Probing the Formation of Galaxy Clusters and their Members

2009 Fiscal Year Final Research Report

• Project/Area Number: 20740116
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Single-year Grants
• Research Field: Astronomy
• Research Institution: The Institute of Physical and Chemical Research
• Principal Investigator: OTA Kazuaki The Institute of Physical and Chemical Research, 牧島宇宙放射線研究室, 基礎科学特別研究員 (20462666)
• Project Period (FY): 2008 – 2009
• Keywords: 可視光天文学 / 観測的宇宙論 / 高赤方偏移銀河 / 銀河形成 / 銀河進化 / 観測天文学 / 銀河団 / 初期宇宙

Research Abstract

We compared volume and mass of the redshift z=6 (900 million years after the Big Bang) galaxy proto-cluster candidates we found with those of galaxy clusters at z<6 to examine how such physical properties have changed until today (z=0, 13.7 billion year after the Big Bang). We found that the z=6 proto-cluster has a larger volume but the masses are comparable. This implies that this z=6 object could be a progenitor and evolve to be a galaxy cluster seen in the present-day universe, assembling the mass toward the smaller volume. Also, our result suggests that the structure formation was already in a matured phase and formation of galaxy clusters were taking place even at the epoch as early as the 900 million year universe.