H$alpha$ emission from the disks of spiral galaxies

Journal Article · Sun Feb 01 04:00:00 EST 1976 · Astrophys. J., v. 203, no. 3, pp. 587-592

DOI:https://doi.org/10.1086/154115· OSTI ID:4026674

Cohen, J G

Observations of the amount of H$alpha$ emission from the disks of 53 galaxies have been made using large entrance apertures so that the maximum possible fraction of the total area of the galaxy is included. These observations reveal a relationship between B--V color and H$alpha$ emission; for a given morphological type the bluer galaxies have more emission at H$alpha$. The effect of the strong emission lines on the colors is not sufficient to produce this trend. Furthermore, the H$alpha$ emission comes from discrete Hii regions ionized by starlight which are limited in the crudest approximation by the number of hot stars rather than the availability of gas. From the range in H$alpha$ emission, the ratio of hot stars to cooler stars corresponding to the observed range in B--V color is obtained. This is compared with a theoretical model by Searle, Sargent, and Bagnuolo which predicts B--V color as a function of the stellar luminosity function in the galaxy. The two separate methods of determining the change in ratio of hot-to-cool stars agree well. Further observational support is thus given to the models of Searle, Sargent, and Bagnuolo. (AIP)

• Research Organization: Kitt Peak National Observatory
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-030817
• OSTI ID: 4026674
• Journal Information: Astrophys. J., v. 203, no. 3, pp. 587-592, Journal Name: Astrophys. J., v. 203, no. 3, pp. 587-592; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

*GALAXIES-- LYMAN LINES
*H2 REGIONS-- LYMAN LINES
640105* --Physics Research--Astrophysics & Cosmology-- Galaxies
COLOR
EMISSION SPECTRA
EQUILIBRIUM
HYDROGEN
IONIZATION
LUMINOSITY
N56200 --Physics (Astrophysics & Cosmology)--Stars
N56500* --Physics (Astrophysics & Cosmology)--Galaxies
PHOTOMETRY
SPIRAL CONFIGURATION
ULTRAVIOLET RADIATION