arXiv subjects

T. Takata

Publications and source records attributed to T. Takata.

At least 19 recordsLinked to original sources

arXiv2018

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). IV. Discovery of 41 Quasars and Luminous Galaxies at 5.7 < z < 6.9

We report discovery of 41 new high-z quasars and luminous galaxies, which were spectroscopically identified at 5.7 < z < 6.9. This is the fourth in a series of papers from the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, based on the deep multi-band imaging data collected by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. We selected the photometric candidates by a Bayesian probabilistic algorithm, and then carried out follow-up spectroscopy with the Gran Telescopio Canarias and the Subaru Telescope. Combined with the sample presented in the previous papers, we have now spectroscopically identified 137 extremely-red HSC sources over about 650 deg2, which include 64 high-z quasars, 24 high-z luminous galaxies, 6 [O III] emitters at z ~ 0.8, and 43 Galactic cool dwarfs (low-mass stars and brown dwarfs). The new quasars span the luminosity range from M1450 ~ -26 to -22 mag, and continue to populate a few magnitude lower luminosities than have been probed by previous wide-field surveys. In a companion paper, we derive the quasar luminosity function at z ~ 6 over an unprecedentedly wide range of M1450 ~ -28 to -21 mag, exploiting the SHELLQs and other survey outcomes.

astro-ph.GA↗

arXiv2014

AzTEC/ASTE 1.1 mm survey of SSA22: Counterpart identification and photometric redshift survey of submillimeter galaxies

We present the results from a 1.1 mm imaging survey of the SSA22 field, known for having an overdensity of z=3.1 Lyman-alpha emitting galaxies (LAEs), taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment (ASTE). We imaged a 950 arcmin$^2$ field down to a 1 sigma sensitivity of 0.7-1.3 mJy/beam to find 125 submillimeter galaxies (SMGs) with a signal to noise ratio >= 3.5. Counterpart identification using radio and near/mid-infrared data was performed and one or more counterpart candidates were found for 59 SMGs. Photometric redshifts based on optical to near-infrared images were evaluated for 45 SMGs of these SMGs with Spitzer/IRAC data, and the median value is found to be z=2.4. By combining these estimation with estimates from the literature we determined that 10 SMGs might lie within the large-scale structure at z=3.1. The two-point angular cross-correlation function between LAEs and SMGs indicates that the positions of the SMGs are correlated with the z=3.1 protocluster. These results suggest that the SMGs were formed and evolved selectively in the high dense environment of the high redshift universe. This picture is consistent with the predictions of the standard model of hierarchical structure formation.

astro-ph.CO↗

arXiv2011

Detection of an ultra-bright submillimeter galaxy in the Subaru/XMM-Newton Deep Field using AzTEC/ASTE

We report the detection of an extremely bright ($\sim$37 mJy at 1100 $μ$m and $\sim$91 mJy at 880 $μ$m) submillimeter galaxy (SMG), AzTEC-ASTE-SXDF1100.001 (hereafter referred to as SXDF1100.001 or Orochi), discovered in 1100 $μ$m observations of the Subaru/XMM-Newton Deep Field using AzTEC on ASTE. Subsequent CARMA 1300 $μ$m and SMA 880 $μ$m observations successfully pinpoint the location of Orochi and suggest that it has two components, one extended (FWHM of $\sim$ 4$^{\prime\prime}$) and one compact (unresolved). Z-Spec on CSO has also been used to obtain a wide band spectrum from 190 to 308 GHz, although no significant emission/absorption lines are found. The derived upper limit to the line-to-continuum flux ratio is 0.1--0.3 (2 $σ$) across the Z-Spec band. Based on the analysis of the derived spectral energy distribution from optical to radio wavelengths of possible counterparts near the SMA/CARMA peak position, we suggest that Orochi is a lensed, optically dark SMG lying at $z \sim 3.4$ behind a foreground, optically visible (but red) galaxy at $z \sim 1.4$. The deduced apparent (i.e., no correction for magnification) infrared luminosity ($L_{\rm IR}$) and star formation rate (SFR) are $6 \times 10^{13}$ $L_{\odot}$ and 11000 $M_{\odot}$ yr$^{-1}$, respectively, assuming that the $L_{\rm IR}$ is dominated by star formation. These values suggest that Orochi will consume its gas reservoir within a short time scale ($3 \times 10^{7}$ yr), which is indeed comparable to those in extreme starbursts like the centres of local ULIRGs.

