科研之友
微信
新浪微博
Facebook
分享链接
摘要
We performed a systematic spectroscopic observation of a protocluster at z = 6.01 in the Subaru Deep Field. We took spectroscopy for all 53 i%26apos; dropout galaxies down to z%26apos; = 27.09 mag in/around the protocluster region. From these observations, we confirmed that 28 galaxies are at z similar to 6, 10 of which are clustered in a narrow redshift range of Delta z %26lt; 0.06. To trace the evolution of this primordial structure, we applied the same i%26apos; dropout selection and the same overdensity measurements used in the observations to a semi-analytic model built upon the Millennium Simulation. We obtain a relation between the significance of overdensities observed at z similar to 6 and the predicted dark matter halo mass at z = 0. This protocluster with 6 sigma overdensity is expected to grow into a galaxy cluster with a mass of similar to 5 x 10(14) M-circle dot at z = 0. Ten galaxies within 10 comoving Mpc of the overdense region can, with more than an 80% probability, merge into a single dark matter halo by z = 0. No significant differences appeared in UV and Ly alpha luminosities between the protocluster and field galaxies, suggesting that this protocluster is still in the early phase of cluster formation before the onset of any obvious environmental effects. However, further observations are required to study other properties, such as stellar mass, dust, and age. We do find that galaxies tend to be in close pairs in this protocluster. These pair-like subgroups will coalesce into a single halo and grow into a more massive structure. We may witness an onset of cluster formation at z similar to 6 toward a cluster as seen in local universe.
- 出版日期2014-9-1
- 单位中国科学院国家天文台
