2016 Fiscal Year Annual Research Report
Halo assembly bias systematics in interpreting cosmic acceleration
Publicly Offered Research
| Project Area | Why does the Universe accelerate? - Exhaustive study and challenge for the future - |
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| Project/Area Number |
16H01089
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| Research Institution | The University of Tokyo |
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Principal Investigator |
MORE Surhud 東京大学, カブリ数物連携宇宙研究機構, 特任助教 (00646044)
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| Project Period (FY) |
2016-04-01 – 2018-03-31
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| Keywords | Stimulating / puzzling |
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| Outline of Annual Research Achievements |
The main goal of the project was to explore halo assembly bias and its effects on probes of cosmic acceleration. In FY 2016, we published a paper on the observational detection of halo assembly bias using optically selected cluster samples, improving on the previous results of Miyatake et al. 2016. We also presented a detection of the halo edges or the splashback radius of these galaxy clusters. These two results have generated a lot of enthusiasm in the community as the halo assembly bias appeared to be too large compared to expectations while the splashback radius appeared to be smaller by about 20 percent. One of the worries expressed were projection effects in optical galaxy cluster selection, so I had to spend the rest of the year trying to understand these projection effects. No credible mock galaxy catalogs existed for this purpose, and the cluster selection algorithm is not publicly available. So I have made progress on these fronts during this year.
I now have much cleaner evidence that the large assembly bias is unfortunately due to projections, and we are currently exploring ways to circumvent this problem (we have ideas which may work but are currently being tested with simulations). In the meanwhile I have also looked at other properties of the brightest galaxies in these clusters to find evidence for properties which can give a clean split for assembly bias, and which are less affected by projection systematics.I expect to write a paper on this during this year.
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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
This is the first time anyone has ever tried to present measurements of halo assembly bias on cluster scales and the halo edges. We have therefore faced some head winds due to mocks of galaxies not being available, as well as the cluster finding algorithms not being publicly available. I am trying my best to tackle these issues.
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| Strategy for Future Research Activity |
As a plan for the research in the next FY, we are investigating variety of galaxy cluster properties that are less affected by projection effects and which could be used to detect halo assembly bias. We also have a novel idea of using only the perpendicular mode of the large scale structure to detect halo assembly bias, which we are currently testing with simulations. We have indications that the level of assembly bias seen decreases and becomes more consistent withexpectations.
We are also in the process of exploring the effects of projection on the edges of galaxy clusters, or the splashback radius. To reduce the effect of projections, I will also be studying the splashback radius for clusters selected by Sunyaev-Zeldovich surveys or using Xray surveys.
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Research Products
(9 results)
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[Journal Article] Interpreting the Strongly Lensed Supernova iPTF16geu: Time Delay Predictions, Microlensing, and Lensing Rates2017
Author(s)
More, A., Suyu, S.H., Ogur, M., More, S. and Lee, C.-H.
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Journal Title
Astrophysical Journal Letters
Volume: 835
Pages: L25
DOI
Peer Reviewed / Int'l Joint Research
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[Journal Article] Detection of the Splashback Radius and Halo Assembly Bias of Massive Galaxy Clusters2016
Author(s)
More, S., Miyatake, H., Takada, M., Diemer, B., Kravtsov, A.V. , Dalal, N.K., More, A., Murata, R., Mandelbaum, R., Rozo, E. , Rykoff, E.S., Oguri, M. and Spergel, D. N.
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Journal Title
The Astrophysical Journal
Volume: 825
Pages: 39
DOI
Peer Reviewed / Int'l Joint Research
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[Journal Article] Strong bimodality in the host halo mass of central galaxies from galaxy-galaxy lensing2016
Author(s)
Mandelbaum, R., Wang, W., Zu, Y., White, S., Henriques, B. and More, S.
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Journal Title
MNRAS
Volume: 457
Pages: 3200-3218
DOI
Peer Reviewed / Int'l Joint Research
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[Journal Article] Evolution of Stellar-to-Halo Mass Ratio at z = 0 - 7 Identified by Clustering Analysis with the Hubble Legacy Imaging and Early Subaru/Hyper Suprime-Cam Survey Data2016
Author(s)
Harikane, Y., Ouchi, M., Ono, Y., More, S., Saito, S., Lin, Y.-T., Coupon, J., Shimasaku, K., Shibuya, T., Price, P.A., Lin, L., Hsieh, B.-C., Ishigaki, M., Komiyama, Y., Silverman, J., Takata, T., Tamazawa, H. and Toshikawa, J.
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Journal Title
The Astrophysical Journal
Volume: 821
Pages: 123
DOI
Peer Reviewed / Int'l Joint Research
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