First-Generation Objects in the Universe

 Aoki Wako (NAOJ)
"Subaru/HDS observations for metal-deficient stars" 

 Our studies on elemental abundances for metal-deficient stars with
 Subaru/HDS in these two years are reviewed. 
 First topic is the discovery of C,N,O, and Mg-rich, Fe-deficient 
 ([Fe/H]=-3.7) object CS29498-043, and its impact on the studies of 
 the nucleosynthesis in supernovae and the origin of carbon-rich, 
 very metal-deficient stars. Studies of neutron-capture 
 (r- and s-process) elements extended to the heaviest elements 
 (Pb, Th, and U) are briefly reviewed. 
 Challenges for the analysis of isotope abundances for a few elements 
 are reported.   


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 Beers Timothy, C. (Michigan Univ.) 
 "Observations on halo stars" 

  N.A.


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 Bromm Volker (CfA) 
 "Observations on halo stars" 

 N.A.


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 Enoki Motohiro (NAOJ, Osaka Univ.) 
 "Relations between Galaxy Formation and the Environments of Quasars"
 
We investigate the environments of quasars using a semi-analytic 
model which includes both galaxy and quasar formations. 
We assume that a supermassive black hole is fueled by the accretion 
of gas during a major merger of galaxies. 
Using this model,  the environments of quasars. 
The results of our model show that the spatial distribution of galaxies 
is different from that of quasars. 
Furthermore, we found that at 0.2 < z < 0.5 most quasars are likely to 
reside in galaxy groups. 
On the other hand, at 1 < z < 2 most quasars seem to reside in environments 
ranging from small groups of galaxies to clusters of galaxies. 


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 Fujimoto Masayuki (Hokkaido Univ.)
 "Evolution of metal-deficient stars"
 
N.A.
 

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 Hanami Hitoshi (Iwate Univ.)
 "Multimodal Galactic Starbursts and Cosmic Star Formation History"
 
Dusty SED diagnostics is performed for various starburst galaxies 
including high-z submm galaxies. high-z submm galaxies are much more 
active than local ULIRGs, however, their surface brightness is lower 
than that of local ULIRGs. 
It indicates that the IMF of high-z submm galaxies are flat. 
This IMF can also reproduce the present color-magnitude relation of 
present elliptical galaxies.  
Thus, the submm galaxies can be the progenitor of present elliptical 
galaxies, which is in starburst phase.        
 

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 Hayashino Tomoki (CNRS, Tohoku Univ.)
 "Discovery of a "Giant Galaxy-Forming Region" at z=3.1 I. The whole aspects of the structure and bias parameter"
 
We have discovered large scale structure at z=3.09 consists of Ly-alpha 
emitters, Ly-alpha absorbers and extended Ly-alpha sources, in narrowband 
imaging survey with the Subaru prime focus camera(Suprime-cam).
The large scale structure discovered has belt-like form 60Mpc long 
by 20Mpc wide.  Bias parameter of this high-density region is estimated 
to be about "6", compared with the other field at the same redshift, which 
is considered to be a blank field. 
Among many Ly-alpha objects in this large structure, a lot of extended 
Ly-alpha sources found along the belt-like structure are remarkable. 
They are possible candidates of proto-galaxies in early phases. 
This region which contains so many Ly-alpha objects should be called as 
"Giant Galaxy-Forming Region". 
In this talk, the whole aspects of the "Giant Galaxy-Forming Region" will 
be presented.  
 

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 Hiroi Kumiko (Univ. Tsukuba)
 "A constraint by z \sim 6 QSO spectra on cosmic reionization and galaxy formation"
 
We simulate quasar absorption line spectra using the radiative transfer 
calculations on the reionization in an inhomogeneous universe.
By confronting the generated spectra with the Ly-alpha absorption lines 
of recently observed z \sim 6 QSOs, we attempt to derive the ionization level, 
the intensity of UV background radiation, and the fraction of 
self-shielded regions.
Based on these results, we discuss some implications for galaxy formation.
 

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 Honda Satoshi (NAOJ)
 "Abundance Patterns in Very Metal-Poor Stars"
 
We obtained high resolution, high quality spectra of 22 very metal-poor 
stars with Subaru/HDS for detailed abundance studies of neutron-capture 
elements, and detected Th in seven objects in our sample.
We will discuss the relative abundances of neutron-capture elements, 
dispersion of the abundance ratios, and the impact on the cosmochronology 
using Th.
 

