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Neutral Hydrogen and the Diffuse Interstellar Medium

Kulkarni, Shrinivas R. and Heiles, Carl (1988) Neutral Hydrogen and the Diffuse Interstellar Medium. In: Galactic and Extragalactic Radio Astronomy. Springer Study Edition. Springer-Verlag , New York, pp. 95-153. ISBN 9780387965758.

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Neutral atomic hydrogen (HI) is an important component of the interstellar medium (ISM). The Galaxy has been estimated to contain about 4.8 x 10^9 M_⊙ of HI (Henderson et al. 1982)*. Estimates for the total amount of H_2 range from 3.5 x 10^9 M_⊙ (Sanders et al. 1984), nearly equal to the HI estimate, to a value that is only 25% of the HI estimate (Bloemen et al. 1986). Galactic HI constitutes about 4.4% of the mass of the visible matter (Bahcall et al. 1983). The mean surface density distribution of HI is roughly constant from about 4 kpc to 20 kpc; however, HI dominates H_2 in mass beyond Galactocentric radius 8 kpc (Blitz et al. 1983). Unlike H_2, HI is not concentrated in a small number of giant clouds. Estimates of the "filling factor", the fraction of the Galactic interstellar space occupied by hydrogen, range from 20% to 90%. These factors establish the preeminence of atomic hydrogen in the dynamics and evolution of the ISM.

Item Type:Book Section
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Kulkarni, Shrinivas R.0000-0001-5390-8563
Additional Information:© 1988 Springer-Verlag. This work was supported in part by National Science Foundation grant no. AST 85-13422, awarded to C. Heiles, and a Robert A. Millikan Fellowship to S.R. Kulkarni.
Funding AgencyGrant Number
NSFAST 85-13422
Caltech Millikan FellowshipUNSPECIFIED
Series Name:Springer Study Edition
Record Number:CaltechAUTHORS:20130307-144919438
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Official Citation:Kulkarni, S. and C. Heiles (1988). Neutral Hydrogen and the Diffuse Interstellar Medium. Galactic and Extragalactic Radio Astronomy. G. Kellerman and K. Kellerman, Springer US: 95-153.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37391
Deposited By: Tony Diaz
Deposited On:04 Apr 2013 23:20
Last Modified:09 Nov 2021 23:28

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