
Anastasopoulou K., Khabibullin I., Churazov E., Ponti G., Sormani M.C.,
Sunyaev R.A., Maitra C., Piscitelli S.
<Astron. Astrophys. 698, A313 (2025)>
=2025A&A...698A.313A 2025A&A...698A.313A (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Galactic center ; X-ray sources
Keywords: ISM: clouds - Galaxy: bulge - Galaxy: centre -
Galaxy: disc - X-rays: general - X-rays: ISM
Abstract:
We investigate the X-ray emission from the Galactic Centre (GC)
region, focusing on the 6.4keV fluorescent line of neutral or weakly
ionised iron, which is commonly attributed to X-ray reflection from
dense molecular clouds. Our goal is to separate the reflection signal
from other physical X-ray components. We aim to produce a clean map of
the 6.4keV emission, thus providing a better understanding of the
X-ray reflection processes in the GC.
We utilised a deep mosaic of all available XMM-Newton observations,
encompassing the central 40 square degrees of the Galaxy. This dataset
integrates information from 503 individual observations, resulting in
a total clean exposure time of 7.5Ms. The mosaics of two narrow bands
centred at 6.7keV and 6.4keV, and a broader continuum band at lower
energies (5-6.1keV), provided valuable spatial and spectral
information on the X-ray emission. These combined with the stellar
mass distribution of our Galaxy enabled us to decompose the observed
signal into physically meaningful components.
Our analysis shows that the cleaned 6.4keV band map, free from the
contribution of bright and unresolved point sources, is predominantly
shaped by X-ray reflection from dense molecular clouds. The spatial
distribution of this emission, which strongly correlates with the
molecular gas distribution in the Central Molecular Zone (CMZ),
supports the interpretation that this map provides the best estimate
of the X-ray reflection signal averaged over the last two decades. The
cleaned reflection map produced could serve as a tool for future
studies to quantify upper limits on the reflection contribution from
low-energy cosmic rays in unilluminated regions. Moreover, we estimate
that, on average within the CMZ, approximately 65% of the ridge
emission contributes to the observed emission in the 6.4keV band, a
factor that should be incorporated into upcoming investigations of the
GC such as polarisation studies of the reflected X-ray continuum from
molecular clouds and statistical assessments of the reflection surface
brightness.
Description:
Map of the Galactic Centre and inner Galactic plane of the cleaned 6.4
keV emission representing the reflection. The unit of the presented
map is in counts per second per pixel. The pixel size is 8x8
arcseconds.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 162 1 Information of fits map
fits/* . 1 fits map
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 35 I6 Kibyte size Size of FITS file
37- 51 A15 --- FileName Name of FITS file, in subdirectory fits
53-162 A110 --- Title Title of the FITS file
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Acknowledgements:
Konstantina Anastasopoulou, konstantina.anastasopoulou(at)inaf.it
(End) Patricia Vannier [CDS] 11-May-2025