山田 亨

We have searched for absorption in several common atomic species due to the atmosphere or exosphere of the transiting extrasolar planet HD 209458b, using high precision optical spectra obtained with the Subaru High Dispersion Spectrograph (HDS). Previously we reported an Lipper limit on Ha absorption of 0.1% (3 sigma) within a 5.1 angstrom band. Using the same procedure, we now report upper limits on absorption due to the optical transitions of Na D, Li. H alpha, H beta, H gamma, Fe, and Ca. The 3 sigma upper limit for each transition is approximately 1% within a 0.3 angstrom band (the core of the line), and a few tenths of a per cent within a 2 angstrom band (the full line width). The wide-band results are close to the expected limit due to photon-counting (Poisson) statistics, although in the narrow-band case we have encountered unexplained systematic errors at a few times the Poisson level. These results are consistent with all previously reported detections and upper limits, but are significantly more sensitive.

We have started PISCES project; a panoramic imaging and spectroscopic survey of distant clusters on Subaru. It exploits the unique wide-field imaging capability of Suprime-Cam, which provides a 34' x 27' field of view corresponding to a physical area of 16 x 13 Mpc(2) at z similar to 1. We plan to target 15 clusters at 0.4 less than or similar to z less than or similar to 1.3. We report on our first results concerning the inner structures and large-scale structures of two distant clusters at z = 0.55 and 0.83 together with the earlier results on a z = 0.41 cluster. The photometric redshift technique has been applied to multi-color data in order to remove most of the foreground/background galaxies so as to isolate the cluster member candidates. We have found large-scale filamentary structures around the clusters, extending out to > 5 Mpc from the cores, as well as complex inner structures. The galaxy distributions in the inner regions of the clusters look similar to the X-ray intensity maps, suggesting tha. most of the optical structures trace physically bound systems. We also compared the structures of the three clusters with those of model clusters in a numerical simulation (N-body + semi-analytic model) by parameterising the shapes of the iso-density contours of galaxies, and found a broad agreement. Our results that cluster-scale assembly takes place along filaments during hierarchical clustering need to be confirmed spectroscopically in the near future.

We report the discovery of primeval large- scale structures ( LSSs) including two protoclusters in a forming phase at. We carried out extensive deep narrowband imaging in the 1 deg(2) sky of the Subaru/ XMM- Newton Deep at z = 5.7 Field and obtained a cosmic map of 515 Lyalpha emitters ( LAEs) in a volume with a transverse dimension of and a depth of similar to 40 Mpc in comoving units. This cosmic map shows filamentary LSSs, including 180 Mpc x 180 Mpc clusters and surrounding 10 - 40 Mpc scale voids, similar to the present- day LSSs. Our spectroscopic follow- up observations identify overdense regions in which two dense clumps of LAEs with a sphere of 1 Mpc diameter in physical units are included. These clumps show about 130 times higher star formation rate density, mainly due to a large overdensity, similar to 80, of LAEs. These clumps would be clusters in a formation phase involving a burst of galaxy formation.

We present new results of a deep optical imaging survey using a narrow band filter (NB921) centered at lambda = 9196 angstrom together with B, V, R, i', and z' broadband filters in the sky area of the Subaru Deep Field, which has been promoted as one of legacy programs of the 8.2 m Subaru Telescope. We obtained a photometric sample of 58 Ly alpha emitter candidates at z approximate to 6.5-6.6 among similar to 180 strong NB921-excess (z' - NB921 > 1.0) objects together with a color criterion of i' - z' > 1.3. We then obtained optical spectra of 20 objects in our NB921-excess sample, and identified at least nine Ly alpha emitters at z similar to 6.5-6.6, including the two emitters reported by Kodaira et al. (2003, PASJ, 55, L17). Since our Ly alpha-emitter candidates are free from strong amplification of gravitational lensing, we are able to discuss their observational properties from a statistical point of view. Based on these new results, we obtained a lower limit of the star-formation rate density of rho(SFR) similar or equal to 5.7 x 10(-4) h(0.7) M-circle dot yr(-1) Mpc(-3) at z approximate to 6.6, being consistent with our previous estimate. We discuss the nature of star-formation activity in galaxies beyond z = 6.

Using very deep Subaru K'-band imaging and archival Hubble Space Telescope WFPC2/NICMOS data of the Hubble Deep Field-North, we investigate the evolution of the stellar mass, color, and morphology of galaxies to z similar to 3. We mainly examine the rest-frame U-V color distribution of galaxies as a function of stellar mass. At 0.3 less than or similar to z less than or similar to 2, galaxies seem to be divided into the two populations at around the stellar mass of similar to5 x 10(9) M.. The low-mass galaxies have relatively bluer rest-frame U-V color, and their color does not show a clear correlation with stellar mass over the range 10(8) to 5 x 10(9) M.. On the other hand, at higher mass, the more massive galaxies tend to have redder U-V color. The average U-V color of the low-mass galaxies gradually becomes bluer with redshift, from U-V similar to 0.2 at z similar to 0.5 to U-V similar to -0.2 at z similar to 2. However, the correlation between the stellar mass and rest-frame U-V color of the high-mass population does not seem to change significantly between z similar to 0.3 and z similar to 2. The morphological distribution shows that at z less than or similar to 1, the low- mass population is dominated by disk galaxies, while the fraction of early-type galaxies is larger in the high-mass population. At 1 < z < 2, although the fraction of irregular galaxies increases, a similar trend is observed. At z > 2, it is seen that more massive galaxies tend to have redder U-V color over the range 10(9)-10(10) M., although we can only sample galaxies with stellarmass larger than similar to1 x 10(9) M.. These results suggest that the star formation history of galaxies depends greatly on their stellar mass. The low- mass population is likely to have a relatively long star formation timescale, and under the assumption of a constant star formation rate, their formation redshifts do not seem to be much higher than z similar to 2. At stellar masses larger than similar to5 x 10(9) M., there must be some mechanism that suppresses star formation in galaxies at 0 < z < 2.

