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Hα emission from the disks of spiral galaxies

Cohen, Judith G. (1976) Hα emission from the disks of spiral galaxies. Astrophysical Journal, 203 . pp. 587-592. ISSN 0004-637X. doi:10.1086/154115.

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Observations of the amount of Ha 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 Ha emission; for a given morphological type the bluer galaxies have more emission at Ha. The effect of the strong emission lines on the colors is not sufficient to produce this trend. Furthermore, the Ha emission comes from discrete H II 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 Ha emission, we obtain the ratio of hot stars to cooler stars corresponding to the observed range in B - V color. We then compare this 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. We thus give further observational support to the models of Searle, Sargent, and Bagnuolo.

Item Type:Article
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Cohen, Judith G.0000-0002-8039-4673
Alternate Title:H-alpha emission from the disks of spiral galaxies
Additional Information:© American Astronomical Society • Provided by the NASA Astrophysics Data System. Received 1975 May 29; revised 1975 July 7. We thank A. Gomez for significant help in obtaining the observations, and G. Grasdalen for measuring a galaxy in the UBV system.
Subject Keywords:galactic: structure - galaxies: photometry- galaxies: stellar content -nebulae: general
Record Number:CaltechAUTHORS:20190529-161902761
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95904
Deposited By: George Porter
Deposited On:31 May 2019 15:11
Last Modified:16 Nov 2021 17:16

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