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Optically Thin Thermal Plasma in the Galactic Bulge

from Part 5 - Bulge Phenomenology

Published online by Cambridge University Press:  10 November 2010

By
Y. Maeda ,
G. Garmire ,
K. Koyama  and
M. Sakano
Edited by
C. Marcella Carollo ,
Henry C. Ferguson  and
Rosemary F. G. Wyse
Y. Maeda
Affiliation:
Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A.
G. Garmire
Affiliation:
Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A.
K. Koyama
Affiliation:
Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; CREST, Japan Science and Technology Corporation (JST), 4-1-8 Honmachi, Kawaguchi, Saitama 332-0012, Japan
M. Sakano
Affiliation:
Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
C. Marcella Carollo
Affiliation:
Columbia University, New York
Henry C. Ferguson
Affiliation:
Space Telescope Science Institute, Baltimore
Rosemary F. G. Wyse
Affiliation:
The Johns Hopkins University
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Summary

We present preliminary results of our ASCA observation of the Galactic bulge. We confirm the diffuse (spatially-unresolved) soft X-ray emission in the direction of the bulge. We also detect iron-L and neon-K complex lines in the spectrum. Therefore, the bulge emission undoubtedly originates from an optically thin thermal plasma. The plasma temperature is 0.4 keV. With the results, we present possible implications of the Galactic bulge emission.

Introduction

A Galactic Soft X-ray Diffuse Background (SXDB) below ∼2 keV was discovered by Bowyer, Field & Mack (1968). Four soft X-ray all-sky surveys produced maps of this SXDB (McCammon et al. 1983; Marshall & Clark 1984; Garmire et al. 1992; Snowden et al. 1995, 1997) which show complex features, indicating that the SXDB must be made up of several components. However, Snowden et al. (1997) established that the SXDB maps above 0.5 keV are smooth on the south side of the plane, which can be reproduced with only one component: a hot gas in the bulge with a scale height of ∼1.9 kpc. Thus they named this component as the ‘bulge’ emission. The typical temperature was estimated to be ∼0.3 keV.

The ASCA satellite has the capability to observe the SXDB with a reasonable energy resolution (Tanaka et al. 1994), which allows an improved study of line emission. We present here results of our initial analysis of the ASCA spectrum and discuss the bulge emission.

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Information
The Formation of Galactic Bulges , pp. 175 - 179
Publisher: Cambridge University Press
Print publication year: 2000

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  • Optically Thin Thermal Plasma in the Galactic Bulge
    • By Y. Maeda, Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A., G. Garmire, Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A., K. Koyama, Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; CREST, Japan Science and Technology Corporation (JST), 4-1-8 Honmachi, Kawaguchi, Saitama 332-0012, Japan, M. Sakano, Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
  • Edited by C. Marcella Carollo, Columbia University, New York, Henry C. Ferguson, Space Telescope Science Institute, Baltimore, Rosemary F. G. Wyse, The Johns Hopkins University
  • Book: The Formation of Galactic Bulges
  • Online publication: 10 November 2010
  • Chapter DOI: https://doi.org/10.1017/CBO9780511564611.029
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  • Optically Thin Thermal Plasma in the Galactic Bulge
    • By Y. Maeda, Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A., G. Garmire, Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A., K. Koyama, Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; CREST, Japan Science and Technology Corporation (JST), 4-1-8 Honmachi, Kawaguchi, Saitama 332-0012, Japan, M. Sakano, Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
  • Edited by C. Marcella Carollo, Columbia University, New York, Henry C. Ferguson, Space Telescope Science Institute, Baltimore, Rosemary F. G. Wyse, The Johns Hopkins University
  • Book: The Formation of Galactic Bulges
  • Online publication: 10 November 2010
  • Chapter DOI: https://doi.org/10.1017/CBO9780511564611.029
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Optically Thin Thermal Plasma in the Galactic Bulge
    • By Y. Maeda, Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A., G. Garmire, Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A., K. Koyama, Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; CREST, Japan Science and Technology Corporation (JST), 4-1-8 Honmachi, Kawaguchi, Saitama 332-0012, Japan, M. Sakano, Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
  • Edited by C. Marcella Carollo, Columbia University, New York, Henry C. Ferguson, Space Telescope Science Institute, Baltimore, Rosemary F. G. Wyse, The Johns Hopkins University
  • Book: The Formation of Galactic Bulges
  • Online publication: 10 November 2010
  • Chapter DOI: https://doi.org/10.1017/CBO9780511564611.029
Available formats
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