Nipoti, Carlo and Treu, Tommaso and Leauthaud, Alexie and Bundy, Kevin and Newman , Andrew B. and Auger, Matthew W. (2012) Size and velocity-dispersion evolution of early-type galaxies in a Λ cold dark matter universe. Monthly Notices of the Royal Astronomical Society, 422 (2). pp. 1714-1731. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20120611-153420942
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Early-type galaxies (ETGs) are observed to be more compact at z≳ 2 than in the local Universe. Remarkably, much of this size evolution appears to take place in a short ∼1.8 Gyr time span between z∼ 2.2 and 1.3, which poses a serious challenge to hierarchical galaxy formation models where mergers occurring on a similar time-scale are the main mechanism for galaxy growth. We compute the merger-driven redshift evolution of stellar mass M_* ∝ (1+z)^(a_M), half-mass radius inline image and velocity dispersion M_* ∝ (1+z)^(a_R) predicted by concordance Λ cold dark matter for a typical massive ETG in the redshift range z∼ 1.3–2.2. Neglecting dissipative processes, and thus maximizing evolution in surface density, we find −1.5 ≲a_M≲−0.6, −1.9 ≲a_R≲−0.7 and 0.06 ≲a_σ≲ 0.22, under the assumption that the accreted satellites are spheroids. It follows that the predicted z ∼ 2.2 progenitors of z ∼ 1.3 ETGs are significantly less compact (on average a factor of ∼2 larger R_e at given M*) than the quiescent galaxies observed at z≳ 2. Furthermore, we find that the scatter introduced in the size–mass correlation by the predicted merger-driven growth is difficult to reconcile with the tightness of the observed scaling law. We conclude that – barring unknown systematics or selection biases in the current measurements – minor and major mergers with spheroids are not sufficient to explain the observed size growth of ETGs within the standard model.
|Additional Information:||© 2012 The Authors. Monthly Notices of the Royal Astronomical Society. © 2012 RAS. We are grateful to Peter Behroozi and Richard Ellis for insightful comments on an earlier version of this manuscript. We thank Michael Boylan-Kolchin and Carlo Giocoli for helpful discussions. We acknowledge the CINECA Awards N. HP10C2TBYB (2011) and HP10CQFATD (2011) for the availability of high performance computing resources. CN is supported by the MIUR grant PRIN2008, TT by the Packard Foundation through a Packard Research Fellowship. We also acknowledge support by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan.|
|Subject Keywords:||galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: formation; galaxies: kinematics and dynamics; galaxies: structure|
|Official Citation:||Nipoti, C., Treu, T., Leauthaud, A., Bundy, K., Newman, A. B. and Auger, M. W. (2012), Size and velocity-dispersion evolution of early-type galaxies in a Λ cold dark matter universe. Monthly Notices of the Royal Astronomical Society, 422: 1714–1731. doi: 10.1111/j.1365-2966.2012.20749.x|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||12 Jun 2012 21:26|
|Last Modified:||12 Jun 2012 21:26|
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