There are three major axes to describe the evolution of galaxies, namely, time (redshift), space (environment) and mass (stellar mass). In this article, one topic each will be presented along these axes. (1) Based on the Subaru wide-field (30') optical imaging of two distant clusters (z=0.55 and 0.83), we show the large scale structures in galaxy distributions on a scale greater than 10 Mpc, which serve as an evidence for hierarchical growth of rich clusters of galaxies through assembly of surrounding groups. (2) Based on the deep NIR imaging of high-z clusters at z similar to 1 and 1.5, we show massive galaxies in clusters have assembled most of their mass by z = 1.5, which is earlier than the hierarchical model predictions. (3) Based on the Subaru deep and wide optical imaging of Subaru/XMM-Newton Deep Survey Field, we show a deficit of red and faint galaxies and a lack of blue massive galaxies in. the high density regions at z similar to 1, which suggest down-sizing in galaxy formation as apparently opposed to the CDM-based bottom-up scenario.

Based on a co-evolution scenario of massive black holes (MBH) and their host spheroids, we trace the BH growth and the joint cosmic star formation history by ROSAT X-ray All sky surveys. We found: 1) the total amount of star formation associated with MBH growth is at least half of the net star formation at high redshift, which probably missed by the current UV/opt. deep surveys; 2) an upper limit of the abundance ratio of type 2 to type 1 QSOs is about 2, within the constraints of the local BH density, the Chandra hard x-ray deep surveys and the SCUBA counts, 3)the peak redshift of the massive spheroid formation in this case is around 1.5-2.

The Subaru Deep Field (SDF) project is a program of Subaru Observatory to cam, out a deep galaxy survey over a blank field as large as 34' x 27'. The program consists of very deep multi-band optical imaging, near-infrared imaging for smaller portions of the field, and follow-up optical spectroscopy. The major scientific goals of the project are to construct large samples of Lyman-break galaxies at z similar or equal to 4-5 and Lyman alpha emitters at z similar or equal to 5.7 and 6.6, and to make detailed studies of these very high-redshift galaxy populations. In this paper. we describe, the-optical imaging observations and data reduction, presenting mosaicked images and object catalogs in seven bandpasses. The optical imaging was made through five broad-band filters. B, V. R i'. z'. and two narrow-band filters. NB816 (lambda(c) = 8150 Angstrom) and NB921 (lambda(c) = 9196 Angstrom) with almost 10 hour integrations for each band. The limiting magnitudes measured at 3sigma on a 2" aperture are B = 28.45, V =227.74, R = 27.80, i' = 27.43. z' = 26.62. NB816 = 26.63, and NB921 = 26.54 in the AB system. The object catalog constructed for each of the seven bands contains more than 101 objects. The galaxy number counts corrected for detection incompleteness and star-count contributions are found to be consistent with previous results in the literature. Mosaicked images and catalogs of all the bands have been made open to the public on 2004 October 1 oil the SDF project website.

We obtained a deep wide-field (32' x 24') narrowband (lambda(c) = 4977Angstrom, Deltalambda = 77Angstrom) image of a field including the protocluster at z = 3.1 in the SSA22a field studied by Steidel et al. using the Subaru Telescope. The field we observed is about 10 times as large as that studied by Steidel et al. We detected 283 highly confident strong Lyalpha emitter candidates at z similar to 3.1 down to 25.8 AB mag with the observed equivalent width larger than 154 Angstrom. These strong Lyalpha emitter candidates show a highly nonuniform distribution with the beltlike region of high surface density, which is found to extend over similar to60 Mpc in comoving scale. The average number density of the strong Lyalpha emitter candidates in this high-density region is 3 times as high as that of a blank field. The probability of finding such a large-scale high-density peak is as small as 0.1% in the context of the CDM structure formation scenario, if we assume a linear bias parameter b similar to 4. In addition to these strong Lyalpha emitters, we also detected 49 Lyalpha absorbers, which show significant deficit in the narrowband image. We further detected 74 extended emitters, which have significant fluxes over the areas of 18 arcsec(2) or more. Interestingly, both these absorbers and extended emitters show sky distributions very similar to that of the strong Lyalpha emitters. This supports the reality of the large-scale structure at z = 3.1 and suggests that galaxy formation preferentially occurs in the high-density region of strong Lyalpha emitters.

We report on the discovery of a star-forming galaxy at z = 6.33 in the Subaru Deep Field. This object is selected as a candidate of an i'-dropout high-redshift galaxy around z = 6 because of its red i' - z' color in our deep optical imaging survey in the Subaru Deep Field. Our follow-up optical spectroscopy reveals that this object is a strong Lyalpha emitter with only very faint ultraviolet continuum. The rest-frame equivalent width of the detected Lyalpha emission is as much as 130 Angstrom. Thus the light detected in our z' image is largely attributed to the Lyalpha emission, i.e., similar to40% of the z'-band flux is the strong Lyalpha emission, giving a very red i' - z' color. This is consistent with the photometric property of this object because the narrowband data obtained with the NB921 filter show a significant depression, z' - NB921 = -0.54 mag. By using the photometric data, we show that some other objects among the 48 i'-dropout high-redshift galaxy candidates found in the Subaru Deep Field also show a significant NB921 depression. We briefly discuss the nature of these NB921-depressed objects.

