Sunao Sugiyama 교수

A new analysis of the distribution of matter in the Universe continues to find a discrepancy in the clumpiness of dark matter in the late and early Universe, suggesting a fundamental error in the standard cosmological model.

Primordial black holes (PBHs) can constitute the predominant fraction of dark matter (DM) if PBHs reside in the currently unconstrained “sublunar” mass range. PBHs originating from scalar perturbations generated during inflation can naturally appear with a broad spectrum in a class of models. The resulting stochastic gravitational wave (GW) background generated from such PBH production can account for the recently reported North American Nanohertz Observatory for Gravitational Waves (NANOGrav) p

ABSTRACT Microlensing of stars, e.g. in the Galactic bulge and Andromeda galaxy (M31), is among the most robust, powerful method to constrain primordial black holes (PBHs) that are a viable candidate of dark matter. If PBHs are in the mass range $M_{\rm PBH} {\,\,\lesssim \,\,}10^{-10}\mathrm{ M}_\odot$, its Schwarzschild radius (rSch) becomes comparable with or shorter than optical wavelength (λ) used in a microlensing search, and in this regime the wave optics effect on microlensing needs to b

We assess the performance of a perturbation theory inspired method for inferring cosmological parameters from the joint measurements of galaxy-galaxy weak lensing ($\mathrm{\ensuremath{\Delta}}\mathrm{\ensuremath{\Sigma}}$) and the projected galaxy clustering (${w}_{p}$). To do this, we use a wide variety of mock galaxy catalogs constructed based on a large set of $N$-body simulations that mimic the Subaru HSC-Y1 and SDSS galaxies and apply the method to the mock signals to address whether to re

Dark matter in the form of axions is expected to form axion stars. Such axion stars could be discovered by microlensing events. In particular, some candidate events reported by Subaru HSC and OGLE can be explained simultaneously if the axion stars with masses of the order of the Earth mass make up about ∼27−13+7 percent of dark matter. For QCD axions, this corresponds to the axion mass in the range 10−9−10−6 eV, which is consistent with the experimental constraints, as well as the cosmological a

We present cosmological parameter constraints from a blinded joint analysis of galaxy-galaxy weak lensing, $\mathrm{\ensuremath{\Delta}}\mathrm{\ensuremath{\Sigma}}(R)$, and the projected correlation function, ${w}_{\mathrm{p}}(R)$, measured from the first-year HSC (HSC-Y1) data and SDSS spectroscopic galaxies over $0.15<z<0.7$. We use luminosity-limited samples as lens samples for $\mathrm{\ensuremath{\Delta}}\mathrm{\ensuremath{\Sigma}}$ and as large-scale structure tracers for ${w}_{\ma

We present cosmological parameter constraints from a blind joint analysis of three two-point correlation functions measured from the Year 3 Hyper Suprime-Cam (HSC-Y3) imaging data, covering 416 deg$^2$, and the SDSS DR11 spectroscopic galaxies spanning the redshift range $[0.15, 0.70]$. We subdivide the SDSS galaxies into three volume-limited samples separated in redshift, each of which acts as a large-scale structure tracer characterized by the measurement of the projected correlation function,

Dark matter in the form of axions is expected to form miniclusters, and their dense regions can harbor compact axion stars. Such axion stars could be discovered by microlensing events. In particular, some candidate events reported by Subaru HSC and OGLE can be explained simultaneously if the axion stars with masses of the order of the Earth mass make up about $\sim27^{+7}_{013}$ percent of dark matter. For QCD axions, this corresponds to the axion mass in the range $10^{-9}-10^{-6}$ eV, which is

The three-point correlation function (3PCF) of a weak lensing shear field contains information that is complementary to that in the two-point correlation function (2PCF), which can help improve the cosmological parameters and calibrate astrophysical and observational systematics parameters. However, the application of the 3PCF to observed data has been limited due to the computational challenges of calculating theoretical predictions of the 3PCF from a bispectrum model. In this paper, we present

In many fields including cosmology, statistical inference often relies on Gaussian likelihoods whose covariance matrices are estimated from a finite number of simulations. This finite-sample estimation introduces noise into the covariance, which propagates to parameter estimates, a phenomenon known as the Dodelson-Schneider (DS) effect, leading to inflated uncertainties. While the Massively optimized parameter estimation and data compression (MOPED) algorithm offers lossless Fisher information-p

In many fields including cosmology, statistical inference often relies on Gaussian likelihoods whose covariance matrices are estimated from a finite number of simulations. This finite-sample estimation introduces noise into the covariance, which propagates to parameter estimates, a phenomenon known as the Dodelson-Schneider (DS) effect, leading to inflated uncertainties. While the Massively Optimized Parameter Estimation and Data compression (MOPED) algorithm offers lossless Fisher information-p

The extended source effect on microlensing magnification is non-negligible and must be taken into account for in an analysis of microlensing. However, the evaluation of the extended source magnification is numerically expensive because it includes the two-dimensional integral over source profile. Various studies have developed methods to reduce this integral down to the one-dimensional-integral or integral-free form, which adopt some approximations or depend on the exact form of the source profi

We present cosmological parameter constraints from a blinded joint analysis of galaxy-galaxy weak lensing, $Δ\!Σ(R)$, and projected correlation function, $w_\mathrm{p}(R)$, measured from the first-year HSC (HSC-Y1) data and SDSS spectroscopic galaxies over $0.150.75$ for the $Δ\!Σ$ measurements, selected based on their photometric redshifts. For theoretical template, we use the "minimal bias" model for the cosmological clustering observables for the flat $Λ$CDM cosmological model. We compare the

Abstract The extended source effect on microlensing magnification is nonnegligible and must be taken into account for an analysis of microlensing. However, the evaluation of the extended source magnification is numerically expensive because it includes the two-dimensional integral over the source profile. Various studies have developed methods to reduce this integral down to the one-dimensional-integral- or integral-free form, which adopt some approximations or depend on the exact form of the so

We present cosmological parameter constraints from a blinded joint analysis of galaxy-galaxy weak lensing, $\Delta\!\Sigma(R)$, and projected correlation function, $w_\mathrm{p}(R)$, measured from the first-year HSC (HSC-Y1) data and SDSS spectroscopic galaxies over $0.15<z<0.7$. We use luminosity-limited samples as lens samples for $\Delta\!\Sigma$ and as large-scale structure tracers for $w_\mathrm{p}$ in three redshift bins, and use the HSC-Y1 galaxy catalog to define a secure sample of sourc