astro-ph.CO↗

arXiv2010

Submillimeter Array Identification of the Millimeter-Selected Galaxy SSA22-AzTEC1: A Protoquasar in a Protocluster?

We present results from Submillimeter Array (SMA) 860-micron sub-arcsec astrometry and multiwavelength observations of the brightest millimeter (S_1.1mm = 8.4 mJy) source, SSA22-AzTEC1, found near the core of the SSA22 protocluster that is traced by Lyαemitting galaxies at z = 3.09. We identify a 860-micron counterpart with a flux density of S_860um = 12.2 +/- 2.3 mJy and absolute positional accuracy that is better than 0.3". At the SMA position, we find radio to mid-infrared counterparts, whilst no object is found in Subaru optical and near-infrared deep images at wavelengths \le 1 micron (J > 25.4 in AB, 2σ). The photometric redshift estimate, using flux densities at \ge 24 microns, indicates z_phot = 3.19^{+0.26}_{-0.35}, consistent with the protocluster redshift. We then model the near-to-mid-infrared spectral energy distribution (SED) of SSA22-AzTEC1, and find that the SED modeling requires a large extinction (A_V \approx 3.4 mag) of starlight from a stellar component with M_star ~ 10^{10.9} M_sun, assuming z = 3.1. Additionally, we find a significant X-ray counterpart with a very hard spectrum (Gamma_eff = -0.34 ^{+0.57}_{-0.61}), strongly suggesting that SSA22-AzTEC1 harbors a luminous AGN (L_X ~ 3*10^{44} ergs s^{-1}) behind a large hydrogen column (N_H ~ 10^{24} cm^{-2}). The AGN, however, is responsible for only ~10% of the bolometric luminosity of the host galaxy, and therefore the star-formation activity likely dominates the submillimeter emission. It is possible that SSA22-AzTEC1 is the first example of a protoquasar growing at the bottom of the gravitational potential underlying the SSA22 protocluster.

astro-ph.CO↗

arXiv2010

"Dark" GRB 080325 in a Dusty Massive Galaxy at z ~ 2

We present optical and near infrared observations of GRB 080325 classified as a "Dark GRB". Near-infrared observations with Subaru/MOIRCS provided a clear detection of afterglow in Ks band, although no optical counterpart was reported. The flux ratio of rest-wavelength optical to X-ray bands of the afterglow indicates that the dust extinction along the line of sight to the afterglow is Av = 2.7 - 10 mag. This large extinction is probably the major reason for optical faintness of GRB 080325. The J - Ks color of the host galaxy, (J - Ks = 1.3 in AB magnitude), is significantly redder than those for typical GRB hosts previously identified. In addition to J and Ks bands, optical images in B, Rc, i', and z' bands with Subaru/Suprime-Cam were obtained at about one year after the burst, and a photometric redshift of the host is estimated to be z_{photo} = 1.9. The host luminosity is comparable to L^{*} at z \sim 2 in contrast to the sub-L^{*} property of typical GRB hosts at lower redshifts. The best-fit stellar population synthesis model for the host shows that a large dust extinction (Av = 0.8 mag) attributes to the red nature of the host and that the host galaxy is massive (M_{*} = 7.0 \times 10^{10} Msun) which is one of the most massive GRB hosts previously identified. By assuming that the mass-metallicity relation for star-forming galaxies at z \sim 2 is applicable for the GRB host, this large stellar mass suggests the high metallicity environment around GRB 080325, consistent with inferred large extinction.