We report the properties of 35 robust candidate Lyalpha blobs (LABs), which are larger than 16 arcsec(2) in isophotal area and brighter than 0.7 x 10(-16) ergs s(-1) cm(-2), located in and around the protocluster region at redshift z = 3.1 discovered by Steidel et al. in the SSA22 field, based on wide-field (31' x 23') and deep narrowband (NB497; 4977 Angstrom, FWHM 77 Angstrom) and broadband (B, V, and R) images taken with the prime-focus camera on the Subaru Telescope. The two previously known giant LABs are the most luminous and the largest in our survey volume of 1.3 x 10(5) Mpc(3). We reveal the internal structures of the two giant LABs and discover some bubble-like features, which suggest that intensive starburst and galactic superwind phenomena occurred in these objects in the past. The other 33 LABs have isophotal areas of similar to 16 - 78 arcsec(2) and flux of (0.7-7) x 10(-16) ergs s(-1) cm(-2). These 35 LABs show a continuous distribution of isophotal area and emission-line flux. The distributions of average surface brightness and morphology are widespread from relatively compact high surface brightness objects to very diffuse low surface brightness ones. The physical origins of these LABs may be ( 1) photoionization by massive stars or active galactic nuclei, or ( 2) cooling radiation from gravitationally heated gas, or ( 3) shock heating by starburst-driven galactic superwind. One-third of the LABs are apparently not associated with ultraviolet continuum sources that are bright enough to produce Lyalpha emission, assuming a Salpeter initial mass function. Of these LABs 90% are located inside the high surface density region of the 283 relatively compact and strong Lyalpha emitters selected in our previous study. This suggests that these LABs may be phenomena related to a dense environment at high redshift.

There is evidence that the transiting planet HD 209458b has a large exosphere of neutral hydrogen, based on a 15% decrement in Lyman-alpha flux that was observed by Vidal-Madjar et al. during transits. Here we report upper limits on Halpha absorption by the exosphere. The results are based on optical spectra of the parent star obtained with the Subaru High Dispersion Spectrograph. Comparison of the spectra taken inside and outside of transit reveals no exospheric Ha signal greater than 0.1% within a 5.1Angstrom band (chosen to have the same as the 15% Lyalpha absorption). The corresponding limit on the column density of n = 2 neutral hydrogen is N-2 less than or similar to 10(9) cm(-2). This limit constrains proposed models involving a hot (similar to10(4) K) and hydrodynamically escaping exosphere.

We summarize the multiwavelength properties of X-ray sources detected in the 80 ks XMM-Newton observation of the Groth-Westphal strip, a contiguous strip of 28 Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) images. Among the approximate to150 X-ray sources detected in the XMM-Newton field of view, 23 are within the WFPC2 fields. Ten spectroscopic redshifts are available from the Deep Extragalactic Evolutionary Probe and Canada-France Redshift Survey projects. Four of these show broad Mg II emission and can be classified as type 1 active galactic nuclei (AGNs). Two of those without any broad lines, nevertheless, have [Ne v] emission, which is an unambiguous signature of AGN activity. One is a narrow-line Seyfert 1 and the other a type 2 AGN. As a follow-up, we have made near-infrared spectroscopic observations using the OHS/CISCO spectrometer for five of the X-ray sources for which we found no indication of AGN activity in the optical spectrum. We have detected Halpha + [N II] emission in four of them. A broad Halpha component and/or a large [N II]/Halpha ratio is seen, suggestive of AGN activity. Nineteen sources have been detected in the K-s band, and four of these are extremely red objects (EROs) (I-814 -K-s > 4). The optical counterparts for the majority of the X-ray sources are bulge-dominated. The I-814-K-s color of these bulge-dominated hosts are indeed consistent with evolving elliptical galaxies, while contaminations from star formation/AGNs seems to be present in their V-606-I-814 color. Assuming that the known local relations among the bulge luminosity, central velocity dispersion, and the mass of the central blackhole still hold at z similar to 1, we compare the AGN luminosity with the Eddington luminosity of the central blackhole mass. The AGN bolometric luminosity to Eddington luminosity ratio ranges from 0.3% to 10%.

Despite extensive observational efforts, a convincing optical/infrared identification of the brightest submm source in the Hubble Deep Field, HDF 850.1, has remained elusive after almost four years. This failure is all the more notable given the availability of supporting multifrequency data of unparalleled depth, and subarcsec positional accuracy for the submm/mm source. Consequently, HDF 850.1 has become a test case for the possibility that the most violently star-forming objects in the Universe are too red and/or distant to be seen in the deepest optical images.Here we report the discovery of the galaxy counterpart of HDF 850.1. This object has been revealed by careful analysis of a new, deep K' image of the HDF obtained with the Subaru 8.2-m telescope. Its reality is confirmed by a similar analysis of the HST NICMOS F160W image of the same region. This object is extremely faint (K similar or equal to 23.5), clumpy (on subarcsec scales) and very red (I - K > 5.2; H - K = 1.4 +/- 0.35). The likelihood that it is the correct galaxy counterpart is strongly reinforced by a reanalysis of the combined MERLIN+VLA 1.4-GHz map of the field, which provides a new radio detection of HDF 850.1 only 0.1 arcsec from the new near-infrared counterpart, and with sufficient positional accuracy to exclude all previously considered alternative optical candidates.We have calculated new confidence limits on the estimated redshift of HDF 850.1 in the light of the new radio detection, and find z = 4.1 +/- 0.5. We have also determined the scalelength, and hence estimated the mass of the apparently nearby (0.5 arcsec distant) z similar or equal to 1 elliptical galaxy 3-586.0. From this we calculate that the flux density of HDF 850.1 has been boosted by a factor of similar or equal to3 through gravitational lensing by this intervening elliptical, consistent with predictions that a small but significant fraction of blank-field submm sources are lensed by foreground galaxies. We discuss the wider implications of these results for the submm population and cosmic star formation history.

We use the deep wide-field optical imaging data of the Subaru/XMM-Newton Deep Survey to discuss the luminosity- (mass-)dependent galaxy colours down to z' = 25.0 (5 x 10(9) h(70)(-2) M(circle dot)) for z similar to 1 galaxies in colour-selected high-density regions. We find an apparent absence of galaxies on the red colour-magnitude sequence below z' similar to 24.2, corresponding to similar toM* + 2 (similar to 10(10) M(circle dot)) with respect to passively evolving galaxies at z similar to 1. Galaxies brighter than M* - 0.5 (8 x 10(10) M(circle dot)), however, are predominantly red passively evolving systems, with few blue star-forming galaxies at these magnitudes.This apparent age gradient, where massive galaxies are dominated by old stellar populations while less massive galaxies have more extended star formation histories, supports the 'down-sizing' idea where the mass of galaxies hosting star formation decreases as the Universe ages. Combined with the lack of evolution in the shape of the stellar mass function for massive galaxies since at least z similar to 1, it appears that galaxy formation processes (both star formation and mass assembly) should have occurred in an accelerated way in massive systems in high-density regions, while these processes should have been slower in smaller systems. This result provides an interesting challenge for modem cold dark matter based galaxy formation theories which predict later formation epochs of massive systems, commonly referred to as 'bottom-up'.

