T. Nishimichi - Academia.edu (original) (raw)

Papers by T. Nishimichi

The HSC collaboration team: S. Abe, H. Aihara, M. Akiyama, K. Aoki, N. Arimoto, N. A. Bahcall, S.... more The HSC collaboration team: S. Abe, H. Aihara, M. Akiyama, K. Aoki, N. Arimoto, N. A. Bahcall, S. J. Bickerton, J. Bosch, K. Bundy†(3), C. W. Chen, M. Chiba†(4), T. Chiba, N. E. Chisari, J. Coupon, M. Doi, M. Enoki S. Foucaud, M. Fukugita, H. Furusawa†(5), T. Futamase, R. Goto, T. Goto, J. E. Greene, J. E. Gunn†(6), T. Hamana†(5), T. Hashimoto, M. Hayashi, Y. Higuchi, C. Hikage, J. C. Hill, P. T. P. Ho, B. C. Hsieh, K. Y. Huang†(7), H. Ikeda, M. Imanishi, N. Inada, A. K. Inoue, W.-H. Ip, T. Ito, K. Iwasawa, M. Iye, H. Y. Jian, Y. Kakazu, H. Karoji, N. Kashikawa, N. Katayama, T. Kawaguchi, S. Kawanomoto, I. Kayo, T. Kitayama, G. R. Knapp, T. Kodama, K. Kohno, M. Koike, E. Kokubo, M. Kokubo, Y. Komiyama, A. Konno, Y. Koyama, C. N. Lackner, D. Lang, A. Leauthaud†(3), M. J. Lehner, K.Y. Lin, L. Lin, Y.-T. Lin†(7), C. P. Loomis, R. H. Lupton†(6), P. S. Lykawka, K. Maeda, R. Mandelbaum†(22), Y. Matsuda, K. Matsuoka, Y. Matsuoka, S. Mineo, T. Minezaki, H. Miyatake, R. Momose, A. More, S. M...

Monthly Notices of the Royal Astronomical Society

The response function of a linear system undergoing a non-linear transformation measures the sens... more The response function of a linear system undergoing a non-linear transformation measures the sensitivity of the non-linear output with respect to the initial linear state. This concept can also be applied to the non-linear growth of structures in the Universe. In this paper, we study the response function for the Halofit model, we present its analytic structure and we compare its theoretical prediction with the one as measured from simulations. We find a major departure between the two. We argue that a consequence of unmatched response functions is an intrinsic theoretical limitation on Halofit to predict the derivatives of the non-linear power spectrum with respect to cosmological parameters, and hence a possible systematic effect on Fisher matrices based forecasts using Halofit. In particular, we use a simple cosmological model with two parameters (As, ns) to illustrate the impact of using Halofit for this kind of forecasts for a 1 h−3 Gpc3 volume survey. We report a maximum impac...

Monthly Notices of the Royal Astronomical Society

Non-Gaussianities of dynamical origin are disentangled from primordial ones using the formalism o... more Non-Gaussianities of dynamical origin are disentangled from primordial ones using the formalism of large deviation statistics with spherical collapse dynamics. This is achieved by relying on accurate analytical predictions for the one-point probability distribution function (PDF) and the two-point clustering of spherically-averaged cosmic densities (sphere bias). Sphere bias extends the idea of halo bias to intermediate density environments and voids as underdense regions. In the presence of primordial non-Gaussianity, sphere bias displays a strong scale dependence relevant for both high and low density regions, which is predicted analytically. The statistics of densities in spheres are built to model primordial non-Gaussianity via an initial skewness with a scale-dependence that depends on the bispectrum of the underlying model. The analytical formulas with the measured nonlinear dark matter variance as input are successfully tested against numerical simulations. For local non-Gaussianity with a range from f NL = −100 to +100 they are found to agree within 2% or better for densities ρ ∈ [0.5, 3] in spheres of radius 15 Mpc/h down to z = 0.35. The validity of the large deviation statistics formalism is thereby established for all observationally relevant local-type departures from perfectly Gaussian initial conditions. The corresponding estimators for the amplitude of the nonlinear variance σ 8 and primordial skewness f NL are validated using a fiducial joint maximum likelihood experiment. The influence of observational effects and the prospects for a future detection of primordial non-Gaussianity from joint one-and two-point densities-in-spheres statistics are discussed.

