公募研究
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.
2: おおむね順調に進展している
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.
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.
すべて 2017 2016
すべて 雑誌論文 (7件) (うち国際共著 7件、 査読あり 7件) 学会発表 (2件) (うち国際学会 2件)
MNRAS
巻: 465 ページ: 4853-4865
10.1093/mnras/stw3056
巻: 465 ページ: 2411-2419
10.1093/mnras/stw2924
Astrophysical Journal Letters
巻: 835 ページ: L25
10.3847/2041-8213/835/2/L25
The Astrophysical Journal
巻: 825 ページ: 39
10.3847/0004-637X/825/1/39
Publications of the Astronomical Society of Japan
巻: 68 ページ: 38
10.1093/pasj/psw029
巻: 457 ページ: 3200-3218
10.1093/mnras/stw188
巻: 821 ページ: 123
10.3847/0004-637X/821/2/123