An overview of the current status of the 8.2 m Subaru Telescope constructed and operated at Mauna Kea, Hawaii, by the National Astronomical Observatory of Japan is presented. The basic design concept and the verified performance of the telescope system are described. Also given are the status of the instrument package offered to the astronomical community, the status of operation, and some of the future plans. The status of the telescope reported in a number of SPIE papers as of the summer of 2002 are incorporated with some updates included as of 2004 February. However, readers are encouraged to check the most updated status of the telescope through the home page, http://subarutelescope.org/index.html, and/or the direct contact with the observatory staff.

We reported in a previous paper the discovery of a large-scale structure of Lyalpha emitters (LAEs) at z = 4.86 +/- 0.03 with a projected size of 20 h(70)(-1) Mpc x 50 h(70)(-1) Mpc in narrowband data of a 25' x 45' area of the Subaru Deep Field (Ohm(0) = 0.3, lambda(0) = 0.7, and H-0 = 70 h(70) km s(-1) Mpc(-1)). However, the surveyed area, which corresponds to 55 h(70)(-1) Mpc, was not large enough to conclude that what we were seeing was a typical distribution of z similar or equal to 5 LAEs. In this Letter, we report the results of follow-up imaging of the same sky area using a new narrowband filter (NB704, lambda(c) = 7046 Angstrom and FWHM = 100 Angstrom) to detect LAEs at z = 4.79, i.e., LAEs lying closer to us by 39 h(70)(-1) Mpc on average than the z = 4.86 objects. We detect 51 LAEs at z = 4.79 +/- 0.04 down to NB704 = 25.7, and we find that their sky distribution is quite different from the z = 4.86 LAEs'. The clustering of z = 4.79 LAEs is very weak on any scale, and there is no large-scale high-contrast structure. The shape and the amplitude of the angular correlation fun tion are thus largely different between the two samples. The results demonstrate a large cosmic variance in the clustering properties of LAEs on scales of similar to50 h(70)(-1) Mpc.

GRB 030329 is the first Gamma-ray burst event for which a connection with a supernova (SN 2003dh) has been confirmed spectroscopically in its early phase. We present optical spectroscopy of this object 40 and 85 days after the burst (35 and 73 rest-frame days, respectively) obtained with the Subaru 8.2-m telescope. After subtracting the host galaxy template spectrum, the second-epoch spectrum shows nebular-phase emission lines emerging from the dominated photospheric-phase spectrum. The transition from the photospheric phase to the nebular phase has just started, or was slowly progressing at the time of our second-epoch observations. Our spectral analysis of the nebular-phase emission lines suggests that the explosion of the progenitor of the GRB 030329 was aspherical, and that the axis of an asphericity is well aligned to both the GRB relativistic jet and our line of sight. Although the decay index and the color evolution in the rest frame during our two epochs are very consistent with those of the Type Ic supernovae SN 1998bw and SN 1997ef, the nebular-phase lines emerged slightly earlier than in the case of these supernovae. These results infer that the most important factor that distinguishes SNe with GRB from SNe without GRB is the scale of the jet activity, or a viewing-angle effect, or both of them.

We carried out the deep follow-up observations of XRF011019 field using Suprime-Cam equipped with Subaru telescope at Mauna Kea. XRF011019 was localized by the Wide Field X-ray Monitor on board HETE-2 (Ricker et al. GCN1109). The events is so-called X-ray Flash (XRF). We had four epoch observations; twice on 2001 October 20, once on 2001 November 17, and finally in on 2002 January 12. The first two observations (on October 20) recorded two sources, which were absent in the third observation performed about a month later. One of the candidates is located near the X-ray position centroid, while the other is located outside the 95.5% error region of similar to30' radius. The former object could be the optical counterpart to the X-ray flash.

Based on our previous work about a co-evolution of massive black holes (MBH) and their host spheroids, we estimate the cosmic star formation history associated with AGN accretion by ROSAT X-ray All sky surveys. We show: 1) the total amount of star formation associated with MBH growth is at least half of the net star formation at high redshift, which probably totally missed by the current UV/optical deep surveys; 2) the FIR emission from the dust heated by star formation on-going during the MBH growth could be a significant energy source for SCUBA populations; 3)the peak redshift of the massive spheroid formation in this case is around 1.5, not necessary to be at much higher redshift.

Results of optical identification of the ASCA Lynx Deep Survey are presented. Six X-ray sources are detected in the 2-7 keV band using the Solid-State Imaging Spectrometer in a similar to20' x 20' field of view with fluxes larger than similar to4 x 10(-14) ergs s(-1) cm(-2) in the band. Follow-up optical spectroscopic observations were made, and five out of six sources are identified with active galactic nuclei/quasi-stellar objects (AGNs/QSOs) at redshifts of 0.5-1.3. We also identify two more additional X-ray sources detected in a soft X-ray band with AGNs/QSOs. We find that three QSOs identified are located at z similar to 1.3. Two rich clusters and several groups of galaxies are also placed at the same redshift in the surveyed field, and projected separations between the QSOs and the clusters are 3-8 Mpc at the redshift.

