SDF Proposed Scientific Goals
(in the order of redshift)
(1)
Search for the cosmic reioniztion features
(PI: Y. Taniguchi)
The origin of the cosmic reioniation has been one of very important
long-standing problems related to the history of the universe. Recent
spectroscopy of very high-z
SDSS quasars with z>5.5
suggest strongly that the trailing edge of the comic reionization may
be z=6 or a bit higher.
However, yet little is known for the origin of the cosmic reionization
soruces. In order to obtain some observational hints, we have proposed
to perform deep imaging survey for cosmic reionization features by
using the NB filter NB921 in
the SDF. We give a brief summary of our
motivation and our strategy.
(2)
Cosmic star formation history viewed from high-
z
Lyα emitters
(PI: Y. Tanigichi)
Much attention has been paid for these years to the cosmic star
formation history (e.g., Madau et al. 1996; Steidel et al. 1999;
Trentham et al. 1999). In the optical regime, observations of Lyman
break galaxies have been used to estimate the cosmic star formation
density beyond z=3. However,
since some forming galaxies could be very strong emission-line
emitters, samples of such popluations must
be taken into account in the estimate of cosmic star formation density.
We
give a summary of recent progress in this research field and then
discuss future strategy based on the SDF data.
(3)
Extended Lyα emitters at high redshift and thier implications
(PI: Y. Taniguchi)
One of the most misterious objects in the high-
z universe is the so-called
Lyα
blobs (LAB) found by Steidel et al. (2000). Two alternative ideas to
explain the origin of LABs have been proposed: (1) Superwind models
(Taniguchi & Shioya 2000; Taniguchi, Shioya, & Kakazu 2001),
and (2) Cooling radiation models
(Fardal et al. 2001). We give a brief summary of the observational
properties
of LABs and then discuss some implications for the understanding of
high-z young galaxies.
(4)
Luminosity properties of Lyman Break
Galaxies at z~4-5 and Lyman
Alpha Emitters at z=5.7
(PI: K. Shimasaku)
We select Lyman Break Galaxies (LBGs) at z∼4-5 and Lyman Alpha
Emitters (LAEs) at z=5.7 from
deep BRiz+NB816 data of the SDF, and study
their luminosity properties. LBGs and LAEs are two major galaxy
populations at high
redshits. The study of LBGs is an extension of a similar study made
based
on the Suprime-Cam GTO data which were about 1 mag shallower. We
estimate UV luminosity for each galaxy and discuss the luminosity
function and the star formation rate distribution of galaxies at
z ≥ 4.
Follow-up spectroscopy and NIR photometry for bright objects are
strongly desired.
(5)
Evolution of clustering of
high-z populations.
(PI: N. Kashikawa)
The evolution of galaxy clustering can put strong constraints on
structure formation models. Especially at
high-z,
the clustering properties of
relatively non-evolved systems at these epochs can be straightforwardly
compared with the model predictions which are basically calculated on
the dark matter halos. Based on the SDF data, we can construct samples
of 2 different high-z pops at
4 different epochs, i.e.,
z=6.5 LAEs,
z=5.7 LAEs,
z=5 LBGs, and
z=4 LBGs.
The most commonly used
statistics auto-angular correlation functions will be derived for these
samples. We will investigate the clustering evolution for each
population LAEs/LBGs combined with previous results for these
populations at lower-z.
We will also derive the cross-correlation function of
z=5 LBGs and
z=4.8 LAEs
at the same redshift,
which would suggests the difference of biasing parameter between these
high-z populations.
(6)
Photometric Redshift Survey for the Largest Scale Structure
at High Redshift
(PI: T. Hayashino)
The Subaru Observatory project in SDF will provide deep multiband
Suprime-Cam images which consist of three NB's(
NB712,
NB816,
NB921)
together with broadbands (
B, R, i', z').
