The star-formation history of the Universe from the stellar populations of nearby galaxies

Abstract

The determination of the star-formation history of the Universe is a key goal of modern cosmology, as it is crucial to our understanding of how galactic structures form and evolve. Observations of young stars in distant galaxies at different times in the past have indicated that the stellar birthrate peaked some eight billion years ago before declining by a factor of around ten to its present value. Here we report an analysis of the 'fossil record' of the current stellar populations of 96,545 nearby galaxies, from which we obtained a complete star-formation history. Our results broadly support those derived from high-redshift galaxies. We find, however, that the peak of star formation was more recent--around five billion years ago. We also show that the bigger the stellar mass of the galaxy, the earlier the stars were formed, which indicates that high- and low-mass galaxies have very different histories.

Perspectives of high-energy neutrino astronomy

“…For a Einstein-De Sitter universe (Ω m = 1, Ω Λ = 0) with no evolution for the sources one has ξ = 0.4, for the "concordance model" cosmology (Ω m = 0.3, Ω Λ = 0.7) this becomes ξ = 0.53. For the same concordance model cosmology, if it is assumed that the cosmic time dependence of the neutrino injection is similar to the one fitted to the star-formation history [25,26], one obtains ξ(SFR) ≃ 3.0, for a time dependence equal to the one fitted to the AGN luminosity evolution [27] one finds ξ(AGN) ≃ 2.2. If we consider the power and energy density not bolometric, but only integrated above the threshold energy E min , the redshift effects depend on the shape of the injection spectrum.…”

Star formation sustained by gas accretion

“…In a complementary work, Heavens et al (2004) analyzed the fossil record of the current stellar populations in nearly 10 5 nearby galaxies. This allowed them to reconstruct the SFR density along the age of the universe for galaxies of different masses independently.…”

“…The bulk of the SFR at z 0.5 comes from galaxies with present-day stellar masses in the range 3-30×10 10 M . The figure was taken from Heavens et al (2004) history differs according to the (present) galaxy mass so that the larger the stellar mass the earlier their stars were formed. High-and low-mass galaxies have very different SF histories.…”

THE SFR–M* RELATION AND EMPIRICAL STAR FORMATION HISTORIES FROM ZFOURGE AT 0.5 < z < 4*

“…However, inferring star formation and mass growth histories of individual galaxies is a non-trivial undertaking, and a variety of methods have been used in the literature. One class of methods involves "archeological" studies of nearby galaxies, either by studying resolved stellar populations or by detailed modeling of high signal-to-noise spectra (e.g., Dolphin et al 2003;Heavens et al 2004;Thomas et al 2005). However degeneracies in age, metallicity, and extinction complicate modeling with these techniques.…”