Spectroscopic and spectropolarimetric observations of SN 2003dh/GRB 030329 obtained in 2003 May using the Subaru 8.2 m Telescope are presented. The properties of the supernova (SN) are investigated through a comparison with spectra of the Type Ic hypernovae SN 1997ef and SN 1998bw (hypernovae being a tentatively defined class of SNe with very broad absorption features: these features suggest a large velocity of the ejected material and possibly a large explosion kinetic energy). Comparison with spectra of other hypernovae shows that the spectrum of SN 2003dh obtained on 2003 May 8 and 9, i.e., 34-35 rest-frame days after the gamma-ray burst (GRB; for z = 0.1685), are similar to those of SN 1997ef obtained similar to34-42 days after the fiducial time of explosion of that SN. The match with SN 1998bw spectra is not as good (at rest 7300-8000 Angstrom), but again spectra obtained similar to33-43 days after GRB 980425 are preferred. This indicates that the SN may have intermediate properties between SNe 1997ef and 1998bw. On the basis of the analogy with the other hypernovae, the time of explosion of SN 2003dh is then constrained to be between -8 and +2 days of the GRB. The Si and O P Cygni lines of SN 2003dh seem comparable to those of SN 1997ef, which suggests that the ejected mass in SN 2003dh may match that in SN 1997ef. Polarization was marginally detected at optical wavelengths. This is consistent with measurements of the late afterglow, implying that it originated mostly in the interstellar medium of the host galaxy.

The tight correlation between the masses of central black holes and their host spheroids in nearby galaxies and active galactic nuclei (AGNs) suggests that black hole growth is closely related to their spheroid formation. Based on our previous work regarding such a joint evolutionary scheme and the consequential black hole-to-bulge mass correlation, we use the X-ray luminosity function of AGN and the cosmological evolution rate, which are from ROSAT X-ray surveys, to estimate the cosmic star formation history associated with the black hole growth. By the basic assumption that the major black hole growth occurs during the luminous AGN phase, the luminosity function of AGNs as a function of redshift traces not only the accretion history of the black holes but also the cosmic star formation history of the spheroids. Although the space density of the especially luminous quasars is very low, we show that the total amount of star formation associated with the massive black hole growth is almost the same as that of Lyman break galaxies detected by the current optical deep surveys. We thus argue that the optical deep surveys may miss about half of the net star formation in our universe. This is probably due in part to significant dust extinction, as well as the small field of view of previous optical surveys, which cannot sample such rare events with relatively short timescale. However, the far-infrared emission from the dust heated by ongoing star formation during the black hole growth could sufficiently account for the observed SCUBA number counts and would be the probable dominating energy source of the SCUBA population.

We performed a deep optical imaging survey using a narrow-band filter (NB921) centered at lambda = 9196 (A) over circle together with i' and z' broadband filters covering an 814arcmin(2) area of the Subaru Deep Field. We obtained a sample of 73 strong NB 921 -excess objects based on the following two color criteria: z' - NB 921 > 1 and i' - z' > 1.3. We then obtained optical spectroscopy of nine objects in our NB 92 1 -excess sample, and identified at least two Ly a emitters at z = 6.541 +/- 0.002 and z = 6.578 +/- 0.002, each of which shows the characteristic sharp cutoff together with continuum depression at wavelengths shortward of the line peak. The latter object is more distant than HCM-6A at z = 6.56, which is the most distant known object that has been found so far. These new data allow us to estimate the first meaningful lower limit of the star-formation rate density beyond redshift 6; rho(SFR) similar to 5.2 x 10(-4) M-circle dot yr(-1) Mpc(-3). Since it is expected that the actual density is several times higher than this value, our new observation reveals that a moderately high level of star formation activity already occurred at z similar to 6.6.

We report the discovery of a large-scale structure of Lyalpha emitters (LAEs) at z = 4.86 based on wide-field imaging with the prime-focus camera (Suprime-Cam) on the Subaru Telescope. We observed a 25' x 45' area of the Subaru Deep Field in a narrow band (NB711, lambda(c) = Angstrom and FWHM = 73 Angstrom) together with R and i'. We isolate from these data 43 LAE candidates down to NB711 = 25.5 mag using color criteria. Follow-up spectroscopy of five candidates suggests the contamination by low-z objects to be similar to20%. We find that the LAE candidates are clustered in an elongated region on the sky of 20 Mpc in width and 50 Mpc in length at z = 4.86, which is comparable in size to present-day large-scale structures (we adopt H-0 = 70 km s(-1) Mpc(-1), Omega(0) = 0.3, and lambda(0) = 0.7). This elongated region includes a circular region of 12 Mpc radius of higher surface overdensity (delta(Sigma) = 2), which may be the progenitor of a cluster of galaxies. Assuming this circular region to be a sphere with a spatial overdensity of 2, we compare our observation with predictions by cold dark matter models. We find that an Omega(0) = 0.3 flat model with sigma(8) = 0.9 predicts the number of such spheres consistent with the observed number (one sphere in our survey volume) if the bias parameter of LAEs is b similar or equal to 6. This value suggests that the typical mass of dark halos hosting LAEs at z similar or equal to 5 is of the order of 10(12) M-circle dot. Such a large mass poses an interesting question about the nature of LAEs.

We present a high-resolution spectrum of the quasar HS 1603+ 3820 (z(em) = 2.542), observed with the High Dispersion Spectrograph on the Subaru Telescope. This quasar, first discovered in the Hamburg/CfA Quasar Survey, has 11 C IV lines at 1.96 < z(abs) < 2.55. Our spectrum covers eight of the 11 C IV lines at z(abs) > 2.29 and resolves some of them into multiple narrow components with b < 25 km s(-1) because of the high spectral resolution R = 45,000, while other lines show broad profiles (b > 65 km s(-1)). We use three properties of C IV lines, specifically, time variability, covering factor, and absorption-line profile, to classify them into quasar intrinsic absorption lines ( QIALs) and spatially intervening absorption lines (SIALs). The C IV lines at 2.42 < z(abs) < 2.45 are classified as QIALs in spite of their large velocity shifts from the quasar. Perhaps they are produced by gas clouds ejected from the quasar with velocity v(ej) = 8000-10,000 km s(-1). On the other hand, three C IV lines at 2.48 < z(abs) < 2.55 are classified as SIALs, which suggests there exist intervening absorbers near the quasar. We, however, cannot rule out QIALs for the two lines at z(abs) similar to 2.54 and 2.55, because their velocity shifts, 430 km s(-1) blueward and 950 km s(-1) redward of the quasar, are very small. The C IV line at z(abs) similar to 2.48 consists of many narrow components and also has corresponding low-ionization metal lines (Al II Si II and Fe II). The velocity distribution of these low-ionization ions is concentrated at the center of the system compared with that of the high-ionization C IV ion. Therefore we ascribe this system of absorption lines to an intervening galaxy.