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 Inoue Akio (Kyoto Univ.)
 "Constraint on intergalactic dust from thermal history of intergalactic medium"
 
We present a new constraint on the amount of the intergalactic dust 
at high redshift. 
It is determined via the comparison between the theoretical thermal 
history of the intergalactic gas by taking account of the photoelectric 
heating by dust grains and the observational thermal history of 
Lyman alpha forest.
The photoelectric heating by dust can be the most important heating 
mechanism for the intergalactic medium. 
As a result, we obtain an upper limit of the intergalactic dust-to-gas ratio, 
extinction, and reddening as a function of typical size of the intergalactic 
grains.
 

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 Ioka Kunihito (Osaka Univ.)
 "Theories on GRBs"
 
We will review the recent progress in the theories on GRBs. 
We will focus attention on the high redshift GRBs. 
The topics will be the redshift distribution of GRBs, the redshift 
indicators of GRBs, the relation with the first generation objects,
the relation with the star formation rate and so on.
We may also refer to the X-ray flashes, a new class of X-ray transients
which has been recently recognized as a phenomenon related to GRBs.
 

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 Ishimaru Yuhri (Ochanomizu Univ.)
 "First Enrichment of our Galaxy"
 
Observations of metal-poor stars show large dispersions in their 
chemical abundances. 
This may indicate that these stars are enriched by only one or 
a few supernovae, since the inter-stellar gas was not mixed enough
at the early epoch. 
We construct an inhomogeneous chemical evolution model, and compare 
predicted stellar abundance distributions for O--Zn with observations. 
Using statistical method, we show clear differences depending on 
nucleosynthesis data. 
We also discuss the origin of r-process elements, comparing models 
with the new data of Eu, Ba, and Sr abundance in extremely metal-poor 
stars obtained by recent our observations of Subaru HDS.
 

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 Iwamoto Nobuyuki (NAOJ)
 "Nucleosynthesis in zero-metal, intermediate-mass AGB stars"
 
Recent observations have discovered very metal-poor stars with carbon
and nitrogen enrichment. 
Except for the self-pollution of low-mass, very metal-poor stars, natural 
astrophysical sites of these elements are asymptotic giant branch stars. 
In particular, intermediate-mass stars have relatively short lifetime 
and thus are one of the sites of primordial carbon and nitrogen. 
We followed the evolution of 7-12Msun zero-metal stars and found that 
these stars have C/O > 1 and high nitrogen abundance. 
Lithium is also created, but the duration of super Li-rich phase is 
very short. 
 

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 Iwata Ikuru (Kyoto Univ.) 
 "Lyman Break Galaxies at z ~ 5"
 
We report the first results of our search for Lyman break galaxies
(LBGs) at z ~ 5. 
Using Subaru Prime Focus Camera, we made a deep imaging of 
a 618 square-arcmin field including the Hubble Deep Field.
We detect 310 LBG candidates with Ic < 25.5 Vega mag.
The UV luminosity function of LBGs at z ~ 5 shows no significant
difference from those at z ~ 3 to 4.
We discuss the evolution process of LBGs, as well as the cosmic star 
formation history and the contribution of star-forming galaxies to 
the reionization of intergalactic medium.
 

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 Kamaya Hideyuki (Kyoto Univ.) 
 "Observational possibility of primordial celestial bodies suffering HD cooling"
 
If HD cooling is efficient for the evolution of primordial celestial bodies, 
its effect can be imprinted in their star formation (SF) or SF-history. 
We try to reveal its necessary condition, first of all.
Indeed, it is possible for HD to form if H2 molecule is abundant.
This condition realizes when the virial temperature of the system is 
larger than 10^4 K if ISM thermalizes. 
In this standing point, we examine the abundance evolution of HD in 
an interstellar cloud under the isobaric condition. 
According to our numerical results of primordial chemical network, 
the abundance of HD becomes about 10^{-6}.
Observational implication is also presented. 
If only one percent of the ISM is such clouds, the expected flux is about 
micro-Jy level which is detectable for ALMA project.
 

