Carollo, Daniela, Beers, Timothy C., Chiba, Masashi, Norris, John E., Freeman, Ken C., Lee, Young Sun, ...
The structure and kinematics of the recognized stellar components of the Milky Way are explored, based on well-determined atmospheric parameters and kinematic quantities for 32360 "calibration stars"...
Chemical Compositions of Kinematically Selected Outer Halo Stars (2009)
Zhang, Lan, Ishigaki, Miho, Aoki, Wako, Zhao, Gang, Chiba, Masashi
Chemical abundances of 26 metal-poor dwarfs and giants are determined from high-resolution and high signal-to-noise ratio spectra obtained with Subaru/HDS. The sample is selected so that most of the...
On the Size Evolution of a Galactic Disk in Hierarchical Merging of Cold Dark Matter Halos (2009)
Hayashi, Hirohito, Chiba, Masashi
We investigate the dynamical effects of dark matter subhalos on the structure and evolution of a galactic disk, using semi-analytic method that includes approximated and empirical relations as...
Minezaki, Takeo, Chiba, Masashi, Kashikawa, Nobunari, Inoue, Kaiki Taro, Kataza, Hirokazu
We present mid-infrared imaging at 11.7 $\mu$m for the quadruple lens systems, MG0414+0534 and Q2237+030, using the cooled mid-infrared camera and spectrometer (COMICS) attached on the Subaru...
The Extended Star Formation History of the Andromeda Spheroid at 35 Kpc on the Minor Axis (2008)
Brown, Thomas M., Beaton, Rachael, Chiba, Masashi, Ferguson, Henry C., Gilbert, Karoline M., Guhathakurta, Puragra, ...
Using the HST ACS, we have obtained deep optical images reaching well below the oldest main sequence turnoff in fields on the southeast minor-axis of the Andromeda Galaxy, 35 kpc from the nucleus....
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 Galaxy based on a series...
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 for the old stellar...
Dark Matter Substructure in Lensing Galaxies (2008)
Chiba, Masashi, Minezaki, Takeo, Inoue, Kaiki T., Kashikawa, Nobunari, Kataza, Hirokazu, Sugai, Hajime
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 sample of quadruple...
Lens Mapping of Dark Matter Substructure with VSOP-2 (2008)
Ohashi, Shigenori, Chiba, Masashi, Inoue, Kaiki Taro
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 subhalos) with masses
Bekki, Kenji, Chiba, Masashi, McClure-Griffiths, N. M.
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 disk. Based on the...
The Magellanic Squall: Gas Replenishment from the Small to Large Magellanic Cloud (2007)
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 between the SMC,...
Massive stars and globular cluster formation (2007)
We first present chemodynamical simulations to investigate how stellar winds of massive stars influence early dynamical and chemical evolution of forming globular clusters (GCs). In our numerical...
A Subaru/Suprime-Cam Survey of M31's spheroid along the South-East minor axis (2007)
Tanaka, Mikito, Chiba, Masashi, Komiyama, Yutaka, Iye, Masanori, Guhathakurta, Puragra
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. Our photometric...
Two stellar components in the halo of the Milky Way (2007)
Carollo, Daniela, Beers, Timothy C., Lee, Young Sun, Chiba, Masashi, Norris, John E., Wilhelm, Ronald, ...
The halo of the Milky Way provides unique elemental abundance and kinematic information on the first objects to form in the Universe, and this information can be used to tightly constrain models of...
Dynamical Effects of CDM Subhalos on a Galactic Disk (2006)
Hayashi, Hirohito, Chiba, Masashi
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. Our particular...
Dynamical Influences of the Last Magellanic Interaction On the Magellanic Clouds (2006)
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 Clouds for the last...
Direct Detection of Intermediate Mass Compact Objects via Submillilensing (2005)
Inoue, Kaiki Taro, Chiba, Masashi
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 subhalos. We propose...
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 triggering star...
Dark and stellar matter in strong lensing galaxies from a joint lensing and stellar dynamics (2005)
Hamana, Takashi, Ohyama, Youichi, Chiba, Masashi, Kashikawa, Nobunari
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 dispersion of the lensing...
Fossil records of cosmic reionization in galactic stellar halos (2005)
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 distributions of old...
Chiba, Masashi, Minezaki, Takeo, Kashikawa, Nobunari, Kataza, Hirokazu, Inoue, Kaiki Taro
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 the Subaru telescope....
Three-dimensional Mapping of CDM Substructure at Submillimeter Wavelengths (2005)
Inoue, Kaiki Taro, Chiba, Masashi
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 $\lesssim 10^8 \ms$. To...
Three-dimensional Mapping of CDM Substructure at Submillimeter Wavelengths (2005)
Inoue, Kaiki Taro, Chiba, Masashi
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 $\lesssim 10^8 \ms$. To...
Three-dimensional Mapping of CDM Substructure at Submillimeter Wavelengths (2005)
Inoue, Kaiki Taro, Chiba, Masashi
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 $\lesssim 10^8 \ms$. To...
