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Ionized Disk/Halo Gas: Insight from Optical Emission Lines and Pulsar Dispersion Measures

Published online by Cambridge University Press:  03 August 2017

R. J. Reynolds
R. J. Reynolds*
Affiliation:
University of Wisconsin-Madison, Department of Physics 1150 University Avenue, Madison, WI 53706, USA

Abstract

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Warm (≈ 104 K), diffuse H+ is a significant component of the interstellar medium within the Galactic disk and lower halo. This gas accounts for about one quarter of the interstellar atomic hydrogen, consumes a large fraction of the interstellar power budget, and appears to be the dominant state of interstellar matter 1 kpc above the midplane. The origin of this ionized gas is not yet established; however, of the known sources of ionization only 0 stars and perhaps supernovae produce enough power to balance the “cooling” rate of the gas. If 0 stars are the source of the ionization, then the interstellar HI, including the extended “Lockman layer”, must have a morphology that allows about 14% of the Lyman continuum photons emitted by the stars to travel hundreds of parsecs within the Galactic disk and up into the lower halo.

Type
I. The Disk-Halo Interface in Our Galaxy
Information
Symposium - International Astronomical Union , Volume 144: The Interstellar Disk-Halo Connection in Galaxies , 1991 , pp. 67 - 76
Copyright
Copyright © Kluwer 1991 

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