astro-ph.GA↗

arXiv2008

The SCUBA HAlf Degree Extragalactic Survey (SHADES) - VII. Optical/IR photometry and stellar masses of sub-millimeter galaxies

We present estimates of the photometric redshifts, stellar masses and star formation histories of sources in the SCUBA HAlf Degree Extragalactic Survey (SHADES). This paper describes the 60 SCUBA sources detected in the Lockman Hole covering an area of ~320 square arcmin. Using photometry spanning the B band to 8um, we find that the average SCUBA source forms a significant fraction of its stars in an early period of star formation and that most of the remainder forms in a shorter more intense burst around the redshift it is observed. This trend does not vary significantly with source redshift but the exact ratio of early to late mass is quite sensitive to the way extinction is treated in the modelling. However, the sources show a clear increase in stellar mass with redshift, consistent with downsizing. In terms of SED types, only two out of the 51 sources we have obtained photometric redshifts for are best fit by a quasar-like spectral energy distribution, with approximately 80 per cent of the sources being best fit with late-type spectra (Sc, Im and starburst). By including photometry at 850um, we conclude that the average SCUBA source is forming stars at a rate somewhere between 6 and 30 times the rate implied from the rest-frame optical in a dust obscured burst and that this burst creates 15-65 per cent of the total stellar mass. Using a simplistic calculation, we estimate from the average star formation history that between one in five and one in 15 bright (L_* +2 mag < L_optical < L_* -1 mag) galaxies in the field over the interval 0 < z < 3 will at some point in their lifetime experience a similar energetic dusty burst of star formation. Finally, we compute the evolution of the star formation rate density and find it peaks around z=2.

astro-ph↗

arXiv2008

The Subaru/XMM-Newton Deep Survey (SXDS) - II. Optical Imaging and Photometric Catalogs

We present multi-waveband optical imaging data obtained from observations of the Subaru/XMM-Newton Deep Survey (SXDS). The survey field, centered at R.A.=02:18:00, decl.=-05:00:00, has been the focus of a wide range of multi-wavelength observing programs spanning from X-ray to radio wavelengths. A large part of the optical imaging observations are carried out with Suprime-Cam on Subaru Telescope at Mauna Kea in the course of Subaru Telescope Observatory Projects. This paper describes our optical observations, data reduction and analysis procedures employed, and the characteristics of the data products. A total area of 1.22 sqdeg is covered in five contiguous sub-fields, each of which corresponds to a single Suprime-Cam field of view (34'x27'), in five broad-band filters B, V, Rc, i', z' to the depths of B=28.4, V=27.8, Rc=27.7, i'=27.7 and z'=26.6 (AB, 3-sigma, 2-arcsec aperture). The data are reduced and compiled into five multi-waveband photometric catalogs, separately for each Suprime-Cam pointing. The i'-band catalogs contain about 900,000 objects, making the SXDS catalogs one of the largest multi-waveband catalogs in corresponding depth and area coverage. The SXDS catalogs can be used for an extensive range of astronomical applications such as the number density of the Galactic halo stars to the large scale structures at the distant universe. The number counts of galaxies are derived and compared with those of existing deep extragalactic surveys. The optical data, the source catalogs, and configuration files used to create the catalogs are publicly available via the SXDS web page (http://www.naoj.org/Science/SubaruProject/SXDS/index.html)

astro-ph↗

arXiv2007

The SCUBA HAlf Degree Extragalactic Survey (SHADES) -- V. Submillimetre properties of near-infrared--selected galaxies in the Subaru/XMM--Newton deep field