Physical Review D

Using N-body simulations of cosmological large-scale structure formation, for the first time, we ... more Using N-body simulations of cosmological large-scale structure formation, for the first time, we show that the anisotropic primordial non-Gaussianity causes a scale-dependent modification, given by 1=k 2 at small k limit, in the three-dimensional power spectra of halo shapes (intrinsic alignments), whilst the conventional power spectrum of halo number density field remains unaffected. We discuss that wide-area imaging and spectrocopic surveys observing the same region of the sky allow us to constrain the quadrupole primordial non-Gaussianity coefficient f s¼2 NL at a precision comparable with or better than that of the cosmic microwave background.

Monthly Notices of the Royal Astronomical Society

To understand the nature of the accelerated expansion of the Universe, we need to combine constra... more To understand the nature of the accelerated expansion of the Universe, we need to combine constraints on the expansion rate and growth of structure. The growth rate is usually extracted from 3D galaxy maps by exploiting the effects of peculiar motions on galaxy clustering. However, theoretical models of the probability distribution function (PDF) of galaxy pairwise peculiar velocities are not accurate enough on small scales to reduce the error on theoretical predictions to the level required to match the precision expected for measurements from future surveys. Here, we improve the modelling of the pairwise velocity distribution by using the Skew-T PDF, which has non-zero skewness and kurtosis. Our model accurately reproduces the redshift space multipoles (monopole, quadrupole, and hexadecapole) predicted by N-body simulations, above scales of about 10,h−1rmMpc10\, h^{-1}{\rm Mpc}10,h−1rmMpc. We illustrate how a Taylor expansion of the streaming model can reveal the contributions of the different moment...

Monthly Notices of the Royal Astronomical Society

We study shapes and alignments of 45 dark matter (DM) haloes and their brightest cluster galaxies... more We study shapes and alignments of 45 dark matter (DM) haloes and their brightest cluster galaxies (BCGs) using a sample of 39 massive clusters from Hubble Frontier Field (HFF), Cluster Lensing And Supernova survey with Hubble (CLASH), and Reionization Lensing Cluster Survey (RELICS). We measure shapes of the DM haloes by strong gravitational lensing, whereas BCG shapes are derived from their light profiles in Hubble Space Telescope images. Our measurements from a large sample of massive clusters presented here provide new constraints on DM and cluster astrophysics. We find that DM haloes are on average highly elongated with the mean ellipticity of 0.482 ± 0.028, and position angles of major axes of DM haloes and their BCGs tend to be aligned well with the mean value of alignment angles of 22.2 ± 3.9 deg. We find that DM haloes in our sample are on average more elongated than their BCGs with the mean difference of their ellipticities of 0.11 ± 0.03. In contrast, the Horizon-AGN cosmo...

Monthly Notices of the Royal Astronomical Society

There is a growing interest of using the intrinsic alignment (IA) of galaxy images as a tool to e... more There is a growing interest of using the intrinsic alignment (IA) of galaxy images as a tool to extract cosmological information complimentary to galaxy clustering analysis. Recently, Okumura & Taruya derived useful formulas for the intrinsic ellipticity–ellipticity correlation, the gravitational shear–intrinsic ellipticity correlation, and the velocity–intrinsic ellipticity correlation functions based on the linear alignment (LA) model. In this paper, using large-volume N-body simulations, we measure these alignment statistics for dark-matter haloes in real and redshift space and compare them to the LA and non-linear alignment model predictions. We find that anisotropic features of baryon acoustic oscillations in the IA statistics can be accurately predicted by our models. The anisotropy due to redshift-space distortions (RSDs) is also well described in the large-scale limit. Our results indicate that one can extract the cosmological information encoded in the IA through the Alcock...

Monthly Notices of the Royal Astronomical Society

Using the motion of accreting particles on to haloes in cosmological N-body simulations, we study... more Using the motion of accreting particles on to haloes in cosmological N-body simulations, we study the radial phase-space structures of cold dark matter (CDM) haloes. In CDM cosmology, formation of virialized haloes generically produces radial caustics, followed by multistream flows of accreted dark matter inside the haloes. In particular, the radius of the outermost caustic called the splashback radius exhibits a sharp drop in the slope of the density profile. Here, we focus on the multistream structure of CDM haloes inside the splashback radius. To analyse this, we use and extend the SPARTA algorithm developed by Diemer. By tracking the particle trajectories accreting on to the haloes, we count their number of apocentre passages, which is then used to reveal the multistream flows of the dark matter particles. The resultant multistream structure in radial phase space is compared with the prediction of the self-similar solution by Fillmore & Goldreich for each halo. We find that $\si...

