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大里 健

オオサト ケン  (Ken Osato)

基本情報

所属
千葉大学 先進科学センター 助教
(兼任)大学院理学研究院 物理学研究部門 助教
学位
博士（理学）(2019年3月 東京大学)
修士（理学）(2016年3月 東京大学)
研究者番号
00914277
ORCID ID
 https://orcid.org/0000-0002-7934-2569
J-GLOBAL ID
202101012137702608
researchmap会員ID
R000025251

研究キーワード

 2

主要な研究分野

 2
もっとみる

経歴

 5

学歴

 2

受賞

 1

論文

 57
  • Murata, Ryoma, Nishimichi, Takahiro, Takada, Masahiro, Miyatake, Hironao, Shirasaki, Masato, More, Surhud, Takahashi, Ryuichi, Osato, Ken
    The Astrophysical Journal 854(2) 2018年2月  
    We constrain the scaling relation between optical richness (λ) and halo mass (M) for a sample of Sloan Digital Sky Survey (SDSS) red-sequence Matched-filter Probabilistic Percolation (redMaPPer) galaxy clusters within the context of the Planck cosmological model. We use a forward modeling approach where we model the probability distribution of optical richness for a given mass, P({ln}λ | M). To model the abundance and the stacked lensing profiles, we use an emulator specifically built to interpolate the halo mass function and the stacked lensing profile for an arbitrary set of halo mass and redshift, which is calibrated based on a suite of high-resolution N-body simulations. We apply our method to 8312 SDSS redMaPPer clusters with 20 ≤ λ ≤ 100 and 0.10 ≤ z λ ≤ 0.33 and show that the lognormal distribution model for P(λ | M), with four free parameters, well reproduces the measured abundances and lensing profiles simultaneously. The constraints are characterized by the mean relation, < {ln}λ > (M)=A+B{ln}(M/{M}pivot}), with A={3.207}-0.046+0.044 and B={0.993}-0.055+0.041 (68% CL), where the pivot mass scale M pivot = 3 × 1014 h -1 M ⊙, and the scatter {σ }lnλ | M}={σ }0+q{ln}(M/{M}pivot}) with {σ }0={0.456}-0.039+0.047 and q=-{0.169}-0.026+0.035. We find that a large scatter in halo masses is required at the lowest-richness bins (20 ≤ λ ≲ 30) in order to reproduce the measurements. Without such a large scatter, the model prediction for the lensing profiles tends to overestimate the measured amplitudes. This might imply a possible contamination of intrinsically low-richness clusters due to the projection effects. Such a low-mass halo contribution is significantly reduced when applying our method to the sample of 30 ≤ λ ≤ 100....
  • Aihara, Hiroaki, Arimoto, Nobuo, Armstrong, Robert, Arnouts, Stéphane, Bahcall, Neta A., Bickerton, Steven, Bosch, James, Bundy, Kevin, Capak, Peter L., Chan, James H. H., Chiba, Masashi, Coupon, Jean, Egami, Eiichi, Enoki, Motohiro, Finet, Francois, Fujimori, Hiroki, Fujimoto, Seiji, Furusawa, Hisanori, Furusawa, Junko, Goto, Tomotsugu, Goulding, Andy, Greco, Johnny P., Greene, Jenny E., Gunn, James E., Hamana, Takashi, Harikane, Yuichi, Hashimoto, Yasuhiro, Hattori, Takashi, Hayashi, Masao, Hayashi, Yusuke, Hełminiak, Krzysztof G., Higuchi, Ryo, Hikage, Chiaki, Ho, Paul T. P., Hsieh, Bau-Ching, Huang, Kuiyun, Huang, Song, Ikeda, Hiroyuki, Imanishi, Masatoshi, Inoue, Akio K., Iwasawa, Kazushi, Iwata, Ikuru, Jaelani, Anton T., Jian, Hung-Yu, Kamata, Yukiko, Karoji, Hiroshi, Kashikawa, Nobunari, Katayama, Nobuhiko, Kawanomoto, Satoshi, Kayo, Issha, Koda, Jin, Koike, Michitaro, Kojima, Takashi, Komiyama, Yutaka, Konno, Akira, Koshida, Shintaro, Koyama, Yusei, Kusakabe, Haruka, Leauthaud, Alexie, Lee, Chien-Hsiu, Lin, Lihwai, Lin, Yen-Ting, Lupton, Robert H., Mandelbaum, Rachel, Matsuoka, Yoshiki, Medezinski, Elinor, Mineo, Sogo, Miyama, Shoken, Miyatake, Hironao, Miyazaki, Satoshi, Momose, Rieko, More, Anupreeta, More, Surhud, Moritani, Yuki, Moriya, Takashi J., Morokuma, Tomoki, Mukae, Shiro, Murata, Ryoma, Murayama, Hitoshi, Nagao, Tohru, Nakata, Fumiaki, Niida, Mana, Niikura, Hiroko, Nishizawa, Atsushi J., Obuchi, Yoshiyuki, Oguri, Masamune, Oishi, Yukie, Okabe, Nobuhiro, Okamoto, Sakurako, Okura, Yuki, Ono, Yoshiaki, Onodera, Masato, Onoue, Masafusa, Osato, Ken, Ouchi, Masami, Price, Paul A., Pyo, Tae-Soo, Sako, Masao, Sawicki, Marcin, Shibuya, Takatoshi, Shimasaku, Kazuhiro, Shimono, Atsushi, Shirasaki, Masato, Silverman, John D., Simet, Melanie, Speagle, Joshua, Spergel, David N., Strauss, Michael A., Sugahara, Yuma, Sugiyama, Naoshi, Suto, Yasushi, Suyu, Sherry H., Suzuki, Nao, Tait, Philip J., Takada, Masahiro, Takata, Tadafumi, Tamura, Naoyuki, Tanaka, Manobu M., Tanaka, Masaomi, Tanaka, Masayuki, Tanaka, Yoko, Terai, Tsuyoshi, Terashima, Yuichi, Toba, Yoshiki, Tominaga, Nozomu, Toshikawa, Jun, Turner, Edwin L., Uchida, Tomohisa, Uchiyama, Hisakazu, Umetsu, Keiichi, Uraguchi, Fumihiro, Urata, Yuji, Usuda, Tomonori, Utsumi, Yousuke, Wang, Shiang-Yu, Wang, Wei-Hao, Wong, Kenneth C., Yabe, Kiyoto, Yamada, Yoshihiko, Yamanoi, Hitomi, Yasuda, Naoki, Yeh, Sherry, Yonehara, Atsunori, Yuma, Suraphong
