Reconciling a significant hierarchical assembly of massive early-type galaxies at z<~1 with mass downsizing

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Eliche Moral, María del Carmen
Prieto, Mercedes
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Springer-Verlag Berlin
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Hierarchical models predict that massive early-type galaxies (mETGs) are the latest systems to be in place into the cosmic scenario (at z<~0.5), conflicting with the observational phenomenon of galaxy mass downsizing, which poses that the most massive galaxies have been in place earlier that their lower-mass counterparts (since z~0.7). We have developed a semi-analytical model to test the feasibility of the major-merger origin hypothesis for mETGs, just accounting for the effects on galaxy evolution of the major mergers strictly reported by observations. The most striking model prediction is that very few present-day mETGs have been really in place since z~1, because ~90% of the mETGs existing at z~1 are going to be involved in a major merger between z~1 and the present. Accounting for this, the model derives an assembly redshift for mETGs in good agreement with hierarchical expectations, reproducing observational mass downsizing trends at the same time.
© Springer-Verlag Berlín Heidelberg 2011. Symposium 2 of JENAM (2. 2010. Lisbon/Portugal). Supported by the Spanish Ministry of Science and Innovation (MICINN) under project AYA2009-10368 and by the Madrid Regional Government through the AstroMadrid Project (CAM S2009/ESP-1496). Funded by the Spanish MICINN under the Consolider-Ingenio 2010 Program grant CSD2006-00070: ”First Science with the GTC”.
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