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The central dark matter content of early-type galaxies: scaling relations and connections with star formation histories

Napolitano, Nicola R. ; Romanowsky, Aaron J. ; Tortora, Crescenzo

In: Monthly Notices of the Royal Astronomical Society, 2010, vol. 405, no. 4, p. 2351-2371

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    Titre
    • The central dark matter content of early-type galaxies: scaling relations and connections with star formation histories
    Auteur
    • Napolitano, Nicola R.. INAF - Osservatorio Astronomico di Capodimonte, Salita Moiariello, 16, 80131 Napoli, Italy
    • Romanowsky, Aaron J.. UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA
    • Tortora, Crescenzo. Universität Zürich, Institut für Theoretische Physik, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
    Type de document
    • Postprint
    Langue
    • Inglese
    Publié dans
    • Monthly Notices of the Royal Astronomical Society, 2010, vol. 405, no. 4, p. 2351-2371. Blackwell Publishing Ltd
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:303251
    Summary
    We examine correlations between masses, sizes and star formation histories for a large sample of low-redshift early-type galaxies, using a simple suite of dynamical and stellar population models. We confirm an anticorrelation between the size and stellar age and go on to survey for trends with the central content of dark matter (DM). An average relation between the central DM density and galaxy size of 〈ρDM〉∝R−2eff provides the first clear indication of cuspy DM haloes in these galaxies - akin to standard Λ cold dark matter haloes that have undergone adiabatic contraction. The DM density scales with galaxy mass as expected, deviating from suggestions of a universal halo profile for dwarf and late-type galaxies. We introduce a new fundamental constraint on galaxy formation by finding that the central DM fraction decreases with stellar age. This result is only partially explained by the size-age dependencies, and the residual trend is in the opposite direction to basic DM halo expectations. Therefore, we suggest that there may be a connection between age and halo contraction and that galaxies forming earlier had stronger baryonic feedback, which expanded their haloes, or lumpier baryonic accretion, which avoided halo contraction. An alternative explanation is a lighter initial mass function for older stellar populations