Size and velocity-dispersion evolution of early-type galaxies in a Λ cold dark matter universe
Size and velocity-dispersion evolution of early-type galaxies in a Λ cold dark matter universe
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α冷暗物质宇宙中早期型星系的大小和速度色散演化
DOI：
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
M. Auger
中科院分区：
文献类型：
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作者：
C. Nipoti;T. Treu;A. Leauthaud;K. Bundy;A. Newman;M. Auger
早型星系（ETG）在z = 2时被观测到比在本地宇宙中更紧凑。值得注意的是，这种大小的演化似乎发生在z = 2.2和1.3之间的短时间内，这对星系形成模型提出了严重的挑战，其中在类似的时间尺度上发生的合并是星系生长的主要机制。计算了红移范围z = 1.3-2.2的典型大质量ETG的质量M_*<$（1+z）^（a_M）、半质量半径线内像和速度色散M_*<$（1+z）^（a_R）的并合驱动红移演化。忽略耗散过程，从而使表面密度的演化最大化，在假设吸积的卫星是球体的情况下，我们得到−1.5 <$a_M <$$> −0.6，−1.9 <$a_R <$$> −0.7和0.06 <$a_σ <$0.22。因此，预测的z <$1.3 ETG的z <$2.2祖先明显不如在z <$2观测到的静止星系紧凑（在给定M* 时，平均R_e大2.2倍）。此外，我们发现，预测的合并驱动的增长的尺寸-质量相关性中引入的分散是难以调和的紧密性所观察到的标度律。我们的结论是，在目前的测量中，除非未知的系统学或选择偏差，否则与球体的次要和主要合并不足以解释标准模型中观察到的ETG尺寸增长。
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.
影响因子：
8.7
作者：
Komatsu, E.;Smith, K. M.;Wright, E. L.
通讯作者：
Wright, E. L.
DOI：
10.1088/0004-637x/744/1/63
发表时间：
2011-06
期刊：
The Astrophysical Journal
影响因子：
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作者：
L. Oser;T. Naab;J. Ostriker;P. Johansson
通讯作者：
L. Oser;T. Naab;J. Ostriker;P. Johansson