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 Kawakatsu Nozomu (CCP, Univ. Tsukuba 
 "QSO Formation;Coevolution of Bulge and Nucleus"
 
A new picture for QSO formation is proposed based on the 
radiation-hydrodynamic model for the black hole growth, including 
chemical evolution of the early-type host galaxy.
In our model, two key conditions are necessary for QSO formation;
one is the existence of starburst epoch and the other is that of 
optically thick ISM. 
Thus, the high redshift QSO with z > 6  can be formed if QSO hosts 
satisfy only these two conditions.
Also, we discuss a formation epoch of the first QSOs.
 

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 Kodama Tadayuki (NAOJ) 
 "Star formation history and chemical evolution of dwarf spheroidals"
 
I will review the recent understanding of the formation and evolution 
of dwarf spheroidal galaxies from their chemical abundance pattern and 
the star distribution on the color-magnitude diagrams. 
I will relate these properties to those of the Milky Way and discuss 
whether the dwarf satellites are the "building blocks" of our Galaxy.
 

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 Matsuda Yuichi (Tohoku Univ.) 
 "Discovery of a "Giant Galaxy-Forming Region" at z=3.1 III. Some properties of extended Lyman alpha sources"
 
We report properties of extended emission line sources which have been 
detected in our very deep Lyman alpha imaging survey at redshift z=3.09 
in SSA22 field with Suprime-Cam. 
Since our images are about 0.5 magnitudes deeper and 12 times wider than 
the previous images obtained by Steidel et al., we have discovered a few 
tens extended emission line sources in the field. 
Also we revealed the inner structure of the two bright Lyman alpha "Blobs" 
previously discovered by Steidel et al..
We will examine several explanations for their extended sources including 
Steidel's Blobs.
 

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 Mizusawa Hiromi (Niigata Univ.) 
 "H_2 lines of the first-generation stars"
 
We study the formation process of the first-generation stars. 
Especially, we estimate the luminosities of H_2 lines, which can be 
characteristics of the first-generation star formation process.
We evaluate the time evolution of the line luminosities not only for 
the core collapse phase but also for the mass accretion phase.
The luminosities of the typical lines become the peak at the accretion phase.
For the collapse phase, the strongest lines are pure rotational lines. 
But for the accretion phase, some vibrational lines overwhelm those lines.
We also discuss the detectability of H_2 lines by next generation Infrared 
Satellite, SPICA. 
 

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 Mori Masao (Senshu Univ.)
 "Initial Multiple Supernova explosions in a primordial galaxy"
 
We present results from three-dimensional numerical simulations of 
the dynamics of SN-driven bubbles in a primordial galaxy. 
The incomplete mixing of the ISM during the assembly of massive galaxy 
plays a decisive role in the early enrichment of the metal-poor gas. 
These abundance inhomogeneities would lead to different element abundance 
patterns in extremely metal-deficient stars.
 

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 Murakami Toshio (Kanazawa Univ.)
 "Detectability of GRBs at high redshifts"
 
GRBs are the best tool to explore the earliest universe. 
In fact, the most remote one, which has known distance, is z=4.5 and 
many unknown are expected which show more than z $B!A(B10. 
This enables us to estimate the earliest universe.
 

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 Nagashima Masahiro (NAOJ) 
 "Numerical Galaxy Catalogue"
 
We construct a galaxy formation model by using an N-body/semi-analytic
approach based on the hierarchical clustering scenario.  
The resolved mass of dark halos in the N-body simulation is less than 
10^11M_sun, which denotes the mass deviating from a power law, and which 
is one order of magnitude smaller than previous works such as the Virgo
consortium. 
We show that the resolution is essential to determine the faint-end slope 
of the galaxy luminosity function. 
Now we can present a numerical galaxy catalogue constructed by our model, 
which will be a useful tool to understand observed galaxy properties by 
comparison.
 

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 Nakamura Fumitaka (Niigata Univ.) 
 "IMF in primordial galaxies"
 
 N.A.
 

