Faculty Profiles - SUGIYAMA, Naoshi

Papers - SUGIYAMA, Naoshi

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Cosmological signatures of tilted isocurvature perturbations: reionization and 21cm fluctuations Reviewed Open Access

T. Sekiguchi, H. Tashiro, J. Silk, N. Sugiyama

Journal of Cosmology and Astroparticle Physics ( 03 ) page： 001 2014.3

The effect of primordial black holes on 21-cm fluctuations Reviewed Open Access

Hiroyuki Tashiro, Naoshi Sugiyama

Monthly Notices of the Royal Astronomical Society Vol. 435 ( 4 ) page： 3001-3008 2013.11

Optimal constraint on gNL from CMB Invited Reviewed Open Access

Toyokazu Sekiguchi, Naoshi Sugiyama

Journal of Cosmology and Astroparticle Physics Vol. 09 page： 002 2013.9

Understanding the nature of luminous red galaxies (LRGs): connecting LRGs to central and satellite subhaloes Reviewed Open Access

Shogo Masaki, Chiaki Hikage, Masahiro Takada, David Spergel, Naoshi Sugiyama

Monthly Notices of the Royal Astronomical Society Vol. 43 ( 4 ) page： 3506-3522 2013.8

Generation of magnetic fields in Einstein-aether gravity Reviewed Open Access

Shohei Saga, Maresuke Shiraichi, Kiyotomo Ichiki, Naoshi Sugiyama

Physical Review D Vol. 87 ( 10 ) page： 104025 2013.5

Exploring the origin of the fine structures in the CMB temperature angular power spectrum Reviewed Open Access

Kohei Kumazaki, Kiyotomo Ichiki, Naoshi Sugiyama, Joseph Silk

Physical Review D Vol. 87 ( 2 ) page： 023008 2013.1

Shadows of multi-black holes: Analytic exploration Reviewed

Akifumi Yumoto, Daisuke Nitta, Takeshi Chiba, Naoshi Sugiyama

Physical Review D Vol. 86 ( 10 ) page： 103001 2012.11

Stochastic gravitational wave background originating from halo mergers Reviewed Open Access

Takahiro Inagaki, Keitaro Takahashi, Naoshi Sugiyama

Physical Review D Vol. 85 ( 10 ) page： 104051 2012.5

Ionized bubble number count as a probe of non-Gaussianity Reviewed Open Access

Hiroyuki Tashiro, Naoshi Sugiyama

Monthly Notices of the Royal Astronomical Society, Vol. 420 ( 1 ) page： 441-446 2012.2

Constraint on the primordial vector mode and its magnetic field generation from seven-year Wilkinson Microwave Anisotropy Probe observations Reviewed Open Access

Kiyotomo Ichik, Keitaro Takahashi, Naoshi Sugiyama

Physical Review D Vol. 85 ( 4 ) page： 043009 2012.2

Fine features in the primordial power spectrum Reviewed Open Access

Kohei Kumazak, Shuichiro Yokoyama, Naoshi Sugiyama

Journal of Cosmology and Astroparticle Physics Vol. 12 page： 008 2011.12

Modification of the halo mass function by kurtosis associated with primordial non-Gaussianity Reviewed Open Access

Shuichiro Yokoyama, Naoshi Sugiyama, Saleem Zaroubi, Joseph Silk

Monthly Notices of the Royal Astronomical Society Vol. 417 ( 2 ) page： 1074-1087 2011.10

Language：English Publishing type：Research paper (scientific journal)

We study the halo mass function in the presence of a kurtosis type of primordial non-Gaussianity. The kurtosis corresponds to the trispectrum as defined in Fourier space. The primordial trispectrum is commonly characterized by two parameters, tau_NL and g_NL. We focus on tau_NL which is an important parameter to test the physics of multifield inflation models.

DOI： 10.1111/j.1365-2966.2011.19323.x

Shadows of colliding black holes Reviewed Open Access

Daisuke Nitta, Takeshi Chiba, Naoshi Sugiyama

Physical Review D Vol. 84 ( 6 ) 2011.9

Language：English Publishing type：Research paper (scientific journal)

We compute the shadows of colliding black holes using the Kastor-Traschen cosmological multiblack hole solution that is an exact solution describing the collision of maximally charged black holes with a positive cosmological constant. We find that in addition to the shadow of each black hole, an eyebrowlike structure appears as the black holes come close to each other. These features can be used as probes to find the multiblack hole system at the final stage of its merger process.

DOI： 10.1103/PhysRevD.84.063008

Formulation and constraints on decaying dark matter with finite mass daughter particles Reviewed Open Access

Shohei Aoyama, Kiyotomo Ichiki, Daisuke Nitta, Naoshi Sugiyama

Journal of Cosmology and Astroparticle Physics Vol. 2011 ( 09 ) page： 025 2011.9

Modification of the halo mass function by kurtosis associated with primordial non-Gaussianity Reviewed Open Access

Shuichiro Yokoyama, Naoshi Sugiyama, Saleem Zaroubi, Joseph Silk

Monthly Notices of the Royal Astronomical Society Vol. 417 ( 2 ) page： 1074-1087 2011.8

Observational Search for PeV-EeV Tau Neutrino from GRB081203A Reviewed Open Access

Y. Aita, Y. Asaoka, T. chonan, M. Jobashi, M. Masuda, Y. Morino, K. Noda, M. Sasaki, J. Asoh, N. Ishikawa, S. Ogawa, J.G. Lenearned, S. Matsuno, S. Olsen, P-M. Binder, J. Hamilton, N. Sugiyama, Y. Watanabe

The Astrophysical Journal Letters Vol. 736 ( 1 ) page： L12-L16 2011.7

Language：English Publishing type：Research paper (scientific journal)

We report the first observational search for tau neutrinos (ντ) from gamma-ray bursts (GRBs) using one of the Ashra light collectors. The Earth-skimming ντ technique of imaging Cherenkov τ showers was applied as a detection method. We set stringent upper limits on the ντ fluence in PeV-EeV region for 3780 s (between 2.83 and 1.78 hr before) and another 3780 s (between 21.2 and 22.2 hr after) surrounding GRB081203A triggered by the Swift satellite. This first search for PeV-EeV ντ complements other experiments in energy range and methodology, and suggests the prologue of "multi-particle astronomy" with a precise determination of time and location.