Using these deep
multiband photometric data, we will obtain photometric redshifts of
galaxies with the accuracy of
Δz~0.2 between
z=3.5 and 6,
which corresponds to
~100Mpc/h in comoving length at
z~4
in the case of
(Ω,Λ)=(0.3,0.7) totally flat universe. If
we find two times over density region of
27'x34'xΔ[z=0.3] in our
photometric redshift
survey, which corresponds to
~40x50x150(Mpc/h)^3 at
z=4,
bias parameter will attain to
50-100, which is unphysically large. In
such a case, another origin of structure formation, for example, cosmic
string or domain wall and so on, will be discussed more realistically
and required more seriously.
In this study, photometric redshift simulation is essentially important
to find out such large scale over density region in redshift
distribution
of high z galaxies. We will
estimate intensively accuracy of
photometrically determined redshifts, using real LBG spectra together
with conventional model SEDs as GISSEL96.
(7)
The rest-frame luminosity functions
derived from K'-band selected
galaxy sample
(PI: N. Kashikawa)
NIR band selected samples may provide significant advantages over
optical-band selected samples in studying galaxy evolution due to
smaller extinction by dust and less type-dependent k-corrections at
these wavelengths. Moreover, NIR selection provides samples which are
not biased towards star-forming galaxies
and allows to estimate the mass of galaxies over a wide range of
redshift.
NIR photometry in general improves the estimate of photometric
redshift.
Based on long-base of multi-color
BRi'z'K-data,
a photometric redshift for each sample galaxy can be estimated. In this
phot-z
determined galaxy sample, we will derive (1) redshift distribution of
K-selected
galaxy sample, which can distinguish galaxy formation models (KCtest),
(2)
the rest-frame z'(z=1.5),
i'(z=1.8),
and R(z=2)
and compare them with the
local rest-LFs,
and (3) the rest-frame V(z=3),
and
B(z=4)-LFs
and compare with those
derived from LBG (rest UV
selected)-sample. We will also derive the stellar mass of each galaxy
using the stellar population synthesis and see its evolution and
correlation with other properties.
(8)
Global Star Formation History at
z<1.5
Traced by Halpha and [OII]
(PI: T. Kodama)
NB filters detect not only Ly alpha but OII and Halpha at
lower-z
(z<1.5).
These lines can be discriminated one another on the basis of
multi-colour analysis.
These nebular emission lines
have invaluable information on global star
formation history in the Universe.
Halpha star formation rate is among all
the most important, since it's much less affected by dust extinction.
15hrs integration with
NB921 filter
should able to detect very small amount of star
formation down to 0.03
M_sun/yr
at z=0.4 (10 sigma).
[OII] emission lines will
also sample star formation greater than 1.3
Msun/yr at
z=1.46.
The derived
global star formation rate at
z=0.4
should be directly compared with T. Kodama et al. (Open-use, Sep 2002)
who will map the Halpha star formation rates
in the cluster environment using
N915
filter on Suprime-Cam.
The comparison
will give us a direct measure of the supression of star formation
activity compared to the field.
(9)
A Very Deep Structure Survey using the
Phot-z/Colour-slice technique
(PI: T. Kodama)
The Ri'z' combination is
ideal to search for high density regions (such
as clusters or groups) at
0.3<z<1.2 using the
colour-slice technique
(i.e., search for red sequences of galaxies) and the photometric
redshift
technique. We will then investigate clustering evolution (angular two
point
correlation function) and the environmentally dependent star formation
activities
(colours/magnitudes). Since we reach down to
M*+4 (10 sigma)
even at
z=1,
this data will serve as the deepest optical data-set ever for distant
clusters/groups.
Hence we will be able to address the mass dependent galaxy evolution,
in
particular, we can extend the known trend that the star formation
activity
is higher in less massive galaxies at
lower-z, towards much higher
redshifts
to test the down-sizing hypothesis. The structures thus determined will
be
compared with the weak-lensing analysis to address the degree of bias
between
galaxy and dark matter distributions. This project can be greatly
extended
to even higher redshifts
(z>>1)
with NIR follow-up.