We present the results of a survey for emission-line objects, based on optical intermediate-band (lambda(c) = 5736 Angstrom and Deltalambda = 280 Angstrom) and broadband (B, V, R, and i') observations of the Subaru/XMM-Newton Deep Field with the 8.2 m Subaru telescope and the Subaru Prime Focus Camera (Suprime-Cam). All the data were obtained during the guaranteed time observations of the Suprime-Cam instrument. The intermediate-band image covered a sky area of 10.'62 x 12.'40 approximate to132 arcmin(2) in the Subaru/XMM-Newton Deep Field (Ouchi et al.). Using this image, we found 23 emission-line sources whose observed emission-line equivalent widths are greater than 250 Angstrom. Their optical multicolor properties indicate that six emission-line sources are Lyalpha emitters at z approximate to 3.7 (Deltaz approximate to 0.22). They are either intense starburst galaxies or active galactic nuclei like quasars at z approximate to 3.7. Two more emission-line sources may also be Lyalpha emitters at z approximate to 3.7, although their multicolor properties are marginal. Among the remaining 15 emission-line objects, eight objects appear to be strong emission-line galaxies at lower redshift; e. g., [OII] lambda3727 emitters at z approximate to 0.54, Hbeta at z approximate to 0.18, or [O III] lambda5007 emitters at z approximate to 0.15. The remaining seven objects are unclassified because they are too faint to be detected in broadband images. We discuss the observational properties of these strong emission-line sources. In particular, our data allow us to estimate the star formation density at z approximate to 3.7 for the first time.

We report the first measurement of genus curves for the two-dimensional mass map in the neighborhood of the rich X-ray-luminous galaxy cluster MS 1054-03 at z=0.83, reconstructed from weak lensing data obtained by Suprime-Cam on the prime focus of the 8.2 m Subaru Telescope. We find that the genus curve measured in the whole survey field deviates from that expected from a random Gaussian field. We show that this non-Gaussianity is induced by the rich cluster in this region and that the genus curve for the region without the cluster is consistent with the prediction for a random Gaussian field. The results demonstrate the feasibility of the genus statistics to examine the non-Gaussianity due to the large-scale structures and to probe the statistical properties of the large-scale clustering.

Based on our previous work about a joint evolution and the consequential black hole to bulge mass correlation, we use the observed X-ray luminosity function of AGNs and their evolution to estimate the star formation history which is associated with the black hole growth. We show that the total amount of star formation associated with the massive black hole growth is almost the same as that detected by the current optical deep surveys. Meanwhile, the far infrared emission from the dust heated by star formation on-going during the black hole growth could sufficiently account for the observed SCUBA counts, and would be the good candidates of the SCUBA population.

We conducted deep NIR and optical imaging observations in general fields as well as the fields of cluster of galaxies and candidates at z > 1. In the observed rich cluster environment, massive galaxies have been well developed by z = 1.2 - 1.3. However, in a general field, HDF-N, we see conspicuous and sudden decrease of comoving number density of early-type galaxies above z = 1. There are few galaxies as massive as present-day L* galaxies at z=2-4 in HDF-N. Their rest-frame optical light is dominated by very young stellar population and their morphology also does not show any clear sequence. Thus formation/evolution of galaxies seems to strongly depend on their density environment and in general fields massive galaxies which form present-day Hubble sequence might have been formed between 1 < z < 2 while early type galaxies in clusters formed earlier epoch.

We present the results of the deep NIR imaging observations using the Subaru telescope. At the Hubble Deep Field North, we obtained the new and deepest K'-band image (10 hours) to study the rest-frame optical morphology of galaxies at z> 3 and the stellar mass distribution of galaxies at 2 < z < 4.5. We also study the rest-frame optical properties of the 'building blocks' in the field of 53W002 and overall color distribution there. We then combined these data to compare the color and magnitude distribution in these two fields. The opt-NIR color-magnitude distributions in the two fields looks very similar and we report the conspicuous color change below K-AB = 22 and discuss the cause of the feature.

We present spectropolarimetry of the Type Ic supernova SN 2002ap and give a preliminary analysis: the data were taken at two epochs, close to and 1 month later than the visual maximum (2002 February 8). In addition, we present June 9 spectropolarimetry without analysis. The data show the development of linear polarization. Distinct polarization profiles were seen only in the O I lambda7773 multiplet/Ca II IR triplet absorption trough at maximum light and in the O I lambda7773 multiplet and Ca II IR triplet absorption troughs a month later, with the latter showing a peak polarization as high as similar to2%. The intrinsic polarization shows three clear position angles: 80degrees for the February continuum, 120degrees for the February line feature, and 150degrees for the March data. We conclude that there are multiple asymmetric components in the ejecta. We suggest that the supernova has a bulk asymmetry with an axial ratio projected on the sky that is different from 1 by an order of 10%. Furthermore, we suggest very speculatively that a high-velocity ejecta component moving faster than similar to0.115c (e.g., a jet) contributes to polarization in the February epoch.

