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Cited by 58Astrophysics and Cosmic PhenomenaAstrophysical Phenomena and ObservationsAstrophysics and Star Formation Studies

The X-ray spectrum of the North Polar Spur

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Willingale, R., Hands, A. D. P., Warwick, R. S., Snowden, S. L., Burrows, D. N.·2003·Monthly Notices of the Royal Astronomical Society
DOI 10.1046/j.1365-8711.2003.06741.x
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Abstract

An analysis is presented of the soft X-ray background spectrum measured by the EPIC-MOS cameras on XMM–Newton in three observations targeted on the North Polar Spur (NPS). Three distinct Galactic plasma components are identified: a cool local hot bubble (LHB) component, Tlo∼ 0.1 keV; a cool Galactic halo component, at a similar temperature; and a hotter component, Thi∼ 0.26 keV, associated with the NPS itself. Using the new data in combination with the ROSAT All-Sky Survey count rates measured in the 0.1–0.4 keV band, we estimate the emission measure of the LHB material to be 0.0040–0.0052 cm−6 pc, which implies an electron density of 0.008–0.011 cm−3 and pressure of ∼22 000 cm−3 K. The halo and NPS components lie behind at least 50 per cent of the line-of-sight cold gas for which the total Galactic column density is in the range (2–8) × 1020 cm−2. Modelling the X-ray emitting superbubble as a sphere at distance 210 pc, radius 140 pc and centre lII= 352°, bII= 15°, the implied electron density in the NPS is ∼0.03 cm−3 with pressure ∼150 000 cm−3 K. The observed spectral line complexes from O vii, O viii, Fe xvii, Ne ix, Ne x and Mg xi provide constraints on the composition of the plasma. The hot component in the NPS is depleted in oxygen, neon and, to some extent, magnesium and iron. Assuming that the effective line of sight across the halo emission is 1 kpc, the electron density in the halo is 0.007–0.011 cm−3 and the pressure is ∼16 500 cm−3 K, conditions very similar to those in the LHB.

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  • X-ray observations toward the NPS imply an absorbing Hydrogen column density of about 3 × 10^20 cm^-2, close to the Galactic values in those directions.

    “Xray observations toward the NPS find that the spectra imply an absorbing Hydrogen column density of ∼ 3 × 10 20 cm -2 (Willingale et al. 2003; Kataoka et al. 2013), close to the Galactic values in those directions.”

    From The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way (2024) · cites this paper as Willingale et al. 2003

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Authors
Willingale, R., Hands, A. D. P., Warwick, R. S., Snowden, S. L., & Burrows, D. N.
Affiliations
  • University of Leicester (GB)
  • Goddard Space Flight Center (US)
  • Pennsylvania State University (US)
ORCID
Venue
Monthly Notices of the Royal Astronomical Society
Publisher
Oxford University Press (OUP)
Published
2003-08-11
Volume
343
Issue
3
Pages
995-1001
ISSN
  • 0035-8711 (ISSN-L)
  • 1365-2966
DOI
10.1046/j.1365-8711.2003.06741.x
OpenAlex
W2086899849
Cited by
58
References
2
Citations by year
2026: 1 · 2025: 1 · 2024: 2 · 2022: 1 · 2020: 3 · 2018: 4 · 2016: 6 · 2015: 6 · 2014: 1 · 2013: 2
FWCI
1.24
Type
journal article
Language
en
Open access
Locations
  • Monthly Notices of the Royal Astronomical Society (publishedVersion)
  • NASA STI Repository (National Aeronautics and Space Administration) (submittedVersion)
  • Leicester Research Archive (University of Leicester) (submittedVersion)
Topics
  • Physical Sciences › Physics and Astronomy › Nuclear and High Energy Physics › Astrophysics and Cosmic Phenomena
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysics and Star Formation Studies
Keywords
North Polar Spur, soft X-ray background, Local Hot Bubble, Galactic halo, superbubbles, X-ray emission measure, electron density, plasma pressure, elemental depletion, ROSAT All-Sky Survey

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