Effect of hot white dwarfs on the interstellar medium. II. Changes in its structure with height above the galactic plane and some consequences of the finite lifetimes and velocities of the white dwarfs

Journal Article · Sun Jul 01 04:00:00 EDT 1973 · Astron. Astrophys., v. 26, no. 2, pp. 197-202

OSTI ID:4378747

Hills, J G

Because the scale height above the galactic plane of the hot white dwarfs (UV stars) is greater than that of the interstellar gas, the interstellar medium above an average height Z =400 pc from the galactic plane is completely ionzed by the UV stars. If half the ionizing radiation from the UV stars above this Z escapes the Galaxy about ten percent of the ionizing photons emitted by the UV stars in the galactic disk escape the Galaxy. A Z-dependent model giving the average properties of the interstellar medium is calculated by assuming that all the ionizing photons emitted by the UV stars at a particular Z are absorbed by the gas at that Z. This model gives, as a function of Z, the fraction of the gas ionized, the fraction of the space occupied by H I clouds, the average density in the interstellar clouds, and the average radius of the intersallar clouds. A preliminary discussion is given of the effect of the finite lifetimes and nonzero velocities of the UV stars on the stucture of the interstellar medium. It is demonstrated that these added factors have little effect on the types of average properties of the interstellar medium discussed in the first part of ihis paper and in the earlier paper (Hills, 1972), but they can account for an additional property of the interstellar medium which is not predictable from a static model, the presence of hot neutral hydrogen between the interstellar clouds. It is estimated that the quantity of hot neutral hydrogen in the intercloud medium is roughly a few time the observed amount of intercloud ionized hydrogen. (auth)

• Research Organization: Univ. of Michigan, Ann Arbor
• NSA Number: NSA-29-013633
• OSTI ID: 4378747
• Journal Information: Astron. Astrophys., v. 26, no. 2, pp. 197-202, Journal Name: Astron. Astrophys., v. 26, no. 2, pp. 197-202; ISSN AAEJA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

*INTERSTELLAR SPACE-- H1 REGIONS
*WHITE DWARF STARS-- VELOCITY
DISTRIBUTION
H2 REGIONS
MILKY WAY
N56200 --Physics (Astrophysics & Cosmology)--Stars
N56500* --Physics (Astrophysics & Cosmology)--Galaxies