Hyper extremely red objects (HEROs) are objects that are very red in near-IR colors (J-K greater than or similar to 3). They are speculated to be intrinsically red galaxies at z greater than or similar to 2 or Lyman break galaxies at z > 10. We report the discovery of a HERO in the field that includes a known radio galaxy, 53W002, and a possible cluster of galaxies both at z = 2.39. The HERO, which we name HERO J171411.91+501541.8, or 53W002-HERO1 for brevity, is visible in the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer H-band data and deep K'-band data from the Subaru Telescope (K' similar or equal to 21.5 mag) but not visible in B-, V-, I-, and J-band images (J-K > 4.45, 2 sigma). Its spectral energy distribution is consistent with that of a dusty star- forming or old galaxy at z similar or equal to 2.4, which may suggest that 53W002-HERO1 is a member of the group of galaxies associated with 53W002. Alternatively, the HERO could be at z similar or equal to 12.5, if its red color is due to the redshifted Lyman break. If 53W002- HERO1 is an old galaxy at z similar to 2.4, the implied stellar age is similar to2- 3 Gyr, meaning that stars in the HERO formed at the reionization epoch of z greater than or similar to 10.

We present the first results of Chandra and optical follow-up observations of hard X-ray sources detected in the ASCA Medium Sensitivity Survey (AMSS). Optical identifications were made for five objects. Three of them show either weak or absent optical narrow emission lines, and are at low redshift <z> similar to 0.06. One of them is a broad line object at z = 0.910 and one is a z = 0.460 object with only narrow lines. All of the narrow-line objects show strong evidence of absorption in their X-ray spectra. Their line ratios are consistent with a Seyfert II/LINER identification, as are the line widths. The three low-redshift objects have the colors of normal galaxies, and apparently the light is dominated by stars. This could be due to extinction of the underlying nuclear continuum by the same matter that absorbs X-rays and/or due to dilution of the central source by starlight. These results suggest that X-ray sources that appear as "normal" galaxies in optical and near-IR bands significantly contribute to the hard X-ray background. This population of objects has a high space density, and probably dominates the entire population of active galaxies.

We have obtained a new high-resolution K'-band image of the central region of the rich X-ray cluster RX J0848.9+4452 at z = 1.26. We found that the brightest cluster galaxy (BCG) in the cluster is clearly separated into two distinct objects. Whereas the optical to near-infrared colors of the objects are consistent with the predictions of passive evolution models for galaxies formed at high redshift, the luminosities of the two galaxies are both considerably fainter than predicted by passive evolution of BCGs in low- and intermediate-redshift clusters. We argue that this is evidence of an ongoing merger of normal cluster elliptical galaxies to form the dominant galaxy in the core of RX J0848.9+4452. The two galaxies appear to point toward the nearby cluster ClG J0848+4453 and are aligned with the outer X-ray contour of their parent cluster, supporting a model of BCG formation by collimated infall along the surrounding large-scale structure.

We study properties of cluster galaxies around the radio galaxy 3C324 at z = 1.2 with BV RIK' multi-band imaging data. We apply a photometric-redshift technique to the objects in the 3C324 field, and identify plausible cluster members. With the data, we investigate properties of the cluster galaxies, such as the luminosity function, the color properties, and the blue fraction.

We discuss the properties of galaxies around the radio galaxy 3C 324 at z = 1.2 based on B VRI K' multi-band imaging data. We have applied a photometric-redshift technique to objects in the 3C 324 field, and identified 35 objects as plausible cluster members. We have found that red and luminous members are concentrated in a small region enclosed by a circle of 40" radius (0.33 Mpc at z = 1.2 for Omega(0) = 0.3, lambda(0) = 0.7, H-0 = 70 kms(-1) Mpc(-1) cosmology) from the 3C 324 galaxy. The 3C 324 cluster is probably much more compact in size compared with the local clusters. We constructed a V-band luminosity function of the cluster members and fitted a Schechter function, and found the characteristic magnitude to be K-AB'* = 20.2 +/- 0.6. This value is consistent with the extrapolation of the pure AB passive evolution seen for z < I clusters. We have identified eight bright galaxies which form a red color-magnitude sequence. The slope of the sequence is consistent with the passive evolution model down to K-AB' < 22; we also A found that there is no clear age variation in these bright red galaxies. However, seven out of these eight galaxies exhibit a significant excess in the rest UV light with respect to the passive evolution model. This may suggest that the massive early-type galaxies in this high-redshift cluster are still forming stars to some extent. We have confirmed a truncation of the color-magnitude sequence at K-AB' similar to 22; faint passively-evolving, galaxies may not yet be present in this cluster at z similar to 1.2. The overall color distribution of the cluster members, selected by the photometric redshift technique, is found to be very broad. We derived the fraction of blue galaxies in this cluster following a definition of Butcher and Oemler (1984, AAA 038.160.068), and obtained f(B) = 0.39 +/- 0.28, which is higher than that for z < 1 clusters. This indicates that the star-formation activity of this cluster is, on the average, higher than that of lower redshift counterparts.

We present the results of deep K'- and J-band imaging of the field of a proto-cluster region near the radio galaxy 53W002 at z = 2.390 with the Subaru Telescope. The data were analyzed together with deep optical and near-infrared (NIR) images taken with the Hubble Space Telescope to investigate the properties of ten optically compact emission-line galaxies and candidates. Excluding the three objects which may contain active galactic nuclei, many are faint or undetected at K' (lambda(rest) approximate to 6000Angstrom), and are therefore revealed to be intrinsically small starbursting objects. On the other hand, we detect few objects with colors and magnitudes expected for quiescent massive galaxies at z = 2.4 in the field.

Using the HST WFPC2/NICMOS archival data of the Hubble Deep Field North, we constructed a nearly complete sample of the M-V < -20 (similar to L* + 1) galaxies to z = 2, and investigate when the Hubble sequence appeared, namely, the evolution of the morphology, colors, and the comoving number density of the sample. Even if taking into account the uncertainty of the photometric redshift technique, the number density of relatively bright bulge-dominated galaxies in the HDF-N decreases significantly at z > 1, and their rcst-frame U - V color distribution is wide-spread over 0.5 < z < 2. On the other hand, while the number density of both disk-dominated and irregular galaxies does not show a significant change at 0.5 < z < 2, their distribution of the rest-frame U - V color alters at z similar to 1.5; there is no relatively red (rest U - V greater than or similar to 0.3) galaxies at z > 1.5, while a significant fraction of these red disk-dominated or irregular galaxies exist at z < 1.5. These results suggest that the significant evolution of the Hubble sequence, which is seen in the present Universe, occurs at 1 < z < 2.