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 Nakasato Naohito (Univ. Tokyo) 
 "On the Origin of Extremely Metal-Deficient Stars"
 
Using our 3-D hydrodynamical code, we follow the mixing process of 
the material deposited by a supernova explosion.
The used method is same shown in Nakasato & Shigeyama 2000.
As a result of the numerical simulations, we obtain the metallicity 
distribution function of the ISM.
Since material deposited by a SN explosion is diluted by the ISM,
the resulted abundance after the dilution should depend on the density 
of the ISM.
If there are high density filaments or clumps near the site of the SN,
the degree of the pollution at high density regions is less significant 
than low density regions.
By carefully analyzing the resulted metallicity distribution, we will 
show a possible explanation to the extremely metal-deficient star 
discovered recently.
 

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 Nishi Ryoichi (Niigata Univ.) 
 "Formation process of first stars"
 
 N.A.
 

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 Nomoto Ken'ichi (Univ. Tokyo) 
 "Nucleosynthesis in type Ia supernovae"
 
 N.A.
 

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 Nozawa Takaya (Hokkaido Univ.) 
 "Dust in the early universe: Dust formation in the ejecta of primodial supernovae."
 
We investigate formation of dust grains in the ejecta of primordial 
supernovae including pair instability supernovae which are expected 
to occur in the early universe, applying a theory of non-steady-nucleation 
and grain growth.
The results of calculations show that the mass fraction of the ejected gas 
locked into dust grains increases with increasing the mass of progenitors, 
and reaches to 20-30 $\%$ in the pair instability supernovae whose progenitor 
mass ranges from 140 to 260 $M_\odot$.
The size distribution of newly formed grains is approximated by the power law 
whose index ranges from -3.5 to -2.5.
 

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 Omukai Kazu (NAOJ) 
 "Formation of first stars by accretion"
 
The process of star formation from metal-free gas is investigated by 
following the evolution of accreting protostars with emphasis on the 
properties of massive objects. 
The main aim is to establish the physical processes that determine the 
upper mass limit of the first stars. 
Although the consensus is that massive stars were commonly formed in 
the first cosmic structures, our calculations show that their actual 
formation depends sensitively on the mass accretion rate and its time 
variation.
We consider also the sensitivity of the results on the presence of
heavy elements.
 

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 Ouchi Masami (Univ. Tokyo) 
 "Cosmic Reionization and Descendents of High-z Galaxies Probed by 2600 Galaxies at z=3.5-5.2."
 
I will present the results of our high-z galaxy surveys in the Subaru 
Deep Fields (SDFs).
We have detected 2500 Lyman break galaxies (LBGs) at z=3.5-5.2 and 
100 Lyman alpha emitters (LAEs) at z=4.86+/-0.03, some of which have 
spectroscopic redshifts.
The number density of bright LBGs significantly decreases from z=3 to 
z=5, and the faint galaxies are more dominant at z=4-5 than z=3. 
The total UV-luminosity density shows that we have resolved all ionizing 
sources needed for keeping the ionization of IGM at z=4. 
We find that ionizing IGM at z=5 requires a contribution from dwarf galaxies 
whose star-formation rates are ~1 Msol/yr. 
We will discuss implications of ionizing sources at z=6 for the cosmic 
reionization.
We calculate the mass of dark halos hosting these galaxies from the 
correlation lengths, using the analytic models given by Sheth & Tormen (1999). 
We find that these galaxies reside in dark halos with 10^12-10^13.5 Msol, 
and a single dark halo hosts a few galaxies, while a present-day dark halo 
in the same mass range hosts about 1 galaxy. 
These hosting dark halos at z=4-5 will evolve into present-day giant 
ellipticals or galaxy clusters.
 

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 Saigo Kazuya (CCP, Univ. Tsukuba) 
 "The Gravitational Collapse of Primordial Gas Clouds and Its Mass Accretion Rate"
 
We present the evolution of mass accretion rate from the spherically 
collapsing primordial gas clouds by using numerical calculations. 
For simplicity, we neglected the effect of radiation and stellar wind.
The evolution of mass accretion rates weakly depended on its initial 
condition of the clouds until the stellar mass of about 100 Mo and 
have 0.1 Mo/yr.
Our results suggest that the first stars unable to accrete mass after 
the stellar mass of about 100 Mo (Omukai & Palla 2001). 
 