We have studied the submillimetre (submm) properties of the following classes of near-infrared (NIR)-selected massive galaxies at high redshifts: BzK-selected star-forming galaxies (BzKs); distant red galaxies (DRGs); and extremely red objects (EROs). We used the SCUBA HAlf Degree Extragalactic Survey (SHADES), the largest uniform submm survey to date. Partial overlap of SIRIUS/NIR images and SHADES in SXDF has allowed us to identify 4 submm-bright NIR-selected galaxies, which are detected in the mid-infrared, 24 micron, and the radio, 1.4 GHz. We find that all of our submm-bright NIR-selected galaxies satisfy the BzK selection criteria, except for one galaxy whose B-z and z-K colours are however close to the BzK colour boundary. Two of the submm-bright NIR-selected galaxies satisfy all of the selection criteria we considered, i.e. they belong to the BzK-DRG-ERO overlapping population, or `extremely red' BzKs. Although these extremely red BzKs are rare (0.25 arcmin^{-2}), up to 20 % of this population could be submm galaxies. This fraction is significantly higher than that found for other galaxy populations studied here. Via a stacking analysis, we have detected the 850 micron flux of submm-faint BzKs and EROs in our SCUBA maps. While the contribution of z~2 BzKs to the submm background is about 10--15 % and similar to that from EROs typically at z~1, BzKs have a higher fraction (~30 %) of submm flux in resolved sources compared with EROs and submm sources as a whole. From the SED fitting analysis for both submm-bright and submm-faint BzKs, we found no clear signature that submm-bright BzKs are experiencing a specifically luminous evolutionary phase, compared with submm-faint BzKs. An alternative explanation might be that submm-bright BzKs are more massive than submm-faint ones.

astro-ph↗

arXiv2005

Afterglow spectrum of a gamma-ray burst with the highest known redshift z=6.295

Gamma-ray bursts (GRBs) and their afterglows have been proposed as an excellent probe to study the evolution of cosmic star formation, the reionization of the intergalactic medium, and the metal enrichment history of the universe, since the prompt gamma-ray emission of GRBs should be detectable out to distances z>10. Hitherto, the highest measured redshift for a GRB has been z=4.50. Here we report the optical spectrum of the afterglow of GRB 050904 obtained 3.4 days after the burst. The spectrum shows a clear continuum at the long wavelength end of the spectrum with a sharp cutoff at around 9000 A due to Ly alpha absorption at a redshift of 6.3 with a damping wing. Little flux is present in the waveband shortward of the Ly alpha break. A system of absorption lines of heavy elements at redshift z=6.295 +- 0.002 were also detected, yielding a precise measurement of the largest known redshift of a GRB. Analysis of the Si II fine structure lines suggest a dense metal-enriched environment around the GRB progenitor, providing unique information on the properties of the gas in a galaxy when the universe was younger than one billion years.

astro-ph↗

arXiv2005

XMM-Newton 13H Deep field - I. X-ray sources

We present the results of a deep X-ray survey conducted with XMM-Newton, centred on the UK ROSAT 13H deep field area. This region covers 0.18 deg^2 and is the first of two areas covered with XMM-Newton as part of an extensive multi-wavelength survey designed to study the nature and evolution of the faint X-ray source population. We have produced detailed Monte-Carlo simulations to obtain a quantitative characterisation of the source detection procedure and to assess the reliability of the resultant sourcelist. We use the simulations to establish a likelihood threshold above which we expect less than 7 (3%) of our sources to be spurious. We present the final catalogue of 225 sources. Within the central 9 arcmin, 68 per cent of source positions are accurate to 2 arcsec, making optical follow-up relatively straightforward. We construct the N(>S) relation in four energy bands: 0.2-0.5 keV, 0.5-2 keV, 2-5 keV and 5-10 keV. In all but our highest energy band we find that the source counts can be represented by a double powerlaw with a bright end slope consistent with the Euclidean case and a break around 10^-14 cgs. Below this flux the counts exhibit a flattening. Our source counts reach densities of 700, 1300, 900 and 300 deg^-2 at fluxes of 4.1x10^-16, 4.5x10^-16, 1.1x10^-15 and 5.3x10^-15 cgs in the 0.2-0.5, 0.5-2, 2-5 and 5-10 keV energy bands respectively. We have compared our source counts with those in the two Chandra deep fields and Lockman hole and find our source counts to be amongst the highest of these fields in all energy bands. We resolve >51% (>50%) of the X-ray background emission in the 1-2 keV (2-5 keV) energy bands.