    Publications of the Astronomical Society of Japan 70(SP1) 2018年1月  
    Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2-m Subaru telescope on the summit of Mauna Kea in Hawaii. A team of scientists from Japan, Taiwan, and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg2 in five broad bands (grizy), with a 5 σ point-source depth of r ≈ 26. The Deep layer covers a total of 26 deg2 in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg2). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey....
  • Takahashi, Ryuichi, Hamana, Takashi, Shirasaki, Masato, Namikawa, Toshiya, Nishimichi, Takahiro, Osato, Ken, Shiroyama, Kosei
    The Astrophysical Journal 850(1) 24-24 2017年11月  
    We present 108 full-sky gravitational lensing simulation data sets generated by performing multiple-lens plane ray-tracing through high-resolution cosmological N-body simulations. The data sets include full-sky convergence and shear maps from redshifts z = 0.05 to 5.3 at intervals of 150 {h}-1{Mpc} comoving radial distance (corresponding to a redshift interval of { { Δ } }z≃ 0.05 at the nearby universe), enabling the construction of a mock shear catalog for an arbitrary source distribution up to z = 5.3. The dark matter halos are identified from the same N-body simulations with enough mass resolution to resolve the host halos of the Sloan Digital Sky Survey (SDSS) CMASS and luminous red galaxies (LRGs). Angular positions and redshifts of the halos are provided by a ray-tracing calculation, enabling the creation of a mock halo catalog to be used for galaxy-galaxy and cluster-galaxy lensing. The simulation also yields maps of gravitational lensing deflections for a source redshift at the last scattering surface, and we provide 108 realizations of lensed cosmic microwave background (CMB) maps in which the post-Born corrections caused by multiple light scattering are included. We present basic statistics of the simulation data, including the angular power spectra of cosmic shear, CMB temperature and polarization anisotropies, galaxy-galaxy lensing signals for halos, and their covariances. The angular power spectra of the cosmic shear and CMB anisotropies agree with theoretical predictions within 5% up to {\ell }=3000 (or at an angular scale θ &gt; 0.5 arcmin). The simulation data sets are generated primarily for the ongoing Subaru Hyper Suprime-Cam survey, but are freely available for download at <A href="http://cosmo.phys.hirosaki-u.ac.jp/takahasi/allsky_raytracing/">http://cosmo.phys.hirosaki-u.ac.jp/takahasi/allsky_raytracing/</A>....
  • Teppei Okumura, Takahiro Nishimichi, Keiichi Umetsu, Ken Osato
    Phys. Rev. D 98, 023523 (2018) 98(2) 2017年6月27日  査読有り
    We investigate the effects of intrinsic alignments (IA) of dark-matter halo<br /> shapes on cosmic density and velocity fields from cluster to cosmic scales<br /> beyond 100 Mpc/h. Besides the density correlation function binned by the halo<br /> orientation angle which was used in the literature, we introduce, for the first<br /> time, the corresponding two velocity statistics, the angle-binned pairwise<br /> infall momentum and momentum correlation function. Using large-volume,<br /> high-resolution N-body simulations, we measure the alignment statistics of<br /> density and velocity, both in real and redshift space. We find that the<br /> alignment signal is not amplified by redshift-space distortions at linear<br /> scales. Behaviors of IA in the velocity statistics are similar to those in the<br /> density statistics, except that the halo orientations are aligned with the<br /> velocity field up to a scale larger than those with the density field, x&gt;100<br /> Mpc/h. On halo scales, x~ R_{200m} ~ 1 Mpc/h, we detect a sharp steepening in<br /> the momentum correlation associated with the physical halo boundary, or the<br /> splashback feature, which is found more prominent than in the density<br /> correlation. Our results indicate that observations of IA with the velocity<br /> field can provide additional information on cosmological models from large<br /> scales and on physical sizes of halos from small scales.
  • Osato, Ken, Sekiguchi, Toyokazu, Shirasaki, Masato, Kamada, Ayuki, Yoshida, Naoki
    Journal of Cosmology and Astroparticle Physics 2016年6月  
