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Cited by 93Astrophysical Phenomena and ObservationsGalaxies: Formation, Evolution, PhenomenaAstrophysics and Star Formation Studies

Warm‐Hot Gas in and around the Milky Way: Detection and Implications of O vii Absorption toward LMC X‐3

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Wang, Q. D., Yao, Y., Tripp, T. M., Fang, T.‐T., Cui, W., Nicastro, F., Mathur, S., Williams, R. J. +2 more·2005·The Astrophysical Journal
DOI 10.1086/497584
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Abstract

X-ray absorption lines of highly ionized species such as O VII at about zero redshift have been firmly detected in the spectra of several active galactic nuclei. However, the location of the absorbing gas remains a subject of debate. To separate the Galactic and extragalactic contributions to the absorption, we have obtained Chandra LETG-HRC and Far Ultraviolet Spectroscopic Explorer observations of the black hole X-ray binary LMC X-3. We clearly detect the O VII Kα absorption line with an equivalent width of 20(14, 26) mÅ (90% confidence range). The Ne IX Kα absorption line is also detected, albeit marginally. A joint analysis of these lines, together with the nondetection of the O VII Kβ and O VIII Kα lines, gives the temperature, velocity dispersion, and hot oxygen column density as 1.3(0.7,1.8) × 10 6 K, 79(62,132) km s -1 , and 1.9(1.2, 3.2) × 10 16 cm -2 , assuming a collisional ionization equilibrium of the X-ray-absorbing gas and a Galactic interstellar Ne/O number ratio of 0.18. The X-ray data allow us to place a 95% confidence lower limit to the Ne/O ratio as 0.14, but the upper limit is not meaningfully constrained. The O VII line centroid and its relative shift from the Galactic O I Kα absorption line, detected in the same observations, are inconsistent with the systemic velocity of LMC X-3 (+310 km s -1 ). The far-UV spectrum shows O VI absorption at Galactic velocities, but no O VI absorption is detected at the LMC velocity at greater than 3 σ significance. The measured Galactic O VI column density is higher than the value predicted from the O VII-bearing gas, indicating multiphase absorption. Both the nonthermal broadening and the decreasing scale height with the increasing ionization state further suggest an origin of the highly ionized gas in a supernova-driven galactic fountain. In addition, we estimate the warm and hot electron column densities from our detected O II Kα line in the LMC X-3 X-ray spectra and from the dispersion measure of a pulsar in the LMC vicinity. We then infer the O/H ratio of the gas to be ≳ 8 × 10 -5 , consistent with the chemically enriched galactic fountain scenario. We conclude that the Galactic hot interstellar medium should in general substantially contribute to zero-redshift X-ray absorption lines in extragalactic sources.

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  • The Milky Way has a hot circumgalactic medium.

    “Detection of O vi , O vii , and O viii absorption lines along several Galactic and extragalactic sources made it clear that MW has a reserve of hot ( ∼ 10 6 K) gas surrounding it (Nicastro et al. 2003; Sembach et al. 2003; Wang et al. 2005).”

    From The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way (2024) · cites this paper as Wang et al. 2005

    Section 4.3 places the bulk of the highly ionized gas near the Milky Way, but says it is most likely in a thick hot gaseous disk. It allows for a larger halo without establishing one, so the claim that the detected gas is a circumgalactic medium surrounding the Milky Way overstates this source. (LLM, conf=0.86)

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Research works printed but not linked: 1

  1. Wang, Q. D., & Yao, Y. 2005, in AIP Conf. Ser. 774, X-ray Diagnostics for Astrophysical Plasmas, ed.

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Authors
Wang, Q. D., Yao, Y., Tripp, T. M., Fang, T. ‐., Cui, W., Nicastro, F., Mathur, S., Williams, R. J., Song, L., & Croft, R.
Affiliations
  • University of Massachusetts Amherst (US)
  • University of California, Berkeley (US)
  • Purdue University West Lafayette (US)
  • Center for Astrophysics Harvard & Smithsonian (US)
  • The Ohio State University (US)
  • Carnegie Mellon University (US)
ORCID
Venue
The Astrophysical Journal
Publisher
American Astronomical Society
Published
2005-12-10
Volume
635
Issue
1
Pages
386-395
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
DOI
10.1086/497584
OpenAlex
W2014794978
Cited by
93
References
61
Citations by year
2026: 2 · 2025: 2 · 2024: 5 · 2023: 1 · 2022: 1 · 2021: 3 · 2020: 5 · 2019: 1 · 2018: 9 · 2017: 3 · 2016: 9 · 2015: 3 · 2014: 2 · 2013: 3 · 2012: 5
FWCI
5.23
Type
journal article
Language
en
Open access
Locations
  • The Astrophysical Journal (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • Purdue e-Pubs (Purdue University System) (submittedVersion)
  • Scholarworks (University of Massachusetts Amherst) (submittedVersion)
  • CERN Document Server (European Organization for Nuclear Research) (submittedVersion)
  • ScholarWorks@UMassAmherst (University of Massachusetts Amherst) (submittedVersion)
  • arXiv (Cornell University)
  • University of Massachusetts (UMass) Amherst
Funders
  • National Aeronautics and Space Administration (NAS5-32985, NNG04GG73G)
  • Johns Hopkins University
  • Centre National d’Etudes Spatiales
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysics and Star Formation Studies
Keywords
Galactic halo, LMC X-3, O VI absorption, highly ionized plasma, galactic chemical enrichment, Ne/O ratio, oxygen abundance, electron column density, pulsar dispersion measure, X-ray absorption lines, collisional ionization equilibrium, black hole X-ray binaries

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