Mass downsizing and ``top-down'' assembly of early-type galaxies
Mass downsizing and ``top-down'' assembly of early-type galaxies
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DOI：
10.1051/0004-6361:20065155
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发表时间：
2006-05
影响因子：
6.5
通讯作者：
A. Cimatti;E. Daddi;A. Renzini
中科院分区：
文献类型：
--
作者：
A. Cimatti;E. Daddi;A. Renzini
目标。我们提出了一种新的分析早期类型星系(ETG)的静止标架B带COMBO-17和DEEP2光度函数(LF)作为光度和质量的函数。我们的目标是从$z\sim1$开始对ETG的演化施加新的严格约束。方法：研究方法。我们在假设纯光度演化的前提下，对LF(Z)的光度变暗进行了修正。然而，我们没有依赖于恒星布居合成模型的假设，而是采用了从场和星团质量ETG的基面演化得到的经验光度变暗率。结果。我们的结果表明，ETG种群的进化量取决于所考虑的光度和质量的范围。虽然发光(大质量)ETG的数密度在$ZSIM 0.8之后几乎不变，但发光(大质量)ETG的数密度几乎不变，这是由于质量小于10^{11}~M_(\ODOT)的星系中恒星形成的逐渐熄灭导致ETG“红色序列”的逐渐增多所致。每一次红移都有一个临界值，在这个临界值之上，几乎所有的ETG似乎都已就位，这很适合现在流行的“瘦身”情景。然而，“缩小规模”似乎并不局限于恒星的形成，但这个概念可能必须扩展到质量集合本身，因为最大质量星系的形成先于质量较小的星系的形成。即使最新的理论模拟成功地再现了恒星形成过程中的“缩小尺度”，这种进化趋势也无法被复制。
Aims. We present a new analysis of the rest-frame B -band COMBO-17 and DEEP2 luminosity functions (LFs) of early-type galaxies (ETGs) as a function of luminosity and mass. Our aim is to place new stringent constraints on the evolution of ETGs since $z\sim1$. Methods. We correct the LF( z ) data for the luminosity dimming assuming pure luminosity evolution. However, instead of relying on stellar population synthesis model-dependent assumptions, we adopt the empirical luminosity dimming rate derived from the evolution of the Fundamental Plane of field and cluster massive ETGs. Results. Our results show that the amount of evolution for the ETG population depends critically on the range of luminosity and masses considered. While the number density of luminous (massive) ETGs with $M_{B}(z=0) 10^{11}$ $M_{\odot}$) is nearly constant since $z\sim 0.8$, less luminous galaxies display a deficit which grows with redshift and that can be explained with a gradual population of the ETG “red sequence” by the progressive quenching of star formation in galaxies less massive than ${\sim} 10^{11}~ M_{\odot}$. At each redshift there is a critical mass above which virtually all ETGs appear to be in place, and this fits well in the now popular “downsizing” scenario. However, “downsizing” does not appear to be limited to star formation, but the concept may have to be extended to the mass assembly itself as the build-up of the most massive galaxies preceeds that of the less massive ones. This evolutionary trend is not reproduced by the most recent theoretical simulations even when they successfully reproduce “downsizing” in star formation.