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The origin of the enhanced metallicity of satellite galaxies.

Bahé, Y. M. and Schaye, J. and Crain, R. A. and McCarthy, I. G. and Bower, R. G. and Theuns, T. and McGee, S. L. and Trayford, J. W. (2017) 'The origin of the enhanced metallicity of satellite galaxies.', Monthly notices of the Royal Astronomical Society., 464 (1). pp. 508-529.


Observations of galaxies in the local Universe have shown that both the ionized gas and the stars of satellites are more metal-rich than of equally massive centrals. To gain insight into the connection between this metallicity enhancement and other differences between centrals and satellites, such as their star formation rates, gas content, and growth history, we study the metallicities of >3600 galaxies with Mstar > 1010  M⊙ in the cosmological hydrodynamical EAGLE 100 Mpc ‘Reference’ simulation, including ∼1500 in the vicinity of galaxy groups and clusters (M200 ≥ 1013 M⊙). The simulation predicts excess gas and stellar metallicities in satellites consistent with observations, except for stellar metallicities at Mstar ≲ 1010.2 M⊙ where the predicted excess is smaller than observed. The exact magnitude of the effect depends on galaxy selection, aperture, and on whether the metallicity is weighted by stellar mass or luminosity. The stellar metallicity excess in clusters is also sensitive to the efficiency scaling of star formation feedback. We identify stripping of low-metallicity gas from the galaxy outskirts, as well as suppression of metal-poor inflows towards the galaxy centre, as key drivers of the enhancement of gas metallicity. Stellar metallicities in satellites are higher than in the field as a direct consequence of the more metal-rich star-forming gas, whereas stripping of stars and suppressed stellar mass growth, as well as differences in accreted versus in situ star formation between satellites and the field, are of secondary importance.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:28 September 2016
Date deposited:02 March 2017
Date of first online publication:07 October 2016
Date first made open access:02 March 2017

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