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 Suda Takuma (Hokkaido Univ.) 
 "Evolution of low-mass Population III stars"
 
Computational results for the evolution of low-mass stars without metals 
are presented. 
We discuss about the evolution and the surface chemical composition in 
connection with the mixing phenomena characteristic of the metal-free stars. 
For low-mass stars of 0.9 <= M_sun <= 1.1, the carbon and nitrogen abundances 
in the surface is enhanced by the core helium flash induced mixing and the 
value of C/N becomes around unity. 
It is possible to compare with the recent observations of metal-deficient 
stars by following the subsequent evolution. 
 

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 Sumiyoshi Kohsuke (Numazu College of Technology) 
 "Simulations of collapse-driven supernovae and r-process"
 
We study collapse-driven supernovae and r-process by performing 
simulations of hydrodynamics and nuclear reaction network.
As viable scenarios of r-process, we examine neutrino-driven winds and
prompt explosions. 
Those two scenarios can produce successful r-process abundance patterns 
and may correspond to mass ranges of progenitors.
These scenarios, however, depend on some astrophysical parameters such as
neutron star mass and pressure of outer layer above the wind. 
In order to understand the nucleosynthesis condition more quantitatively 
and the explosion mechanism itself, we are performing numerical simulations 
of core-collapse driven supernovae by GR hydrodynamics with neutrino-transfer. 
We report recent results of simulations of r-process and supernovae.
 

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 Susa Hajime (Rikkyo Univ.) 
 "Formation of primordial dwarf galaxies under UVB"
 
 N.A.
 

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 Suzuki Takeru (NAOJ / Univ. Tokyo) 
 "$^6$Li Production by Cosmic Rays from Structure Formation Shocks -- $^6$Li Archaeology As a Tool to Obtain Proof of the Formation of the Milky Way --"
 
We discuss the production of the element $^6$Li in the early Galaxy by 
cosmic rays accelerated at structure formation shocks, driven by the 
hierarchical merging of sub-Galactic clumps during Galaxy formation.
The salient features of this scenario are discussed and compared with 
observations of $^6$Li in metal-poor halo stars, including a recent 
Subaru HDS result on the star HD140283.
Some unique predictions of the model are clearly testable by future 
observations and may also provide important insight into how our 
Milky Way formed. 
 

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 Tamura Hajime (RCNS, Tohoku Univ.) 
 "Discovery of a "Giant Galaxy-Forming Region" at z=3.1 II. Statistical Properties of Constituents"
 
Investigating young galaxies is essentially important for acquiring the 
knowledge of formation and evolution of galaxies.
We have carried out deep imaging of the field centered on the SSA22a with 
Suprime-Cam applying B,V,R,z', and narrowband filter NB497(CW/BW=4970/80AA).
By comparing narrowband flux with the continuum, we found out 332 candidate 
Ly-alpha emitters and 70 candidate absorbers. 
In this talk, I will discuss statistical properties of galaxies of SSA22 
z=3.1 "Giant Galaxy-Forming Region" such as luminosity function, clustering 
characteristics and so on, compared with the other blank field Ly-alpha 
survey.
 

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 Taniguchi Yoshiaki (Tohoku Univ.) 
 "Observations of High Redshift Galaxies"
 
We give a brief summary of recent progress in the observations of young 
galaxies at high redshift.
In particular, we present  the star formation properties of Ly_alpha 
emission-line galaxies beyond z=5. 
Together with previous studies on galaxies between z=0 and 5, we discuss
 

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 Terasawa Mariko (NAOJ) 
 "Neutrino Effects before and after the Freezeout of the r-Process"
 
We study the effects of neutrino interactions before during and after
the operation of the r-process in the neutrino-energized bubble.  
We find that neutral current and charged current interactions can have
specific unique effects on the final abundances because they continue to
provide a slight neutron exposure even after the freezeout of the r-process. 
We propose that observations of specific elemental and/or isotopic abundances 
in metal-poor stars may be used to identify the neutrino fluxes in operation 
near the freezeout of the r-process.
 

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 Tsuribe Toru (Osaka Univ.) 
 "On the Possibility of Binary Fragmentation during the First Star Formation"
 
This talk will concentrate on the process of gravitational collapse and
fragmentation process during the first star formation before reionization. 
The possibility of binary fragmentation during the first star formation
is discussed by calculating the evolution of nonspherical distortion of 
a collapsing primordial/polytropic cloud core started from almost spherical 
initial configuration with rotation by three-dimensional hydrodynamical 
calculations. 
It is found that the growth rate of nonspherical perturbation is suppressed 
in a collapsing primordial cloud core, different from present-day molecular 
cloud cores, resulting in very low binary formation rate in the first stars.
 