Physical Review D

Clustering properties and peculiar velocities of halos in large-scale structure carry a wealth of... more Clustering properties and peculiar velocities of halos in large-scale structure carry a wealth of cosmological information over a wide range of scales from linear to nonlinear scales. We use halo catalogs in a suite of highresolution N-body simulations to construct mock catalogs of galaxies that resemble the SDSS-like luminous early-type galaxies at three redshift bins in the range 0.15 ≤ z ≤ 0.7. To do this we include 10 nuisance parameters to model variations in halo-galaxy connections for each redshift bin; the halo occupation distribution, and the spatial and velocity distributions of galaxies in the host halos. We evaluate the Fisher information matrix for the redshift-space power spectrum of SDSS-like galaxies using different sets of the mock catalogs that are generated from changes in each of model parameters; cosmological parameters (σ 8 and Ω m ), the halo-galaxy connection parameters, and the cosmological distances (D A and H parameters at each redshift bin) for modeling an apparent geometrical distortion of the redshift-space power spectrum (the Alcock-Paczynski effect). We show that combining the monopole and quadrupole power spectra of galaxies allows for precise estimations of the cosmological parameters and the cosmological distances, even after marginalization over the halo-galaxy parameters, by lifting the parameter degeneracies that are otherwise inevitable if either of the two spectra alone is used. When including the galaxy power spectrum information up to k = 0.3 h Mpc −1 , we find about factor of 6 gain in the cosmological information content of (σ 8 , Ω m , D A 's and H's) compared to k = 0.2 h Mpc −1 . We also discuss the use of redshift-space galaxy power spectrum for a model-independent measurement of redshift-space distortion strength and a possible impact of the assembly bias on the cosmological parameters.

Journal of Cosmology and Astroparticle Physics

We study a new procedure to measure the sound horizon scale via Baryonic Acoustic Oscillations (B... more We study a new procedure to measure the sound horizon scale via Baryonic Acoustic Oscillations (BAO). Instead of fitting the measured power spectrum (PS) to a theoretical model containing the cosmological informations and all the nonlinear effects, we define a procedure to project out (or to "extract") the oscillating component from a given nonlinear PS. We show that the BAO scale extracted in this way is extremely robust and, moreover, can be reproduced by simple theoretical models at any redshift. By using N-body simulations, we discuss the effect of the nonlinear evolution of the matter field, of redshift space distortions and of scale-dependent halo bias, showing that all these effects can be reproduced with sub-percent accuracy. We give a one-parameter theoretical model based on a simple (IR) modification of 1loop perturbation theory, which reproduces the BAO scale from measurements of halo clustering in redshift space at better than 0.1% level and does not need any external UV input, such as coefficients measured from N-body simulations.

Physical Review D

We present numerical measurements of the power spectrum response function of the gravitational gr... more We present numerical measurements of the power spectrum response function of the gravitational growth of cosmic structures, defined as the functional derivative of the nonlinear spectrum with respect to the linear counterpart, based on 1, 400 cosmological simulations. We develop a simple analytical model based on a regularization of the standard perturbative calculation. Using the model prediction, we show that this function gives a natural way to interpolate the nonlinear power spectrum over cosmological parameter space from single or multi-step interpolations. We demonstrate that once an accurate numerical spectrum template is available for one (or a small number of) cosmological model(s), it doubles the range in k for which percent level accuracy can be obtained even for large change in the cosmological parameters. The python package RESPRESSO we developed to make those predictions is publicly available.

The Astrophysical Journal

Calabrese, Erminia 2019. Weak-lensing mass calibration of actpol sunyaev-zel'dovich clusters with... more Calabrese, Erminia 2019. Weak-lensing mass calibration of actpol sunyaev-zel'dovich clusters with the Hyper suprime-cam survey.

Physical Review D

We study the accuracy with which cosmological parameters can be determined from real space power ... more We study the accuracy with which cosmological parameters can be determined from real space power spectrum of matter density contrast at weakly nonlinear scales using analytical approaches. From power spectra measured in N -body simulations and using Markov chain Monte-Carlo technique, the best-fitting cosmological input parameters are determined with several analytical methods as a theoretical template, such as the standard perturbation theory, the regularized perturbation theory, and the effective field theory. We show that at redshift 1, all two-loop level calculations can fit the measured power spectrum down to scales k ∼ 0.2 h Mpc −1 and cosmological parameters are successfully estimated in an unbiased way. Introducing the Figure of bias (FoB) and Figure of merit (FoM) parameter, we determine the validity range of those models and then evaluate their relative performances. With one free parameter, namely the damping scale, the regularized perturbation theory is found to be able to provide the largest FoM parameter while keeping the FoB in the acceptance range. PACS numbers: 98.80.-k, 98.80.Es

