104 citations · 1.1k across the 42 of their papers we have counts for
42 papers
Final results for mapping the Milky Way's stellar halo with blue horizontal-branch stars selected from the Subaru Hyper Supreme-Cam Survey
Tetsuya Fukushima, Masashi Chiba, Mikito Tanaka +7
We select blue-horizontal branch stars (BHBs) from the internal data release of the Hyper Suprime-Cam Subaru Strategic Program to reveal the global structure of the Milky Way (MW)…
Indirect Detection of Decaying Dark Matter with High Angular Resolution: Case for axion search by IRCS at Subaru Telescope
Wen Yin, Kohei Hayashi
Recent advances in cosmic-ray detectors have provided exceptional sensitivities of dark matter with high angular resolution. Motivated by this, we present a comprehensive study of…
EMPRESS. XII. Statistics on the Dynamics and Gas Mass Fraction of Extremely-Metal Poor Galaxies
Yi Xu, Masami Ouchi, Yuki Isobe +49
We present demography of the dynamics and gas-mass fraction of 33 extremely metal-poor galaxies (EMPGs) with metallicities of and low stellar masses of $10^4-…
Study of structural parameters and systemic proper motion of Sextans dwarf spheroidal galaxy with Subaru Hyper Suprime-Cam data
Akira Tokiwa, Masahiro Takada, Tian Qiu +4
We use the Subaru Hyper Suprime-Cam (HSC) data to study structural parameters and systemic proper motion of the Sextans dwarf spheroidal galaxy at the heliocentric distance of 86 k…
The Missing Satellite Problem Outside of the Local Group. II. Statistical Properties of Satellites of Milky Way-like Galaxies
Masashi Nashimoto, Masayuki Tanaka, Masashi Chiba +3
We present a new observation of satellite galaxies around seven Milky Way (MW)-like galaxies located outside of the Local Group (LG) using Subaru/Hyper Suprime-Cam imaging data to…
Cosmological prior for the -factor estimation of dwarf spheroidal galaxies
Shun'ichi Horigome, Kohei Hayashi, Shin'ichiro Ando
Dark matter halos of dwarf spheroidal galaxies (dSphs) play important roles in dark matter detection. Generally we estimate the halo profile using a kinematical equation of dSphs b…
Dark matter halo properties of the Galactic dwarf satellites: implication for chemo-dynamical evolution of the satellites and a challenge to CDM
Kohei Hayashi, Yutaka Hirai, Masashi Chiba +1
Elucidating dark matter density profiles in the Galactic dwarf satellites is essential to understanding not only the quintessence of dark matter, but also the evolution of the sate…
EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-Poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension
Akinori Matsumoto, Masami Ouchi, Kimihiko Nakajima +42
The primordial He abundance is a powerful probe of cosmology. Currently, is best determined by observations of metal-poor galaxies, while there are on…
The Diversity of Core Halo Structure in the Fuzzy Dark Matter Model
Hei Yin Jowett Chan, Elisa G. M. Ferreira, Simon May +2
In the fuzzy dark matter (FDM) model, gravitationally collapsed objects always consist of a solitonic core located within a virialised halo. Although various numerical simulations…
Constraining Self-Interacting Dark Matter with Dwarf Spheroidal Galaxies and High-resolution Cosmological -body Simulations
Toshihiro Ebisu, Tomoaki Ishiyama, Kohei Hayashi
We study the density structures of dark matter subhalos for both cold dark matter and self-interacting dark matter models using high-resolution cosmological -body simulations. W…
An Arecibo 327 MHz Search for Radio Pulsars and Bursts in the Dwarf Irregular Galaxies Leo A and T
Fronefield Crawford, Kohei Hayashi
We have conducted an Arecibo 327 MHz search of two dwarf irregular galaxies in the Local Group, Leo A and T, for radio pulsars and single pulses from fast radio bursts and other gi…
A one-phase Stefan problem with non-linear diffusion from highly competing two-species particle systems
Kohei Hayashi
