宇宙平均色-星等关系散射的演化：证明与椭圆星系正在形成的一致性
The evolution of the scatter of the cosmic average color-magnitude relation: Demonstrating consistency with the ongoing formation of elliptical galaxies
摘要：
我们提出的第一个测量的宇宙平均早期型星系的颜色-星等关系（CMR）从z=1到今天的散射的演变，发现它是一致的模型中，星系不断被添加到红色序列，通过截断恒星形成在蓝色云星系。我们使用了超过700个红色序列的样本，结构选择的早期类型星系（定义为Sersic指数>2.5），红移0<z<1，来自扩展钱德拉深场南方（173个星系）和斯隆数字巡天（550个星系），构建了精确到<0.04等的静止框架U-V颜色。我们发现宇宙平均早型星系的CMR在静止坐标系U-V色中的散射在0.05<z<0.75时约为0.1mag，在z=1时略高。我们将这些观测结果与一个模型进行了比较，在该模型中，新的红色序列星系以与观测到的数量密度演化相匹配的速率不断添加，并发现该模型预测了正确的巨磁共振散射及其演化。此外，这个模型预测大约正确的数量密度的“蓝色球状体”-结构早期型星系与蓝色的颜色-虽然有相当大的模型依赖性。因此，我们的结论是，无论是早期型星系人口的数量密度和颜色的演变描绘了一个一致的图片，早期型星系人口增长显着之间的z=1和现在的一天，通过淬火的恒星形成在蓝云星系。
英文摘要：
We present first measurements of the evolution of the scatter of the cosmic average early-type galaxy color-magnitude relation (CMR) from z=1 to the present day, finding that it is consistent with models in which galaxies are constantly being added to the red sequence through truncation of star formation in blue cloud galaxies. We used a sample of over 700 red sequence, structurally-selected early-type galaxies (defined to have Sersic index >2.5) with redshifts 0<z<1 taken from the Extended Chandra Deep Field South (173 galaxies) and the Sloan Digital Sky Survey (550 galaxies), constructing rest-frame U-V colors accurate to <0.04mag. We find that the scatter of the CMR of cosmic average early-type galaxies is ~0.1mag in rest-frame U-V color at 0.05<z<0.75, and somewhat higher at z=1. We compared these observations with a model in which new red sequence galaxies are being constantly added at the rate required to match the observed number density evolution, and found that this model predicts the correct CMR scatter and its evolution. Furthermore, this model predicts approximately the correct number density of `blue spheroids' - structurally early-type galaxies with blue colors - albeit with considerable model dependence. Thus, we conclude that both the evolution of the number density and colors of the early-type galaxy population paint a consistent picture in which the early-type galaxy population grows significantly between z=1 and the present day through the quenching of star formation in blue cloud galaxies.
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