The two regimes of the cosmic sSFR evolution are due to spheroids and discs

Abstract

This paper aims at explaining the two phases in the observed specific star formation rate (sSFR), namely the high (>3/Gyr) values at z>2 and the smooth decrease since z=2. In order to do this, we compare to observations the specific star formation rate evolution predicted by well calibrated models of chemical evolution for elliptical and spiral galaxies, using the additional constraints on the mean stellar ages of these galaxies (at a given mass). We can conclude that the two phases of the sSFR evolution across cosmic time are due to different populations of galaxies. At z>2 the contribution comes from spheroids: the progenitors of present-day massive ellipticals (which feature the highest sSFR) as well as halos and bulges in spirals (which contribute with average and lower-than-average sSFR). In each single galaxy the sSFR decreases rapidly and the star formation stops in <1 Gyr. However the combination of different generations of ellipticals in formation might result in an apparent lack of strong evolution of the sSFR (averaged over a population) at high redshift. The z<2 decrease is due to the slow evolution of the gas fraction in discs, modulated by the gas accretion history and regulated by the Schmidt law. The Milky Way makes no exception to this behaviour.

8 pages, 5 figures, MNRAS accepted

References in corpus (6)

• Star Formation in AEGIS Field Galaxies since z=1.1 : The Dominance of Gradually Declining Star Formation, and the Main Sequence of Star-Forming Galaxies
• The Mass-Metallicity Relation at z~2
• The Stellar, Gas and Dynamical Masses of Star-Forming Galaxies at z~2
• Ages and Abundances of Red Sequence Galaxies as a Function of LINER Emission Line Strength
• Polarized Line Formation in Multi-dimensional Media. IV. A Fourier Decomposition Technique To Formulate The Transfer Equation With Angle-Dependent Partial Frequency Redistribution
• Are dry mergers of Ellipticals the way to reconcile model predictions with the downsizing?

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• A Predicted New Population of UV-faint Galaxies at z>4
• The impact of the Star Formation Histories on the SFR-M${}_{\ast }$ relation at z$\ge$2
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• Cosmic Star Formation: a simple model of the SFRD(z)