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arXiv · 1202.0971

Size and velocity-dispersion evolution of early-type galaxies in a Lambda cold dark matter universe

C. Nipoti·T. Treu·A. Leauthaud·K. Bundy·A. B. Newman·M. W. Auger
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Abstract

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 z=1.3, which poses a serious challenge to hierarchical galaxy formation models where mergers occurring on a similar timescale are the main mechanism for galaxy growth. We compute the merger-driven redshift evolution of stellar mass Mstar\propto(1+z)^aM, half-mass radius Re\propto(1+z)^aR and velocity-dispersion sigma0\propto(1+z)^asigma predicted by concordance Lambda 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 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.

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C. Nipoti, T. Treu, A. Leauthaud, K. Bundy, A. B. Newman, M. W. Auger. 2012-04-02. Size and velocity-dispersion evolution of early-type galaxies in a Lambda cold dark matter universe. https://doi.org/10.1111/j.1365-2966.2012.20749.x

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