Three-dimensional Mapping of CDM Substructure at Submillimeter Wavelengths (2005)
Inoue, Kaiki Taro, Chiba, Masashi
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 $\lesssim 10^8 \ms$. To...
Three-dimensional Mapping of CDM Substructure at Submillimeter Wavelengths (2005)
Inoue, Kaiki Taro, Chiba, Masashi
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 $\lesssim 10^8 \ms$. To...
The Surprisingly Steep Mass Profile of Abell 1689, from a Lensing Analysis of Subaru Images (2004)
Broadhurst, Tom, Takada, Masahiro, Umetsu, Keiichi, Kong, Xu, Arimoto, Nobuo, Chiba, Masashi, ...
Subaru observations of A1689 (z=0.183) are used to derive an accurate, model-independent mass profile for the entire cluster, r
Extended Source Effects in Substructure Lensing (2004)
Inoue, Kaiki Taro, Chiba, Masashi
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 consider a lens...
On the Kinematics of Tidal Debris from Omega Cen's Progenitor Galaxy (2004)
Chiba, Masashi, Mizutani, Arihiro
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 cluster, omega...
Formation of giant globular cluster G1 and the origin of the M31 stellar halo (2004)
We first demonstrate that globular cluster G1 could have been formed by tidal interaction between M31 and a nucleated dwarf galaxy (dE,N). Our fully self-consistent numerical simulations show that...
Explaining the mysterious age gap of globular clusters in the Large Magellanic Cloud (2004)
Beasley, Michael Andrew, Bekki, Kenji, Chiba, Masashi, Couch, Warrick J., Da Costa, Gary Stewart, Forbes, Duncan Alan, ...
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 ago. It is not clear what...
Explaining the mysterious age gap of globular clusters in the Large Magellanic Cloud (2004)
Bekki, Kenji, Couch, Warrick J., Beasley, Michael A., Forbes, Duncan A., Chiba, Masashi, Da Costa, Gary S.
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 ago. It is not clear what...
Explaining the mysterious age gap of globular clusters in the Large Magellanic Cloud (2004)
Bekki, Kenji, Couch, Warrick J., Beasley, Michael A., Forbes, Duncan A., Chiba, Masashi, Da Costa, Gary S.
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 ago. It is not clear what...
Explaining the mysterious age gap of globular clusters in the Large Magellanic Cloud (2004)
Bekki, Kenji, Couch, Warrick J., Beasley, Michael A., Forbes, Duncan A., Chiba, Masashi, Da Costa, Gary S.
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 ago. It is not clear what...
Explaining the mysterious age gap of globular clusters in the Large Magellanic Cloud (2004)
Bekki, Kenji, Couch, Warrick J., Beasley, Michael A., Forbes, Duncan A., Chiba, Masashi, Da Costa, Gary S.
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 ago. It is not clear what...
Direct Mapping of Massive Compact Objects in Extragalactic Dark Halos (2003)
Inoue, Kaiki Taro, Chiba, Masashi
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 for such compact...
Kinematics of Tidal Debris from Omega Centauri's Progenitor Galaxy (2003)
Mizutani, Arihiro, Chiba, Masashi, Sakamoto, Tsuyoshi
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 globular cluster,...
The Mass of the Milky Way: Limits from a Newly Assembled Set of Halo Objects (2002)
Sakamoto, Tsuyoshi, Chiba, Masashi, Beers, Timothy C.
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 the Galaxy, their...
ERO R1 in CL0939+4713 field - Evidence for an S0-like galaxy at z \sim 1.5 (2002)
Iye, Masanori, Shimasaku, Kazuhiro, Miyazaki, Satoshi, Imanishi, Masatoshi, Kashikawa, Nobunari, Kodama, Tadayuki, ...
We present further observations of the extremely red object ERO J094258+4659.2, identified by \citet{iye00} as ERO R1 in their deep images of the cluster A851. We estimate its redshift independently...
Beers, Timothy C., Drilling, John S., Rossi, Silvia, Chiba, Masashi, Rhee, Jaehyon, Fuhrmeister, Birgit, ...
We report medium-resolution (1-2 A) spectroscopy and broadband (UBV) photometry for a sample of 39 bright stars (the majority of which are likely to be giants) selected as metal-deficient candidates...
Ohyama, Youichi, Hamana, Takashi, Kashikawa, Nobunari, Chiba, Masashi, Futamase, Toshifumi, Iye, Masanori, ...
We present new optical spectroscopy of the lens elliptical galax in the ``Einstein Cross'' lens system HST 14176+5226, using the Faint Object Camera and Spectrograph (FOCAS) of the Subaru t Our...
Formation of the Galactic disk globular clusters in early dissipative minor merging (2002)
The origin of metal-rich, highly flattened, and rapidly rotating disk globular cluster system in the Galaxy is one of longstanding issues in the context of the Galaxy formation. Our numerical...
On the origin of metallicity in Lyman-alpha forest systems (2002)
Chiba, Masashi, Nath, Biman B.
Restricted Access. Cosmic chemical evolution. Proceedings of the 187th Symposium of the International Astronomical Union, held at Kyoto, Japan, 26-30 August 1997. Eds. K. Nomoto and J. W. Truran....
