Observational study of extremely emission line galaxies: implication for early galaxy formation and the cosmic reionization

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K14257
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Astronomy
• Research Institution: National Astronomical Observatory of Japan
• Principal Investigator: Onodera Masato 国立天文台, ハワイ観測所, 助教 (40778396)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 銀河進化 / 銀河形成 / 宇宙再電離

Outline of Final Research Achievements

We carried out a systematic search of star-forming galaxies at 3<z<3.7 with intense [OIII]λ5007 emission line. Sample is selected based on excesses in the K-band flux due to the emission lines, and we selected 240 objects. We spectroscopically identified 19 objects by Subaru/MOIRCS observation and found that they are indeed at z>3 with intense [OIII] emission lines. By comparing physical properties for them, it is suggested that they are young and low metallicity galaxies with bursty star formation. We also find that their hydrogen ionizing photon production efficiencies are higher than the widely used canonical values by a factor of two or more.

Free Research Field

銀河天文学

Academic Significance and Societal Importance of the Research Achievements

本研究において、極めて強い輝線を示す赤方偏移3を越える銀河を広帯域フィルターのデータのみによって選択できることを示した。狭帯域フィルターによるサーベイはその利点はあるものの、広帯域フィルターを用いた場合は一度に観測できる宇宙の体積がはるかに大きいため、相補的な手法を確立させた点で意義がある。また、これらの天体のライマン連続光の高い生成効率を再現するには、広く用いられている恒星種族合成モデルに対して修正が必要なことが示唆され、極端な天体を用いたことで理論についての制限を与えた点でも学術的意義がある。