We present low-resolution, near-IR JHK spectra of the weak z = 2.39 radio galaxy 53W002, obtained with the OH-airglow Suppressor spectrograph (OHS) and Cooled Infrared Spectrograph and Camera for OHS (CISCO) on the Subaru Telescope. They cover rest-frame wavelengths of 3400-7200 Angstrom, and the emission lines of [O u] lambda 3727, H beta, [O III] lambda lambda 4959, 5007, H alpha, [N II] lambda lambda 6548, 6583 and [S II] lambda lambda 6716, 6731 were detected. Using the H alpha /H beta line ratio, we find an extinction of E(B - V) = 0.14. The emission-line ratios are reproduced by a cloud of electron density n(e) = 1 x 10(3-4) cm(-3) with solar metallicity, ionized by an alpha = -0.7 power-law continuum with ionizing parameter U = 1 x 10(-3). In addition to these emission lines, we make the first spectroscopic confirmation of the Balmer discontinuity in a high-z radio galaxy. Together with rest-frame UV photometry from the literature, we show that at least 1/3 of the present stellar mass was formed in the current starburst. The stellar mass was estimated to be (1-1.4) x 10(11) M-circle dot by one-component model fitting, which is smaller than that of typical z similar to 1 B2/6C radio galaxies. We suggest that 53W002 is currently assembling a large part of its stellar mass through merger events with the surrounding sub-galactic clumps, some of which can be identified with the Let emitters detected in narrow-band imaging. After a few such events over the next few Gyr, 53W002 will evolve into a massive elliptical galaxy.

We present new optical data on the cluster AX J2019+1127 identified by the X-ray satellite ASCA at z similar to 1 (Hattori et al. 1997). The data suggest the presence of a high-redshift cluster of galaxies responsible for the large separation triple quasar MG 2016+112. Our deep photometry reveals an excess of z similar to 1 galaxy candidates, as already suspected by Benitez et al. (1999). Our spectroscopic survey of 44 objects in the field shows an excess of 6 red galaxies securely identified at z similar to 1, with a mean redshift of z = 1.005 +/- 0.002. We estimate a velocity dispersion of sigma = 771(-160)(+430) km s(-1) based on these 6 galaxies and a V-band mass-to-light ratio of 215(-77)(+308) h(50) (M/L-v)(circle dot). Our observations thus confirm the existence of a massive structure acting as the lens, which explains the unusual configuration of the triple quasar. Hence, there is no need to invoke the existence of a "dark cluster" to understand this lens system.

We report on a wide-area (48' x 9') imaging survey of faint galaxies in the R and I bands toward the 1338 + 27 field where an unusual concentration of five QSOs at z similar to 1.1, embedded in a larger scale clustering of 23 QSOs, is known to exist. Using a quite homogeneous galaxy catalog with a detection completeness limit of I similar to 23.5, we detect a significant clustering signature of faint red galaxies with I > 21 and R-I > 1.2 over a scale extending to similar to 20 h(50)(-1) Mpc. Close examination of the color-magnitude diagram, the luminosity function, and the angular correlation function indeed suggests that those galaxies are located at z similar to 1.1 and trace the underlying large-scale structure at that epoch, together with the group of five QSOs. Since the whole extent of the cluster of 23 QSOs (similar to 70 h(50)(-1) Mpc) is roughly similar to the local "Great Wall," the area may contain a high-redshift counterpart of superclusters in the local universe.

We present new high signal-to-noise ratio spectra of the components B and C of the gravitational lensing system MG 2016+112. We show that image C displays strong emission lines of Ly alpha, NV, CIV, Hell, and CIII] redshifted to z = 3.27, similar to images A and B. We examine the emission-line flux ratios in order to put constraints on the lens models as well as to investigate the intrinsic nature of MG 2016+112. The observed line ratios of B and C are consistent with those expected in the simple photo-ionization models for narrow-line region of active galactic nuclei (AGN) except for the enhanced NV lines. The line ratios difference of components B and C can be interpreted as a difference in ionization parameters. This result is consistent with lens model prediction that C is a fold image of a slightly outer part of the nucleus. MG 2016+112 is known to be very unique among the high-redshift AGN; it is neither an ordinary broad-line quasar nor a powerful radio galaxy as indicated by the width and flux ratio of the emission lines. Together with other observed properties discussed in Literature, we argue that MG 2016+112 may be an obscured luminous radio-quiet quasar.

We present low-resolution, near-IR JHK spectra of the weak z = 2.39 radio galaxy 53W002 and its companion objects #18 and #19, obtained with OHS/CISCO on the Subaru Telescope. They cover rest-frame wavelengths of 3400-7200 Angstrom, and many rest-optical emission lines are detected, Contributions to the broad-band flux from these emission lines are found to be very large, up to 40% in the H and K'-bands and 30% in the J-band.

We present the result of a wide-area (48' x 9') imaging survey of faint galaxies toward the 1338+27 field where an unusual concentration of five QSOs at z similar to 1.1 is known to exist. We have detected a significant clustering signature of faint red galaxies with I > 21 and R - I > 1.2 over a scale extending to - 20h(50)(-1) Mpc at z - 1.1. The R - I colors of these galaxies and the angular correlation function analysis strongly suggests that these galaxies are indeed at the redshift of the group of five QSOs. Our new K'-band images for three selected density peaks also supported the idea. Since this group of five QSOs are indeed a part of much larger (- 70h(50)(-1) Mpc) clustering of 23 QSOs discovered by Crampton et al. (1988), the whole size of the detected structure may be as large as the local "Great Wall" structure.

We report the current status of the ASCA Medium Sensitivity Survey (AMSS; or the GIS catalog project). The latest results from the optical identification program for a hard-band selected sample are presented.