The [α/Fe] ratios of very metal-poor stars within the integrated galactic initial mass function theory

Recchi, S.; Calura, F.; Kroupa, P.; Gibson, B. K.

Abstract

The aim of this paper is to quantify the amplitude of the predicted plateau in [α/Fe] ratios associated with the most metal-poor stars of a galaxy. We assume that the initial mass function (IMF) in galaxies is steeper if the star formation rate (SFR) is low – as per the integrated galactic initial mass function (IGIMF) theory. A variant of the theory, in which the IGIMF depends upon the metallicity of the parent galaxy, is also considered. The IGIMF theory predicts low [α/Fe] plateaus in dwarf galaxies, characterized by small SFRs. The [α/Fe] plateau is up to 0.7 dex lower than the corresponding plateau of the Milky Way. For a universal IMF one should expect instead that the [α/Fe] plateau is the same for all the galaxies, irrespective of their masses or SFRs. Assuming a strong dependence of the IMF on the metallicity of the parent galaxy, dwarf galaxies can show values of the [α/Fe] plateau similar to those of the Milky Way, and almost independent of the SFR. The [Mg/Fe] ratios of the most metal-poor stars in dwarf galaxies satellites of the Milky Way can be reproduced either if we consider metallicity-dependent IMFs or if the early SFRs of these galaxies were larger than we presently think. Present and future observations of dwarf galaxies can help disentangle between these different IGIMF formulations.

Citation

Recchi, S., Calura, F., Kroupa, P., & Gibson, B. K. (2014). The [α/Fe] ratios of very metal-poor stars within the integrated galactic initial mass function theory. Monthly notices of the Royal Astronomical Society, 437(1), 994-1008. https://doi.org/10.1093/mnras/stt1971

• Acceptance Date: Oct 11, 2013
• Online Publication Date: Nov 14, 2013
• Publication Date: Jan 1, 2014
• Deposit Date: Apr 14, 2016
• Publicly Available Date: Apr 14, 2016
• Journal: Monthly notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 437
• Issue: 1
• Pages: 994-1008
• DOI: https://doi.org/10.1093/mnras/stt1971
• Keywords: Stars : abundances; Stars : luminosity function, mass function; Supernovae : general; Galaxies : dwarf; Galaxies : evolution; Galaxies : star clusters : general
• Public URL: https://hull-repository.worktribe.com/output/436118
• Publisher URL: http://mnras.oxfordjournals.org/content/437/1/994
• Additional Information: This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
• Contract Date: Apr 14, 2016