The fading of young stellar populations and the luminosity functions of dwarf, irregular, and starburst galaxies

David W. Hogg, E. S. Phinney

    Research output: Contribution to journalArticle


    Dwarf, irregular, and infrared-luminous starburst galaxies are all known to have "steep" luminosity functions with faint-end behavior roughly φ(L) ∝ L-1.8. This form is exactly what is expected if the luminosities of these objects fade with time as L ∝ t-1.3, because the objects spend more time at low luminosities than high, even if they form with a wide range of initial masses. Models of young stellar populations show this fading behavior when the star formation has occurred in a single, short, recent burst. Steep luminosity functions therefore do not require steep mass functions if the galaxies are powered by fading bursts. The local galaxy Hα luminosity function-which is less steep than L-1.8 - is also well fitted by this mechanism, because ionizing photon flux fades much more quickly than broadband optical luminosity. An age-luminosity relation and a wavelength dependence of the luminosity function are both predicted. In the context of this mechanism, the slope of the luminosity function provides a constraint on the stellar initial mass function in the bursts.

    Original languageEnglish (US)
    Pages (from-to)L95-L99
    JournalAstrophysical Journal
    Issue number2 PART II
    StatePublished - Jan 1 1997



    • Galaxies: luminosity function, mass function
    • Galaxies: starburst
    • Galaxies: stellar content
    • Infrared: galaxies
    • Stars: luminosity function, mass function

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this