# The contribution of starbursts and normal galaxies to infrared luminosity functions at z < 2

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Abstract : We present a parameter-less approach to predict the shape of the infrared (IR) luminosity function (LF) at redshifts $z \leq$ 2. It requires no tuning and relies on only three observables: (1) the redshift evolution of the stellar mass function for star-forming galaxies, (2) the evolution of the specific star formation rate (sSFR) of main-sequence galaxies, and (3) the double-Gaussian decomposition of the sSFR-distribution at fixed stellar mass into a contribution (assumed redshift- and mass-invariant) from main-sequence and starburst activity. This self-consistent and simple framework provides a powerful tool for predicting cosmological observables: observed IR LFs are successfully matched at all $z \leq$ 2, suggesting a constant or only weakly redshift-dependent contribution (8-14%) of starbursts to the star formation rate density. We separate the contributions of main-sequence and starburst activity to the global IR LF at all redshifts. The luminosity threshold above which the starburst component dominates the IR LF rises from log($L_{IR}$/$L_ \odot$) = 11.4 to 12.8 over 0 < z < 2, reflecting our assumed (1$+z)^{2.8}$-evolution of sSFR in main-sequence galaxies.
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### Citation

Mark T. Sargent, M. Béthermin, Emanuele Daddi, D. Elbaz. The contribution of starbursts and normal galaxies to infrared luminosity functions at z < 2. The Astrophysical journal letters, Bristol : IOP Publishing, 2012, 747 (2), pp.L31. ⟨10.1088/2041-8205/747/2/L31⟩. ⟨cea-00995654⟩

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