astro-ph↗

arXiv2004

The Discovery of Primeval Large-Scale Structures with Forming Clusters at Redshift 6

We report the discovery of primeval large-scale structures (LSSs) including two proto-clusters in a forming phase at z=5.7. We carried out extensive deep narrow-band imaging in the 1 deg^2 sky of the Subaru/XMM-Newton Deep Field, and obtained a cosmic map of 515 Ly alpha emitters (LAEs) in a volume with a transverse dimension of 180 Mpc x 180 Mpc and a depth of ~40 Mpc in comoving units. This cosmic map shows filamentary LSSs, including 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, ~80, of LAEs. These clumps would be clusters in a formation phase involving a burst of galaxy formation.

astro-ph↗

arXiv2004

Nature of a Strongly-Lensed Submillimeter Galaxy SMM J14011+0252

We have carried out near-infrared JHK spectroscopy of a gravitationally lensed submillimeter galaxy SMM J14011+0252 at z=2.565, using OHS and CISCO on the Subaru telescope. This object consists of two optical components, J1 and J2, which are lensed by the cluster Abell 1835. J1 suffers additional strong lensing by a foreground galaxy at z=0.25 in the cluster. The rest-optical H-alpha, H-beta, and [O II]3727 lines are detected in both J1 and J2, and [N II]6548,6583 lines are also detected in J1. A diagnosis of emission-line ratios shows that the excitation source of J1 is stellar origin, consistent with previous X-ray observations. The continua of J1 and J2 show breaks at rest 4000A, indicating relatively young age. Combined with optical photometry, we have carried out model spectrum fitting of J2 and find that it is a very young (~50 Myr) galaxy of rather small mass (~10e8 M_sol) which suffers some amount of dust extinction. A new gravitational lensing model is constructed to assess both magnification factor and contamination from the lensing galaxy of the component J1, using HST-F702W image. We have found that J1 suffers strong lensing with magnification of ~30, and its stellar mass is estimated to be < 10e9 M_sol. These results suggest that SMM J14011+0252 is a major merger system at high redshift that undergoes intense star formation, but not a formation site of a giant elliptical. Still having plenty of gas, it will transform most of the gas into stars and will evolve into a galaxy of < 10e10 M_sol. Therefore, this system is possibly an ancestor of a less massive galaxy such as a mid-sized elliptical or a spiral at the present.

astro-ph↗

arXiv2004

Problems on invariants of knots and 3-manifolds

This is a list of open problems on invariants of knots and 3-manifolds with expositions of their history, background, significance, or importance. This list was made by editing open problems given in problem sessions in the workshop and seminars on `Invariants of Knots and 3-Manifolds' held at Kyoto in 2001.

math.GT↗

arXiv2003

On The Spectrum and Spectropolarimetry of Type Ic Hypernova SN 2003dh/GRB 030329

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 SN are investigated through a comparison with spectra of the Type Ic hypernovae SNe 1997ef and 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 GRB (for z=0.1685), are similar to those of SN 1997ef obtained ~34-42 days after the fiducial time of explosion of that SN. The match with SN 1998bw spectra is not as good (at rest 7300-8000 A, but again spectra obtained ~33-43 days after GRB 980425 are preferred. This indicates that the SN may have intermediate properties between SNe 1997ef and 1998bw. Based on 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 mostly originated in the interstellar medium of the host galaxy.

astro-ph↗

arXiv2003

On the Origin of Lyman-$α$ Blobs at High Redshift: Kinematic Evidence for a Hyperwind Galaxy at z = 3.1