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 Umeda Hideyuki (Univ. Tokyo) 
 "Nucleosynthesis in type II supernovae and hypernovae"
 
We review the characteristics of nucleosynthesis in 'Hypernovae', i.e.,
core-collapse supernovae with very large explosion energies >~ 10^{52} 
ergs and mass M~20-130Msun.
In the hypernova yields the mass ratio between the complete and incomplete 
Si burning regions is larger in hypernovae than normal supernovae. 
As a result, higher energy explosions tend to produce larger [(Zn, Co, V)/Fe] 
and smaller [(Mn, Cr)/Fe], which could explain the trend observed in
extremely metal-poor (EMP) stars. 
On the other hand, the abundances of EMP stars are not consistent with 
pair-instability supernovae (PISNe) with M ~ 140-270Msun.
This result constrain the IMF for the Pop III and EMP stars. 
Hypernovae make important contribution to the early Galactic (and cosmic) 
chemical evolution.
 

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 Wada Keiichi (NAOJ) 
 "Feedback from the First Supernovae in Protogalaxies: The Fate of the Generated Metals"
 
We investigate the chemo-dynamical effects of multiple supernova (SN) 
explosions in primordial galaxies using three-dimensional hydrodynamical 
simulations of the inhomogeneous interstellar medium down to parsec-scales.
We find that the final protogalactic structure and metal distribution
depend strongly on the number of SNe. 
Specifically, 100 SN explosions trigger collapse of the proto-galactic 
cloud followed by formation of a cold, dense clumpy disk with 
Z = 4 x 10^{-4}Z_\odot$, and a chimney-like cavity, whose size is several 
hundred pc and which is relatively metal-rich 
(Z ~ 10^{-3} Z_\odot$--$10^{-2} Z_\odot$). 
Thus, the diffusion of metals from SNe does not proceed homogeneously. 
These results imply that the metallicity of the ``second generation'' of 
stars could be $Z \sim 10^{-4} Z_\odot$, and that the environment to form 
metal-free stars in protogalaxies may be lost relatively quickly 
(< 10^7 yr) after the first burst of Z=0 star formation.  
 

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 Wanajo Shinya (Sophia Univ.) 
 "The r-process in supernovae and U-Th cosmochronology"
 
While the origin of r-process elements remains a long-standing mystery, 
recent spectroscopic studies of extremely metal-poor stars in the Galactic 
halo strongly suggest that it is associated with core-collapse supernovae. 
The r-process nucleosynthesis is examined in the ``neutrino wind'' in
delayed supernova explosions and in the ``prompt explosion'' from 8-10 Msun
supernovae.
A lower limit on the age of the universe is derived by the U-Th chronometer 
pair by comparison with the observation of the highly r-process enhanced,
extremely metal-poor star CS31082-001. 
The inferred age is 14.1 +- 2.4Gyr -- the same between the above two 
different astrophysical sites.
 

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 Yahagi Hideki (NAOJ) 
 "Numerical Tools for the First Generation Objects --- from the first planet to the first cluster of galaxies ---"
 
Two simulation codes expected to be fundamental tools for studying
formation processes of the first-generation objects in various scales
are discussed.
First code is an adaptive mesh refinement N-body code based on the
particle-mesh method, in which the hierarchical meshes are placed
recursively where higher resolution is required. 
Thanks to weak deceleration of gravity calculation due to clustered 
particle configuration, our code is appropriate to simulations for 
statistics of galaxies including the first-generation cluster of galaxies. 
The next code treats the mixture of fluid systems and collisional many 
body systems, and designed originally for the heterogeneous architecture 
computer system at the National Astronomical Observatory consisting of 
VPP5000 and GRAPEs. 
This code is to be applied to studying the dynamical evolution of forming 
star clusters such as the first-generation globular clusters, and accretion 
of planetisimals or gas accretion onto planets in a proto-planetary gas disk.
 

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 Yoshii Yuzuru (Univ. Tokyo) 
 "Chemical evolution of galaxies and galactic nuclei"
 
 N.A.
 

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