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The Star Formation Histories of Local Galaxies: Continuous or Intermittent?

Guinevere Kauffmann·Stephane Charlot·Michael L. Balogh
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Abstract

We explore a model in which efficient star formation in galaxies is triggered by merging satellites. We show that the merger/interaction rates predicted by hierarchical galaxy formation models depend strongly on galaxy mass. If a merger of a satellite larger than 1% the mass of the primary triggers efficient star formation, low-mass dwarf galaxies experience strong bursts separated by quiescent periods lasting several Gyr. Massive galaxies, such as our own Milky Way, are perturbed by a 1% satellite every few hundred million years, and thus have fluctuating, but relatively continuous star formation histories. We study the spectral signatures of a population of galaxies undergoing intermittent star formation by combining the models with the latest version of the Bruzual & Charlot spectral synthesis code. We concentrate on spectral indicators that are sensitive primarily to stellar age, rather than to metallicity and extinction. We show that if a population undergoes intermittent rather than continuous star formation, the signatures of the bursts should be evident from the observed dispersion in the star formation rates, H-delta equivalent widths and gas mass fractions of galaxies with 4000 Angstrom break strengths indicative of recent or ongoing star formation.

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Guinevere Kauffmann, Stephane Charlot, Michael L. Balogh. 2001-03-08. The Star Formation Histories of Local Galaxies: Continuous or Intermittent?. https://arxiv.org/abs/astro-ph/0103130

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