Probing Dark Matter Substructure in Lens Galaxies (2001)
We investigate the effects of numerous dark matter subhalos in a galaxy-sized halo on the events of strong lensing, to assess their presence as expected from the cold dark matter scenario. Lens...
Sunyaev-Zel'dovich distortion from early galactic winds (2001)
Majumdar, Subhabrata, Nath, Biman B, Chiba, Masashi
We consider the distortion in the cosmic microwave background (CMB) resulting from galactic winds at high redshift. Winds outflowing from galaxies have been hypothesized to be possible sources of...
Formation of the Galactic stellar halo I. Structure and kinematics (2001)
We perform numerical simulations for the formation of the Galactic stellar halo, based on the currently favored cold dark matter (CDM) theory of galaxy formation. Our numerical models, taking into...
Sunyaev-Zel'dovich distortion from early galactic winds (2001)
Majumdar, Subhabrata, Nath, Biman B., Chiba, Masashi
Sorry, the full text of this article is not available here. Please click on the alternative location to access it.
Beers, Timothy C., Chiba, Masashi
We present a review of recent studies of the formation and evolution of the Milky Way galaxy, in particular based on large samples of non-kinematically selected stars with available proper motions....
Sunyaev-Zel'dovich distortion from early galactic winds (2001)
Majumdar, Subhabrata, Nath, Biman B, Chiba, Masashi
We consider the distortion in the cosmic microwave background (CMB) resulting from galactic winds at high redshift. Winds outflowing from galaxies have been hypothesized to be possible sources of...
On the origin of metallicity in Lyman-alpha forest systems (2001)
Chiba, Masashi, Nath, Biman B.
Restricted Access. Cosmic chemical evolution. Proceedings of the 187th Symposium of the International Astronomical Union, held at Kyoto, Japan, 26-30 August 1997. Edited by K. Nomoto and J. W....
Sunyaev-Zel'dovich distortion from early galactic winds (2000)
Majumdar, Subhabrata, Nath, Biman, Chiba, Masashi
We consider the distortion in the cosmic microwave background (CMB) due to galactic winds at high redshift. Winds outflowing from galaxies have been hypothesized to be possible sources of metals in...
Stellar Kinematics of the Spiral Structure in the Solar Neighborhood (2000)
Yano, Taihei, Chiba, Masashi, Gouda, Naoteru
We present a method, based on the kinematic analysis of the Galactic disk stars, to clarify whether the internal motions of the stellar system in spiral arms follow those expected in the density wave...
Structure of the Galactic Stellar Halo Prior to Disk Formation (2000)
Chiba, Masashi, Beers, Timothy C.
We develop a method for recovering the global density distribution of the ancient Galactic stellar halo prior to disk formation, based on the present orbits of metal-poor stars observed in the solar...
Formation of the Galactic stellar halo. Origin of the metallicity-eccentricity relation (2000)
Motivated by the recently improved knowledge on the kinematic and chemical properties of the Galactic metal-poor stars, we present the numerical simulation for the formation of the Galactic stellar...
New limits on a cosmological constant from statistics of gravitational lensing (1998)
Chiba, Masashi, Yoshii, Yuzuru
We present new limits on cosmological parameters from the statistics of gravitational lensing, based on the recently revised knowledge of the luminosity function and internal dynamics of E/S0...
Three-dimensional orbits of metal-poor halo stars and the formation of the Galaxy (1997)
Chiba, Masashi, Yoshii, Yuzuru
We present the three-dimensional orbital motions of metal-poor stars in conjunction with their metal abundances, for the purpose of getting insight into the formation process of the Galaxy. Our...
On The Origin Of Metallicity In Lyman-Alpha Forest Systems (1997)
Chiba, Masashi, Nath, Biman B.
We investigate the hypothesis that $\lyal$ absorption lines arise in two populations of halos --- minihalos of small circular velocity ($V_c \la 55$ km s$^{-1}$) in which star formation and metal...
DWARF GALAXIES AND THE ORIGIN OF INTRACLUSTER MEDIUM (1995)
Nath, Biman B., Chiba, Masashi
Following the recent suggestion that it is dwarf galaxies in clusters -- as opposed to large ellipticals -- that provide the intracluster gas, we estimate the metallicity of the intracluster medium...
Protogalactic evolution and magnetic fields (1994)
We show that the relatively strong magnetic fields ($\ge 1 \mu$G) in high redshift objects can be explained by the combined action of an evolving protogalactic fluctuation and electrodynamic...
A Technique Fof Determining the Extragalactic Distance Scale (1994)
Chiba, Masashi, Yoshii, Yuzuru
We propose a method of distance determination based on the internal structure and dynamics of disk galaxies. The method relies on the universal luminosity profile of a stellar disk represented by an...
Effects of Photoionization on Galaxy Formation (1994)
Chiba, Masashi, Nath, Biman B.
We investigate the effects of the observed UV background radiation on galaxy formation. Photoionization by UV radiation decreases the cooling rate of the gas in halos, so that objects with only large...