The Astrophysical Journal

We present 108 full-sky gravitational lensing simulation data sets generated by performing multip... more 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 h 150 Mpc 1 comoving radial distance (corresponding to a redshift interval of z 0.05 D  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 ℓ 3000 = (or at an angular scale 0.5 q > arcmin). The simulation data sets are generated primarily for the ongoing Subaru Hyper Suprime-Cam survey, but are freely available for download at http://cosmo.phys.hirosaki-u.ac.jp/ takahasi/allsky_raytracing/.

Physics Letters B

In order to infer the impact of the small-scale physics to the large-scale properties of the univ... more In order to infer the impact of the small-scale physics to the large-scale properties of the universe, we use a series of cosmological N -body simulations of selfgravitating matter inhomogeneities to measure, for the first time, the response function of such a system defined as a functional derivative of the nonlinear power spectrum with respect to its linear counterpart. Its measured shape and amplitude are found to be in good agreement with perturbation theory predictions except for the coupling from small to large-scale perturbations. The latter is found to be significantly damped, following a Lorentzian form. These results shed light on validity regime of perturbation theory calculations giving a useful guideline for regularization of small scale effects in analytical modeling. Most importantly our result indicates that the statistical properties of the large-scale structure of the universe are remarkably insensitive to the details of the small-scale physics, astrophysical or gravitational, paving the way for the derivation of robust estimates of theoretical uncertainties on the determination of cosmological parameters from large-scale survey observations.

Physical Review D

We investigate the splashback features of dark-matter halos based on cosmic density and velocity ... more We investigate the splashback features of dark-matter halos based on cosmic density and velocity fields. Besides the density correlation function binned by the halo orientation angle which was used in the literature, we introduce, for the first time, the corresponding velocity statistic, alignment momentum correlation function, to take into account the asphericity of halos. Using large-volume, high-resolution N -body simulations, we measure the alignment statistics of density and velocity. On halo scales, x ∼ R200m ∼ 1 h −1 Mpc, we detect a sharp steepening in the momentum correlation associated with the physical halo boundary, or the splashback feature, which is found more prominent than in the density correlation. We also find that the splashback radius determined from the density correlation becomes ∼ 3.5% smaller than that from the momentum correlation, with their correlation coefficient being 0.605. Moreover, the orientation-dependent splashback feature due to halo asphericity is measured when the density profile is determined by dark-matter particles, which can be used as a test of collisional CDM since the halo shape is predicted to be rounder in such a model. PACS numbers: 98.80.-k

Monthly Notices of the Royal Astronomical Society

We study the dependence of surface mass density profiles, which can be directly measured by weak ... more We study the dependence of surface mass density profiles, which can be directly measured by weak gravitational lensing, on the orientation of haloes with respect to the line-of-sight direction, using a suite of N-body simulations. We find that, when major axes of haloes are aligned with the line-of-sight direction, surface mass density profiles have higher amplitudes than those averaged over all halo orientations, over all scales from 0.1 to 100 Mpc/h we studied. While the orientation dependence at small scales is ascribed to the halo triaxiality, our results indicate even stronger orientation dependence in the so-called two-halo regime, up to 100 Mpc/h. The orientation dependence for the two-halo term is well approximated by a multiplicative shift of the amplitude and therefore a shift in the halo bias parameter value. The halo bias from the two-halo term can be overestimated or underestimated by up to ∼ 30% depending on the viewing angle, which translates into the bias in estimated halo masses by up to a factor of two from halo bias measurements. The orientation dependence at large scales originates from the anisotropic halo-matter correlation function, which has an elliptical shape with the axis ratio of ∼ 0.55 up to 100 Mpc/h. We discuss potential impacts of halo orientation bias on other observables such as optically selected cluster samples and a clustering analysis of large-scale structure tracers such as quasars.

Monthly Notices of the Royal Astronomical Society

Physical Review D

Monthly Notices of the Royal Astronomical Society

Physical Review D

Journal of Cosmology and Astroparticle Physics

Physical Review D

The Astrophysical Journal

Physical Review D

The Astrophysical Journal

Physics Letters B

Physical Review D

Monthly Notices of the Royal Astronomical Society