Rate of production of ionizing radiation by hot white dwarfs and upper main sequence stars in galaxies

Journal Article · Mon Oct 01 04:00:00 EDT 1973 · Astron. Astrophys., v. 28, no. 1, pp. 63-70

OSTI ID:4378621

Hills, J G

Energy conservation dictates that hot white dwarfs (UV stars) produce about one prcent of the stellar luminosity of most galaxies. Since this emission is largely in photons capable of ionlzing hydrogen, there is a direct proportionality between the number of ionizing photons emitted by the UV stars in a galaxy. If the rate of production of the upper main-sequence O and B stars in a galaxy is proportional to the amount of gas being returned to the interstellar medium by evolving stars, there is also a direct proportionality between the number of ionlzing photons being emitted by the OB stars in a galaxy of a given morphological class and the luminosity of the galaxy. In this case the ratio of the number of ionlzing photons emitted by the OB stars to the number emitted by the UV stars is the same for all galaxies of a given morphological class regardless of their individual luminosities. This ratio is estimated to be about 4 for Sb galaxies and to range from about 1.7 for SO galaxies to 26 for l galaxies. Using the knowledge of the rate of emission of ionizing photons, the equivalent widths of H alpha and STAO II! lambda 3727 in the integrated spectra of galaxies were calculated on the assumption that these galaxies have enough gas to absorb all the ionlzing radiation emitted by the hot stars. Some cases where ordinary galaxies have anomalously large amounts of ionlzed gas which cannot be produced by radiation from conventional hot stars are noted and discussed. (auth)

• Research Organization: Univ. of Michigan, Ann Arbor
• NSA Number: NSA-29-013645
• OSTI ID: 4378621
• Journal Information: Astron. Astrophys., v. 28, no. 1, pp. 63-70, Journal Name: Astron. Astrophys., v. 28, no. 1, pp. 63-70; ISSN AAEJA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

*COSMIC GASES-- IONIZATION
*GALAXIES-- LUMINOSITY
*STARS-- IONIZING RADIATIONS
*WHITE DWARF STARS-- IONIZING RADIATIONS
N56500* --Physics (Astrophysics & Cosmology)--Galaxies