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