DOI： 10.1088/2041-8205/736/1/L12

Open Access

Sunyaev-Zel'dovich power spectrum produced by primordial magnetic fields Reviewed Open Access

Hiroyuki Tashiro, Naoshi Sugiyama

Monthly Notices of the Royal Astronomical Society Vol. 411 ( 2 ) page： 1284-1292 2011.2

Prospects for direct detection of inflationary gravitational waves by next generation interferometric detectors Reviewed Open Access

Sachiko Kuroyanagi, Takeshi Chiba, Naoshi Sugiyama

Physical Review D Vol. 83 ( 4 ) 2011.2

Language：English Publishing type：Research paper (scientific journal)

We study the potential impact of detecting the inflationary gravitational wave background by the future space-based gravitational wave detectors, such as DECIGO and BBO. The signal-to-noise ratio of each experiment is calculated for chaotic/natural/hybrid inflation models by using the precise predictions of the gravitational wave spectrum based on numerical calculations. We investigate the dependence of each inflation model on the reheating temperature which influences the amplitude and shape of the spectrum, and find that the gravitational waves could be detected for chaotic/natural inflation models with high reheating temperature. From the detection of the gravitational waves, a lower bound on the reheating temperature could be obtained. The implications of this lower bound on the reheating temperature for particle physics are also discussed.

DOI： 10.1103/PhysRevD.83.043514

Non-Gaussian Error Contribution to Likelihood Analysis of the Matter Power Spectrum Reviewed Open Access

RYuichi Takahashi, Naoki Yoshida, MAsahiro Takada, Takahiko Matsubara, Naoshi Sugiyama, Issha Kayo, Takahiro Nishimichi, Shun Saito, Atsushi Taruya

Astrophysical Journal Vol. 726 ( 1 ) page： 7 2011.1

Language：English Publishing type：Research paper (scientific journal)

We study the sample variance of the matter power spectrum for the standard Λ cold dark matter universe. We use a total of 5000 cosmological N-body simulations to study in detail the distribution of best-fit cosmological parameters and the baryon acoustic peak positions. The obtained distribution is compared with the results from the Fisher matrix analysis with and without including non-Gaussian errors. For the Fisher matrix analysis, we compute the derivatives of the matter power spectrum with respect to cosmological parameters using directly full nonlinear simulations. We show that the non-Gaussian errors increase the unmarginalized errors by up to a factor of five for k max = 0.4 h Mpc–1 if there is only one free parameter, provided other parameters are well determined by external information. On the other hand, for multi-parameter fitting, the impact of the non-Gaussian errors is significantly mitigated due to severe parameter degeneracies in the power spectrum. The distribution of the acoustic peak positions is well described by a Gaussian distribution, with its width being consistent with the statistical interval predicted from the Fisher matrix. We also examine systematic bias in the best-fit parameter due to the non-Gaussian errors. The bias is found to be smaller than the 1σ statistical error for both the cosmological parameters and the acoustic scale positions.

DOI： 10.1088/0004-637X/726/1/7

Open Access

Halo occupation distribution of massive galaxies since z= 1 Reviewed Open Access

Y. Matsuoka, S. Masaki, K. Kawara, Naoshi Suigyama

Monthly Notices of the Royal Astronomical Society Vol. 410 ( 1 ) page： 548-558 2011.1

Language：English Publishing type：Research paper (scientific journal)

We present a clustering analysis of ˜60 000 massive (stellar mass M★ > 1011 Mȯ) galaxies out to z= 1 drawn from 55.2 deg2 of the UKIRT Infrared Deep Sky Survey (UKIDSS) and the Sloan Digital Sky Survey (SDSS) II Supernova Survey. Strong clustering is detected for all the subsamples of massive galaxies characterized by different stellar masses (M★= 1011.0-11.5 Mȯ, 1011.5-12.0 Mȯ) or rest-frame colours (blue: U-V < 1.0, red: U-V > 1.0). We find that more mature (more massive or redder) galaxies are more clustered, which implies that the more mature galaxies have started stellar-mass assembly earlier within the highly biased region where the structure formation has also started earlier. By means of halo occupation distribution (HOD) models fitted to the observed angular correlation function, we infer the properties of the underlying host dark haloes. We find that the estimated bias factors and host halo masses are systematically larger for galaxies with larger stellar masses, which is consistent with the general agreement that the capability of hosting massive galaxies depends strongly on halo mass. The estimated effective halo masses are ˜1014 Mȯ, which gives the stellar-mass to halo-mass ratios of ˜0.003. The observed evolution of bias factors indicates rapid evolution of spatial distributions of cold dark matter relative to those traced by the massive galaxies, while the transition of host halo masses might imply that the fractional mass growth rate of haloes is less than those of stellar systems. The inferred halo masses and high fractions of central galaxies indicate that the massive galaxies in the current sample are possibly equivalent to central galaxies of galaxy clusters.

DOI： 10.1111/j.1365-2966.2010.17464.x

Open Access

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Papers - SUGIYAMA, Naoshi