2013 Fiscal Year Annual Research Report
次世代深宇宙探査で明らかにする初期銀河形成と宇宙再電離
| Project/Area Number |
13F03016
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| Research Institution | The University of Tokyo |
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Principal Investigator |
大内 正己 東京大学, 宇宙線研究所, 准教授
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| Co-Investigator(Kenkyū-buntansha) |
YUMA Suraphong 東京大学, 宇宙線研究所, 外国人特別研究員
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| Keywords | 銀河進化 / 高赤方偏移 |
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| Research Abstract |
During FY2013, we conducted the first systematic search for galaxies with spatially extended [OII] λ3726, 3729 emission at z=1.2 dubbed "[OII] blobs" by using available deep Suprime-Cam data in the Subaru/XMM-Newton Deep survey (SXDS) field. We discovered a giant blob (OIIB1) with spatial extent over 75kpc and identified a total of 12 [OII] blobs with a size larger than 30kpc. The extension of oxygen emission beyond the stellar component of a galaxy is considered to be due to strong outflow driven by AGN and/or stellar feedback. The optical spectrum of OIIB1 presents [NeV] 3426 emission, indicating that this object host an obscured type-2 active galactic nucleus (AGN). The presence of gas outflow in the giant [OII] blob is confirmed by FeII2587 absorption and FeII*2613 emission lines with outflow velocity of 500-600 km/s. This suggests that its heating source is AGN feedback or associated shock excitation rather than supernovae produced by starburst. As the first systematic search, we are able to estimate the number density of extended oxygen-line emitting galaxies, i.e. [OII] blobs, for the first time. The number density of OIIB1-type giant blobs is 5x10^<-6> Mpc^<-3>, which is comparable to that of AGNs driving outflow at the similar redshift. Meanwhile, the number density of small [OII] blobs implies that 3% of star-forming galaxies at z=1 are quenching star formation through outflow involving extended [OII] emission.
This is the first discovery of large physical extents of energetic oxygen-gas outflows driven by AGN or star formation. We published one outstanding paper on this study and announced the press release last December. The press release appeared on UTokyo research, ICRR, and Subaru telescope webpage and received impressive attentions from various news websites both inside and outside Japan.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Most part of the research plan is in impressive progress. We published one paper on the discovery of oxygen blobs at z～1.2, a good laboratory to understand the gas outflow process of galaxies at the early universe. However, as the Hyper Suprime-Cam (HSC) survey has just started in March 2014, we did not have time to get into the HSC data yet. The study with data from HSC survey as written in the research plan will be conducted in FY2014.
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| Strategy for Future Research Activity |
Following our discovery of [OII] blobs, we are preparing another paper on their evolution using the Suprime-Cam data. After that, we will get back to the HSC data analysis and conduct the research using unprecedentedly large data provided by the HSC survey.
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