On the buildup of massive early-type galaxies at z≲1 I. Reconciling their hierarchical assembly with mass downsizing



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Eliche Moral, María del Carmen and Prieto, M. and Gallego Maestro, Jesús and Barro, Guillermo and Zamorano Calvo, Jaime and López Sanjuan, C. and Balcells, M. and Guzmán, R. and Muñoz Mateos, J. C. (2010) On the buildup of massive early-type galaxies at z≲1 I. Reconciling their hierarchical assembly with mass downsizing. Astronomy and astrophysics, 519 . ISSN 0004-6361

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Official URL: http://dx.doi.org/10.1051/0004-6361/201014770


Context. Several studies have tried to ascertain whether the increase in abundance of the early-type galaxies (E-S0a's) with time is mainly due to major mergers, but have reached opposite conclusions. Aims. We have tested it directly through semi-analytical modelling, quantifying the possible contribution of the observed major mergers to the evolution of the high-mass end of the galaxy luminosity function (LF). Methods. The model analyses the backwards-in-time evolution of the massive early-type galaxies with log(M_*/M_⨀) > 11 at z∼0 (mETGs) under the hypothesis that each major merger leads to an early-type galaxy. The model considers only the major mergers strictly reported by observations at each redshift and assumes that gas-rich major mergers experience transitory phases as dust-reddened, star-forming galaxies (DSFs). Results. The model is able to reproduce the observed evolution of the galaxy LFs at z ≲ 1 simultaneously for different rest-frame bands (B, I, and K) and for different selection criteria on colour and morphology. It also provides a framework in which apparently contradictory results on the recent evolution of the LF of massive red galaxies can be reconciled, just considering that observed samples of red galaxies can be significantly contaminated by DSFs. The model proves that it is feasible to build up ∼50-60% of the present-day number density of mETGs at z≲1 through the coordinated action of wet, mixed, and dry major mergers, fulfilling global trends that are in general agreement with mass downsizing. The bulk of this assembly takes place during ∼1 Gyr elapsed at 0.8 < z < 1, providing a straightforward explanation for the observed fact that redshift z ∼ 0.8 is a transition epoch in the formation of mETGs. The gas-rich progenitors of these recently assembled mETGs reproduce the observed excess by a factor of ∼4-5 of late-type galaxies at 0.8 < z < 1 naturally, as compared to pure luminosity evolution (PLE) models. Conclusions. The model suggests that major mergers have been the main driver for the observed mass migration from the massive end of the blue galaxy cloud to that of the red sequence in the past ∼8 Gyr.

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© ESO 2010. The authors want to thank the anonymous referee for useful suggestions that clearly improved the paper. We wish to acknowledge J. P. Gardner for making its NCMOD code publicly available, and Antonio Benítez for interesting discussions and comments. Supported by the Spanish Programa Nacional de Astronomía y Astrofísica, under projects AYA2006-02358, AYA2009-10368, and AYA2006-12955. MCEM acknowledges support from the Madrid Regional Government through the ASTRID Project (S0505/ESP-0361), for development and exploitation of astronomical instrumentation (http://www.astrid-cm.org/). Partially funded by the Spanish MICINN under the Consolider-Ingenio 2010 Program grant CSD2006-00070: "First Science with the GTC" (http://www.iac.es/consolider-ingenio-gtc/).

Uncontrolled Keywords:Star-forming galaxies; Hubble-space-telescope; Digital sky survey; Post-starburst galaxies; Extremely red galaxies; High-redshift galaxies; VLT deep survey; Ultraluminous infrared galaxies; Sight velocity distributions; Morphological K-correction
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:33855
Deposited On:30 Oct 2015 14:30
Last Modified:10 Dec 2018 15:05

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