    Light gravitinos of mass lesssim O (10) eV are of particular interest in cosmology, offering various baryogenesis scenarios without suffering from the cosmological gravitino problem. The gravitino may contribute considerably to the total matter content of the Universe and affect structure formation from early to present epochs. After the gravitinos decouple from other particles in the early Universe, they free-stream and consequently suppress density fluctuations of (sub-)galactic length scales. Observations of structure at the relevant length-scales can be used to infer or constrain the mass and the abundance of light gravitinos. We derive constraints on the light gravitino mass using the data of cosmic microwave background (CMB) lensing from Planck and of cosmic shear from the Canada France Hawaii Lensing Survey survey, combined with analyses of the primary CMB anisotropies and the signature of baryon acoustic oscillations in galaxy distributions. The obtained constraint on the gravitino mass is m3/2 &lt; 4.7 eV (95 % C.L.), which is substantially tighter than the previous constraint from clustering analysis of Ly-α forests....
  • Suto, Daichi, Kitayama, Tetsu, Osato, Ken, Sasaki, Shin, Suto, Yasushi
    Publications of the Astronomical Society of Japan 2016年2月  
    The top-hat spherical collapse model (TSC) is one of the most fundamental analytical frameworks to describe the non-linear growth of cosmic structure. TSC has motivated, and been widely applied in, various investigations even in the current era of precision cosmology. While numerous studies exist to examine its validity against numerical simulations in a statistical fashion, there are few analyses which compare the TSC dynamics in an individual object-wise basis, which is what we attempt in the present paper. We extract 100 halos at z = 0 from a cosmological N-body simulation according to the conventional TSC criterion for the spherical over-density. Then we trace back their spherical counterparts at earlier epochs. Just prior to the turn-around epoch of the halos, their dynamics are well approximated by TSC, but their turn-around epochs are systematically delayed and the virial radii are larger by ∼20% on average relative to the TSC predictions. We find that this systematic deviation can mainly be ascribed to the non-uniformity/inhomogeneity of dark matter density profiles and the non-zero velocity dispersions, both of which are neglected in TSC. In particular, the inside-out collapse and shell-crossing of dark matter halos play an important role in generating the significant velocity dispersion. The implications of the present result are briefly discussed....
  • Osato, Ken, Shirasaki, Masato, Yoshida, Naoki
    The Astrophysical Journal 2015年6月  
    We study the impact of baryonic physics on cosmological parameter estimation with weak-lensing surveys. We run a set of cosmological hydrodynamics simulations with different galaxy formation models. We then perform ray-tracing simulations through the total matter density field to generate 100 independent convergence maps with a field of view of 25 { { deg }2}, and we use them to examine the ability of the following three lensing statistics as cosmological probes: power spectrum (PS), peak counts, and Minkowski functionals (MFs). For the upcoming wide-field observations, such as the Subaru Hyper Suprime-Cam (HSC) survey with a sky coverage of 1400 { { deg }2}, these three statistics provide tight constraints on the matter density, density fluctuation amplitude, and dark energy equation of state, but parameter bias is induced by baryonic processes such as gas cooling and stellar feedback. When we use PS, peak counts, and MFs, the magnitude of relative bias in the dark energy equation of state parameter w is at a level of, respectively, δ w∼ 0.017, 0.061, and 0.0011. For the HSC survey, these values are smaller than the statistical errors estimated from Fisher analysis. The bias could be significant when the statistical errors become small in future observations with a much larger survey area. We find that the bias is induced in different directions in the parameter space depending on the statistics employed. While the two-point statistic, i.e., PS, yields robust results against baryonic effects, the overall constraining power is weak compared with peak counts and MFs. On the other hand, using one of peak counts or MFs, or combined analysis with multiple statistics, results in a biased parameter estimate. The bias can be as large as 1σ for the HSC survey and will be more significant for upcoming wider-area surveys. We suggest to use an optimized combination so that the baryonic effects on parameter estimation are mitigated. Such a “calibrated” combination can place stringent and robust constraints on cosmological parameters....

書籍等出版物

 2

講演・口頭発表等

 49
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担当経験のある科目(授業)

 9
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所属学協会

 6
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共同研究・競争的資金等の研究課題

 6
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