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Origin of structural and kinematical properties of the Small Magellanic Cloud
Kenji Bekki, Masashi Chiba
We investigate structural, kinematical, and chemical properties of stars and gas in the Small Magellanic Cloud (SMC) interacting with the Large Magellanic Cloud (LMC) and the Galax…
Formation of the Small Magellanic Cloud: ancient major merger as a solution to the kinematical differences between old stars and HI gas
Kenji Bekki, Masashi Chiba
Recent observations of the Small Magellanic Cloud (SMC) have revealed that the HI gas shows a significant amount of rotation (V_c 60 km/s), while no or little rotation is evident f…
Dark Matter Substructure in Lensing Galaxies
Masashi Chiba, Takeo Minezaki, Kaiki T. Inoue +3
To set useful limits on the abundance of small-scale dark matter halos (subhalos) in a galaxy scale, we have carried out mid-infrared imaging and integral-field spectroscopy for a…
Lens Mapping of Dark Matter Substructure with VSOP-2
Shigenori Ohashi, Masashi Chiba, Kaiki Taro Inoue
Hierarchical clustering models of cold dark matter (CDM) predict that about 5% - 10% of a galaxy-sized halo with mass ~ 10^12 solar masses (M_sun) resides in substructures (CDM sub…
The Magellanic impact: Collision between the outer Galactic HI disk and the leading arms of the Magellanic stream
Kenji Bekki, Masashi Chiba, N. M. McClure-Griffiths
We show that collisions between the outer Galactic HI disk and the leading arms (LAs) of the Magellanic stream (MS) can create giant HI holes and chimney-like structures in the dis…
The Magellanic Squall: Gas Replenishment from the Small to Large Magellanic Cloud
Kenji Bekki, Masashi Chiba
We first show that a large amount of metal-poor gas is stripped from the Small Magellanic Cloud (SMC) and fallen into the Large Magellanic Cloud (LMC) during the tidal interaction…
Two Stellar Components in the Halo of the Milky Way
D. Carollo, T. C. Beers, Y. S. Lee +9
The halo of the Milky Way provides unique elemental abundance and kinematic information on the first objects to form in the Universe, which can be used to tightly constrain models…
Massive stars and globular cluster formation
Kenji Bekki, Masashi Chiba
We first present chemodynamical simulations to investigate how stellar winds of massive stars influence early dynamical and chemical evolution of forming globular clusters (GCs). I…
A Subaru/Suprime-Cam Survey of M31's spheroid along the South-East minor axis
Mikito Tanaka, Masashi Chiba, Yutaka Komiyama +2
We have used Suprime-Cam on the Subaru Telescope to conduct a V- and I-band imaging survey of fields sampling the spheroid of the Andromeda galaxy along its south-east minor axis.…
Dynamical Effects of CDM Subhalos on a Galactic Disk
Hirohito Hayashi, Masashi Chiba
We investigate the dynamical interaction between a galactic disk and surrounding numerous dark subhalos as expected for a galaxy-sized halo in the cold dark matter (CDM) models. Ou…
Dynamical Influences of the Last Magellanic Interaction On the Magellanic Clouds
Kenji Bekki, Masashi Chiba
We investigate the present distributions of gas and young stars in the Large and Small Magellanic Clouds (LMC and SMC) based on fully self-consistent numerical simulations of the C…
Direct Detection of Intermediate Mass Compact Objects via Submillilensing
Kaiki Taro Inoue, Masashi Chiba
A galaxy-sized halo may contain a large number of intermediate mass (10^{2-4} solar mass) compact objects (IMCOs), which can be intermediate mass black holes (IMBHs) or the CDM sub…
Impact of dark matter subhalos on extended HI disks of galaxies: Possible formation of HI fine structures and stars
Kenji Bekki, Masashi Chiba
Recent observations have discovered star formation activities in the extreme outer regions of disk galaxies. However it remains unclear what physical mechanisms are responsible for…
Dark and stellar matter in strong lensing galaxies from a joint lensing and stellar dynamics
Takashi Hamana, Youichi Ohyama, Masashi Chiba +1
We present Subaru spectroscopy of the early-type lensing galaxies in the lens systems HST14113+5211 (z=0.464) and B2045+265 (z=0.868), being aimed at measuring the velocity dispers…
Fossil records of cosmic reionization in galactic stellar halos
Kenji Bekki, Masashi Chiba
Galactic stellar halos have long been considered to contain fossil information on early dynamical and chemical evolution of galaxies. We propose that the surface brightness distrib…
Subaru Mid-infrared Imaging of the Quadruple Lenses PG1115+080 and B1422+231: Limits on Substructure Lensing
Masashi Chiba, Takeo Minezaki, Nobunari Kashikawa +2
We present mid-infrared imaging at 11.7 mu m for the quadruple lens systems, PG1115+080 and B1422+231, using the cooled mid-infrared camera and spectrometer (COMICS) attached on th…
Three-dimensional Mapping of CDM Substructure at Submillimeter Wavelengths
Kaiki Taro Inoue, Masashi Chiba
The cold dark matter (CDM) structure formation model predicts that about 5-10 percent of a typical galactic halo of mass $\sim 10^{12} \ms$ is in substructures with masses $\lesssi…
Formation and evolution of the Magellanic Clouds. I.Origin of structural, kinematical, and chemical properties of the Large Magellanic Cloud
K. Bekki, M. Chiba
We investigate the dynamical and chemical evolution of the Large Magellanic Cloud (LMC) interacting with the Galaxy and the Small Magellanic Cloud (SMC) based on a series of self-c…
Extended Source Effects in Substructure Lensing
Kaiki Taro Inoue, Masashi Chiba
We investigate the extended source size effects on gravitational lensing in which a lens consists of a smooth potential and small mass clumps (``substructure lensing''). We first c…
Explaining the mysterious age gap of globular clusters in the Large Magellanic Cloud
K. Bekki, W. J. Couch, M. A. Beasley +3
The Large Magellanic Cloud (LMC) has a unique cluster formation history in that nearly all of its globular clusters were formed either 13 Gyr ago or less than 3 Gyr a…
On the Kinematics of Tidal Debris from Omega Cen's Progenitor Galaxy
Masashi Chiba, Arihiro Mizutani
The kinematic properties of tidal debris from an orbiting Galactic satellite is presented, on the assumption that its central part once contained the most massive Galactic globular…
Direct Mapping of Massive Compact Objects in Extragalactic Dark Halos
Kaiki Taro Inoue, Masashi Chiba
A significant fraction of non-baryonic or baryonic dark matter in galactic halos may consist of MASsive Compact Objects (MASCOs) with mass M=10^{1-4}M_{sun}. Possible candidates fo…
Kinematics of Tidal Debris from Omega Centauri's Progenitor Galaxy
Arihiro Mizutani, Masashi Chiba, Tsuyoshi Sakamoto
We present the kinematic properties of a tidally disrupted dwarf galaxy in the Milky Way, based on the hypothesis that its central part once contained the most massive Galactic glo…
The Mass of the Milky Way: Limits from a Newly Assembled Set of Halo Objects
Tsuyoshi Sakamoto, Masashi Chiba, Timothy C. Beers
We set new limits on the mass of the Milky Way, making use of the latest kinematic information for Galactic satellites and halo objects. In order to bind these sample objects to th…