Abstract
We propose a model explaining the presence of vast regions of partially ionized gas in the interstellar medium. The circumstellar envelope of a hot star absorbs soft ionizing radiation, but transmits an appreciable fraction of the hard photons, which are absorbed much more weakly than photons with energies close to the ionization limit. For this reason, the radiation attenuated by the envelope becomes harder, and can penetrate to larger distances. For stars hotter than 50 000 K, the transition zone between the ionized and neutral gas can extend to tens or hundreds of parsecs. Thus, a region of partially ionized hydrogen, with a small gradient of the degree of ionization without a well-defined inner HII zone, can form in the interstellar medium.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
S. A. Kaplan and S. B. Pikel’ner, Physics of the Interstellar Medium (Nauka, Moscow, 1979) [in Russian].
S. B. Pikel’ner, Astron. Zh. 44, 915 (1967) [Sov. Astron. 11, 737 (1967)].
S. A. Kaplan and S. B. Pikel’ner, The Interstellar Medium (Fizmatgiz, Moscow, 1963) [in Russian].
V. V. Sobolev, Course of Theoretical Astrophysics (Nauka, Moscow, 1975) [in Russian].
V. V. Golovatyi, A. A. Sapar, T. Kh. Feklistova, and A. F. Kholtygin, Atomic Data for Spectroscopy of Low-Density Astrophysical Plasma (Tallinn, 1991).
R. J. Reynolds and F. Scherb, Astrophys. J. 185, 869 (1973).
C. Leitherer et al., Astrophys. J. Lett. 454, L19 (1995).
J. B. Dove and J. M. Shull, Astrophys. J. 423, 196 (1994).
W. W. Miller III and D. P. Cox, Astrophys. J. 417, 579 (1993).
B. J. Weiner and T. B. Williams, Astron. J. 111, 1156 (1996).
G. J. Madsen, Extra-Planar Gas, Ed. by R. Braun (Astron. Soc. Pac., San Francisco, 2005); Astron. Soc. Pac. Conf. Ser. 331, 33 (2005); astroph/0409476 (2004).
L. M. Haffner, Astrophys. J. 523, 223 (1999).
A. Songaila, Astrophys. J. 248, 945 (1981).
W. D. Vacca et al., Astrophys. J. 460, 914 (1996).
E. J. de Geus et al., Astrophys. J. Lett. 413, L97 (1993).
R. F. G. Wyse et al., Publ. Astron. Soc. Aust. 15, 118 (1998).
S. M. Kent et al., Astrophys. J. 378, 131 (1991).
B. Moore and M. Davis, Mon. Not. R. Astron. Soc. 270, 209 (1994).
C. L. Bennett et al., Astrophys. J. 436, 423 (1994).
Author information
Authors and Affiliations
Additional information
Original Russian Text © K.V. Bychkov, M.A. Zaitsev, 2006, published in Astronomicheskiĭ Zhurnal, 2006, Vol. 83, No. 6, pp. 509–515.
Rights and permissions
About this article
Cite this article
Bychkov, K.V., Zaitsev, M.A. Circumstellar envelopes of hot stars: Formation of extended regions of weakly ionized gas. Astron. Rep. 50, 451–457 (2006). https://doi.org/10.1134/S1063772906060047
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1134/S1063772906060047