J/other/NatAs/4.1072 HaloSat survey of southern Galactic halo (Kaaret+, 2020)
A disc-dominated and clumpy circumgalactic medium of the Milky Way seen
in X-ray emission.
Kaaret P., Koutroumpa D., Kuntz K.D., Jahoda K., Bluem J., Gulick H.,
Hodges-Kluck E., LaRocca D.M., Ringuette R., Zajczyk A.
<Nature Astronomy, 4, 1072-1077 (2020)>
=2020NatAs...4.1072K 2020NatAs...4.1072K (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; X-ray sources ; Interstellar medium
Keywords: Galaxy: halo - ISM: structure - X-rays: diffuse background -
X-rays: ISM
Abstract:
The Milky Way galaxy is surrounded by a circumgalactic medium (CGM)
that may play a key role in galaxy evolution as the source of gas for
star formation and a repository of metals and energy produced by star
formation and nuclear activity. The CGM may also be a repository for
baryons seen in the early universe, but undetected locally. The CGM
has an ionized component at temperatures near 2x106K studied
primarily in the soft X-ray band. Here we report a survey of the
southern Galactic sky with a soft X-ray spectrometer optimized to
study diffuse soft X-ray emission. The X-ray emission is best fit with
a disc-like model based on the radial profile of the surface density
of molecular hydrogen, a tracer of star formation, suggesting that the
X-ray emission is predominantly from hot plasma produced via stellar
feedback. Strong variations in the X-ray emission on angular scales of
∼10 degrees indicate that the CGM is clumpy. Addition of an extended,
and possibly massive, halo component is needed to match the halo
density inferred from other observations.
Description:
The table contains the thermal plasma emission measure and temperature
for the HaloSat southern Galactic halo fields. Also included is the
equivalent sum of OVII and OVIII line emission.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 68 73 Observation details and spectral fit results
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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2- 4 I3 --- ObsID HaloSat observation ID
6- 12 F7.3 deg GLON Galactic longitude
14- 20 F7.3 deg GLAT Galactic latitude
23- 27 I5 s ExpTime Usable exposure time
29- 32 F4.2 --- Cash Cash statistic
34- 38 F5.2 10-3cm-6/pc EM Best-fit halo emission measure
40- 44 F5.2 10-3cm-6/pc e_EM Error on emission measure (90% confidence)
46- 50 F5.3 keV kT Best-fit halo temperature
52- 56 F5.3 keV e_kT Error on halo temperature (90% confidence)
58- 62 F5.2 10-4m-2/s/sr OLU Sum of OVII+OVIII line emission (1)
64- 68 F5.2 10-4m-2/s/sr e_OLU Error on line emission (90% confidence)
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Note (1): Total emission in OVII and OVII is calculated from the best-fit halo
temperature and emission measure and is the sum of following list of lines as
[element, ion, upper level, lower level] energy
[8,7,2,1] 0.561 keV
[8,7,5,1] 0.569 keV
[8,7,7,1] 0.574 keV
[8,8,3,1] 0.653 keV
[8,8,4,1] 0.654 keV
[8,7,13,1] 0.666 keV
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Acknowledgements:
Phillip Kaaret, philip-kaaret(at)uiowa.edu
(End) Patricia Vannier [CDS] 19-Oct-2020