We consider an interacting particle system with two species under strong competition dynamics between the two species. Then, through the hydrodynamic limit procedure for the micros…
Interstellar Gas Heating by Primordial Black Holes
Volodymyr Takhistov, Philip Lu, Graciela B. Gelmini +3
Interstellar gas heating is a powerful cosmology-independent observable for exploring the parameter space of primordial black holes (PBHs) formed in the early Universe that could c…
Narrowing the mass range of Fuzzy Dark Matter with Ultra-faint Dwarfs
Kohei Hayashi, Elisa G. M. Ferreira, Hei Yin Jowett Chan
Fuzzy dark matter (FDM) is an attractive dark matter candidate motivated by small scale problems in astrophysics and with a rich phenomenology on those scales. We scrutinize the FD…
Probing Dark Matter Self-interaction with Ultra-faint Dwarf Galaxies
Kohei Hayashi, Masahiro Ibe, Shin Kobayashi +2
Self-interacting dark matter (SIDM) has gathered growing attention as a solution to the small scale problems of the collisionless cold dark matter (DM). We investigate the SIDM usi…
Diversity of dark matter density profiles in the Galactic dwarf spheroidal satellites
Kohei Hayashi, Masashi Chiba, Tomoaki Ishiyama
The core-cusp problem is one of the controversial issues in the standard paradigm of cold dark matter (CDM) theory. However, under the assumption of conventional spherical s…
Constraining Primordial Black Holes with Dwarf Galaxy Heating
Philip Lu, Volodymyr Takhistov, Graciela B. Gelmini +3
Black holes formed in the early universe, prior to the formation of stars, can exist as dark matter and also contribute to the black hole merger events observed in gravitational wa…
Formation of massive globular clusters with dark matter and its implication on dark matter annihilation
Henriette Wirth, Kenji Bekki, Kohei Hayashi
Recent observational studies of -ray emission from massive globular clusters (GCs) have revealed possible evidence of dark matter (DM) annihilation within GCs. It is, however, s…
Investigation of the Status of Unit 2 Nuclear Reactor of the Fukushima Daiichi by the Cosmic Muon Radiography
Hirofumi Fujii, Kazuhiko Hara, Shugo Hashimoto +19
We have investigated the status of the nuclear debris in the Unit-2 Nuclear Reactor of the Fukushima Daiichi Nuclear Power plant by the method called Cosmic Muon Radiography. In th…
EMPRESS. III. Morphology, Stellar Population, and Dynamics of Extremely Metal Poor Galaxies (EMPGs): Are EMPGs Local Analogs of High- Young Galaxies?
Yuki Isobe, Masami Ouchi, Takashi Kojima +16
We present the morphology and stellar population of 27 extremely metal poor galaxies (EMPGs) at with metallicities of 0.01--0.1 Z. We conduct multi-component sur…
N-body self-consistent stars-halo modeling of the Fornax dwarf galaxy
Galina Shchelkanova, Kohei Hayashi, Sergei Blinnikov
We present nearly self-consistent stellar-halo models of the Fornax dwarf spheroidal galaxy associated with the Milky Way galaxy. Such galaxies are dominated by dark matter and hav…
Investigation of Unit-1 Nuclear Reactor of the Fukushima Daiichi by Cosmic Muon Radiography
Hirofumi Fujii, Kazuhiko Hara, Kohei Hayashi +11
We have investigated the status of the nuclear fuel assemblies in Unit-1 reactor of the Fukushima Daiichi Nuclear Power plant by the method called Cosmic Muon Radiography. In this…
-factor estimation of Draco, Sculptor and Ursa Minor dwarf spheroidal galaxies with the member/foreground mixture model
Shun-ichi Horigome, Kohei Hayashi, Masahiro Ibe +3
Dwarf spheroidal galaxies (dSphs) are promising targets of indirect detection experiments searching for dark matter (DM) at present universe. Toward robust prediction for the amoun…
Spatial-segregation limit for exclusion processes with two components under unbalanced reaction
Kohei Hayashi
We consider exclusion processes with two types of particles which compete strongly with each other. In particular, we focus on the case where one species does not diffuse at all an…