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Recycled stellar ejecta as fuel for star formation and implications for the origin of the galaxy mass-metallicity relation.

Segers, M. C. and Crain, R. A. and Schaye, J. and Bower, R. G. and Furlong, M. and Schaller, M. and Theuns, T. (2016) 'Recycled stellar ejecta as fuel for star formation and implications for the origin of the galaxy mass-metallicity relation.', Monthly notices of the Royal Astronomical Society., 456 (2). pp. 1235-1258.


We use cosmological, hydrodynamical simulations from the Evolution and Assembly of GaLaxies and their Environments and OverWhelmingly Large Simulations projects to assess the significance of recycled stellar ejecta as fuel for star formation. The fractional contributions of stellar mass-loss to the cosmic star formation rate (SFR) and stellar mass densities increase with time, reaching 35 and 19 per cent, respectively, at z = 0. The importance of recycling increases steeply with galaxy stellar mass for M* < 1010.5 M⊙, and decreases mildly at higher mass. This trend arises from the mass dependence of feedback associated with star formation and AGN, which preferentially suppresses star formation fuelled by recycling. Recycling is more important for satellites than centrals and its contribution decreases with galactocentric radius. The relative contribution of asymptotic giant branch (AGB) stars increases with time and towards galaxy centres. This is a consequence of the more gradual release of AGB ejecta compared to that of massive stars, and the preferential removal of the latter by star formation-driven outflows and by lock up in stellar remnants. Recycling-fuelled star formation exhibits a tight, positive correlation with galaxy metallicity, with a secondary dependence on the relative abundance of alpha elements (which are predominantly synthesized in massive stars), that is insensitive to the subgrid models for feedback. Hence, our conclusions are directly relevant for the origin of the mass–metallicity relation and metallicity gradients. Applying the relation between recycling and metallicity to the observed mass–metallicity relation yields our best estimate of the mass-dependent contribution of recycling. For centrals with a mass similar to that of the Milky Way, we infer the contributions of recycled stellar ejecta to the SFR and stellar mass to be 35 and 20 per cent, respectively.

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Publisher statement:This article has been published in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:29 October 2015
Date deposited:07 April 2016
Date of first online publication:23 December 2015
Date first made open access:No date available

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