Abstract
Observations of the x-ray diffuse background suggest that a significant fraction of the volume of the Galaxy contains low-density million-degree gas. Large-scale angular structures seen in x-ray all-sky surveys imply the existence of at least three nearb y bubbles of hot gas, Sco-Cen, Orion-Eridanus, and Mono-Gem, in addition to x-ray emitting gas located in the local cavity. The near-isotropy of the high-latitude x-ray background in the 0.5 — 1 keVrange away from identified bubbles is consistent with a large-scale-height few-million-degree x-ray emitting halo or emission from the intragroup medium of the Local Group. Absorption features seen in the x-ray background angular distribution in the 0.1 – 0.28 keV range also place some irregular regions of l ower temperature gas in the halo. In this brief review, I will summarize our knowledge of these hot regions.
I will also touch on our knowledge of the spectrum of the local cavity emission. High-spectral resolution observations reveal that the lowenergy spectrum (E < 0.3 keV) from the local cavity is not consistent with models of the x-ray emission from collisi onal-equilibrium ionization plasmas or from non-equilibrium ionization plasmas. Improved models, particularly those incorporating charge transfer onto solar wind ions, would be helpful in this low energy range. Additional data, particularly an all-sky sur vey at high spectral resolution over the 0.1 – 1 keV range, would also be helpful.
Keywords
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Almy, R. C., McCammon, D., Digel, S. W., Bronfman, L., & May, J. 2000, ApJ 545, 290
Cox, D. P. 1997, in IAU Colloq. 166, The Local Bubble and Beyond, ed. D. Breitschwerdt, M. J. Freyberg, & J. Truemper (Berlin: Springer), p. 121
Cravens, T. E. 2000, ApJ 532, L153
Ebisawa, K., Maeda, Y., Kaneda, H., & Yamauchi, S. 2001, Science 293, 1633
Egger, R. J., & Aschenbach, B. 1995, A&A 294, L25
Heiles, C. 1976, ApJ 208, L137
Iwan, D. 1980, ApJ 239, 316
Koyama, K., Makishima, K., Tanaka, Y., & Tsunemi, H. 1986, PASJ 38, 121
Lallement, R., Welsh, B. Y., Vergeley, J. L., Crifo, F., & Sfeir, D. 2003, A&A 411, 447
McCammon, D., Almy, R., Apodaca, E., et al. 2002, ApJ 576, 188
Nousek, J. A., Fried, P. M., Sanders, W. T., & Kraushaar, W. L. 1982, ApJ 258, 83
Park, S., Finley, J. P., & Dame, T. M. 1998, ApJ, 509, 203
Park, S., Finley, J. P., Snowden, S. L., & Dame, T. M. 1997, ApJ 476, L77
Plucinsky, P. P., Snowden, S. L., Aschenbach, B., et al. 1996, ApJ 463, 224
Reynolds, R. J., & Ogden, P. M., 1979, ApJ 229, 942
Robertson, I. P., & Cravens, T. E. 2003, JGR 108, 8031
Sanders, W. T., Edgar, R. J., Kraushaar, W. L., et al. 2001, ApJ 554, 694
Snowden, S. L. 2001, in The Century of Space Science, ed. J. A. M. Bleeker & J. Geiss (Dordrecht: Kluwer Academic Publishers), 581
Snowden, S. L., Burrows, D. N., Sanders, W. T., et al. 1995, ApJ 439, 399
Snowden, S. L., Egger, R., Finkbeiner, D. P., et al. 1998, ApJ 493, 715
Snowden, S. L., Egger, R., Freyberg, M. J., et al. 1997, ApJ 485, 125
Snowden, S. L., McCammon, D., & Verter, F. 1993, ApJ 409, L21
Sugizaki, M., Mitsuda, K., Kaneda, H., et al. 2001, ApJS 134, 77
Wang, Q. D. 1997, in IAU Colloq. 166, The Local Bubble and Beyond, ed. D. Breitschwerdt, M. J. Freyberg, & J. Truemper (Berlin: Springer), p. 503
Welsh, B. Y., Sfeir, D., Sirk, M., & Lallement, R. 1999, A&A 352, 308
Willingale, R., Hands, A. D. P., Warwick, et al. 2003, MNRAS 343, 995
Worrall, D. M., Marshall, F. E., Boldt, E. A., & Swank, J. H. 1982, ApJ, 255, p. 111
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2004 Kluwer Academic Publishers
About this paper
Cite this paper
Sanders, W.T. (2004). Hot Gas in the Galaxy. In: Alfaro, E.J., Pérez, E., Franco, J. (eds) How does the Galaxy Work?. Astrophysics and Space Science Library, vol 315. Springer, Dordrecht. https://doi.org/10.1007/1-4020-2620-X_31
Download citation
DOI: https://doi.org/10.1007/1-4020-2620-X_31
Publisher Name: Springer, Dordrecht
Print ISBN: 978-1-4020-2619-5
Online ISBN: 978-1-4020-2620-1
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)