(10)
Evolution of Field Dwarf Galaxies in the SDF
(PI: H. Furusawa)
We propose to study color-split luminosity functions (LFs) of field
galaxies at different redshifts up to
z≅2
based on photo-z, and
discuss evolution of field galaxies, especially for dwarf galaxies
(MB>-17).
The LFs in
the SDF obtained in Garanteed Time Observations, on the basis of
photo-z,
indicates the presence of ~7,000 dwarf galxy candidates and shows a
possible
sign of their evolution (in luminosity or number density) around
z=1.
This
finding roughly supports a theoretical prediction by Babul's group
(Babul & Rees 1992;
Babul & Ferguson 1996, 1998) suggesting that the
formation
epoch of field dwarfs should be
zf=1-1.5.
However, due to limiting
magnitudes
of the GTO data
(i'~26.2, S/N>5),
the sign of evolution in the LFs
is
quite merginal at
z≥1.
We intend to reveal the formation epoch of these
dwarf candidates with the aid of sufficiently deep data obtained in the
Observatory
Project, ~1 mag deeper
(i'>27)
than GTO's. Color-split correlation
functions
of field galaxies, separated into giant and dwarf populations, are also
investigated to understand the spatial environment, where such dwarf
galaxies are born and grow up. This proposal may be thought as a part
of general 'LF studies at intermediate redshifts.'
(11)
Cosmology with High-Redshift Type Ia Supernovae
(PI: M. Doi and N. Yasuda)
We would like to search distant supernovae with Subaru/Suprime-Cam.
Type Ia Supernova (SNIa) is the best known standard candle to study the
expansion of the universe. Current observations indicate accelerating
universe with non-zero cosmological constant. But there are still a few
possible other explanations
such as dust extinction of host galaxies, and evolution of SNIa as a
function
of look back time. Accurate photometry of SNIa at
z=0.8-1.2 is the most
straightforward
way to discriminate the non-zero cosmological constant hypothesis from
other
explanations. Search for SNe is already finished in April and May.
HST/ACS
is now photomerically following up one SNe in the SDF field.
(12)
Mass and Light via weak gravitational lensing
(PI: S. Miyazaki)
Weak lensing provides the most reliable way to estimate the mass in the
universe and enables direct measurement of how lights (galaxies) trace
mass.
Based on Supirme-Cam GTO 2.1 deg2 survey, expected number of
dark
matter
haloes of cluster scale (~1014 solar mass) is several in the
SDF,
which
is not sufficient to make cosmologically significant argument from the
haloes
number count. Using the SDF data, we will take more statistical
approach
instead; we compute the estimate of global mass to light ratio,
M/L, by
dividing
auto correlation of mass distribution with cross correlation of mass
and
light, yielding XXX.
The method is developed by the UH lensing group
and
applied first to their UH8K data. Their conclusion is that
``early type galaxies traces mass with
M/L~250
on scales over 200kpc
(z=0.5) both
in rich cluster enviroments and fields''. This is fairly
puzzling since
they argue that majority of mass is associated with early-type galaxies
even in the field. Independent verification is crucial. Since deep and
multi-color data of the SDF enable both precise estimate of photometric
redshift and accurate classification of types of galaxies, we will be
able to make more quntitative discussion of mass and light in the
universe and to argue the evolution of the
M/L over cosmological time
scale.
(13)
Evolution/Formation of the Hubble Sequence and Galaxy Clustering
(PI: T. Yamada)
- study statistical properties of high-z galaxy clustering
- identify high density region of young galaxies
- study color/molphological properties in fn. of environment
- extremely high-z galaxy abundance
(14)
W/deep CISCO/MOIRCS images
(PI: T. Yamada)
(analysed with previous data in HDF-N/53W002)
- population of faint red galaxies
- evolution of stellar mass distribution and correlation between SF
history/galaxy structure and stellar mass - dusty red galaxies
(15)
Intermediate-z galaxy population
(PI: T. Yamada)
- population of faint old galaxies and large-scale structure
(16)
Gravitational lensing mapping
(PI: T. Yamada)
- search mass concenrationand see M/L distribution
- get test data with deep images to extend the study to SXDF