科研之友
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摘要
We report the first identification of a compact dense galaxy overdensity at z similar to 8 called A2744z8OD. A2744z8OD consists of eight Y-dropout galaxies behind Abell 2744 that were originally pinpointed by Hubble Frontier Fields studies. However, so far, no studies have derived the basic physical quantities of structure formation or made comparisons with theoretical models. We obtain a homogeneous sample of dropout galaxies at z similar to 8 from eight field data of Hubble legacy images that are as deep as the A2744z8OD data. Using the sample, we find that a galaxy surface overdensity value of A2744z8OD is very high delta similar or equal to 130, where delta is defined by an overdensity in a small circle of 6 '' (similar or equal to 30 physical kiloparsecs) radius. Because there is no such large delta value reported for high-z overdensities to date, A2744z8OD is a system that is clearly different from those found in previous high-z overdensity studies. In the galaxy vertical bar structure formation models of Henriques et al., there exists a very similar overdensity, Modelz8OD, that is made of eight model dropout galaxies at z similar to 8 in a 6 '' radius circle. Modelz8OD is a progenitor of a today's 10(14)M(circle dot) cluster, and more than half of the seven Modelz8OD galaxies are merged into the brightest cluster galaxy of the cluster. If Modelz8OD is a counterpart to. A2744z8OD, the models suggest that A2744z8OD would be part of a cluster core forming from a 10(14)M(circle dot) cluster that began star formation at z > 12.
- 出版日期2016-5-1