We present deep optical spectroscopy of an extended Ly$α$ emission-line blob located in an over-dense region at redshift $z \approx 3.1$; `blob 1' of Steidel et al. (2000). The origin of such Ly$α$ blobs has been debated for some time; two of the most plausible models are (1) that it comes from a dust-enshrouded, extreme starburst galaxy with a large-scale galactic outflow (superwind/hyperwind) or (2) that it is the cooling radiation of proto-galaxies in dark matter halos. Examination of the kinematic properties of the Ly$α$ emission-line gas should allow us to determine its nature. With this motivation, we performed optical spectroscopy of `blob 1' using the Subaru Telescope, and found that its kinematic properties can be well explained in terms of superwind activity.

astro-ph↗

arXiv2003

A Vigorous Starburst in the SCUBA Galaxy N2 850.4

We present optical and near-IR spectroscopy of a z=2.38 hyperluminous IR galaxy, covering the restframe wavelength range from 1000-5000A. It appears to comprise two components separated by less than 1" on the sky (<8kpc); one component (B) is blue, the other (P) is red in restframe UV-optical colours. The combined system has an optical luminosity of ~8L* and its restframe optical spectrum is characteristic of a Seyfert AGN. However, its restframe UV spectrum exhibits striking features associated with young stars, including P-Cygni lines from stellar winds and blue-shifted interstellar absorption lines indicative of a galactic outflow. Redshifts are derived from stellar photospheric lines in the UV and from narrow emission lines in the restframe optical, and these are compared to that measured for the molecular gas recently detected with the IRAM interferometer. The offsets indicate that the far-IR emission is most likely associated with the near-IR source P, which hosts the Seyfert nucleus, while the UV-bright component B is blueshifted by 400km/s. This suggests that the two components are probably merging and the resulting gravitational interactions have triggered the hyperluminous activity. Modelling of the UV spectral features implies that the starburst within the UV component of this system has been going on for at least ~10Myrs. Assuming that the bolometrically-dominant obscured component has a similar lifetime, we estimate that it has so far formed a total stellar mass of ~10^11 Mo. If this star formation continues at its present level for substantially longer, or if this activity is repeated, then the present-day descendant of N2 850.4 will be a very luminous galaxy.

astro-ph↗

arXiv2003

A medium deep Chandra and Subaru survey of the 13hr XMM/ROSAT deep survey area

We present the results of a Chandra ACIS-I survey of a high latitude region at 13h +38 which was earlier observed with ROSAT (McHardy et al. 1998) and which has recently been observed by XMM-Newton for 200ksec. XMM-Newton will provide good quality X-ray spectra for over 200 sources with fluxes around the knee of the logN/logS, which are responsible for the bulk of the X-ray background (XRB). The main aim of the Chandra observations is to provide arcsecond, or better, positions, and hence reliable identifications, for the XMM-Newton sources. The ACIS-I observations were arranged in a mosaic of four 30ksec pointings, covering almost all of the 15' radius XMM-Newton/ROSAT field. We detect 214 Chandra sources above 5 sigma significance, to a limiting flux of \~1.3e-15 erg/cm2/s (0.5-7 keV). Optical counterparts are derived from a Subaru SuprimeCam image reaching to R~27. The very large majority of the Chandra sources have an optical counterpart, with the distribution peaking at 23<R<24, although 14 have no counterpart to R=27. The fraction of X-ray sources with no identification brighter than R=27 is similar to that found in deeper Chandra surveys. The majority of the identifications are with galaxies. As found in other Chandra surveys, there is a very wide range of optical magnitude for given X-ray flux, implying a range of emission mechanisms, and many sources have high L_X/L_opt ratios, implying absorption at moderate redshift. Comparison with the earlier ROSAT survey shows that the accuracy of the ROSAT positions agrees very well with the predictions from simulations in McHardy et al. (1998) and that the large majority of the identifications were correct (abridged).

astro-ph↗

arXiv2003

Reshetikhin-Turaev invariants of Seifert 3-manifolds for classical simple Lie algebras, and their asymptotic expansions

We derive formulas for the Reshetikhin-Turaev invariants of all oriented Seifert manifolds associated to an arbitrary complex finite dimensional simple Lie algebra $\mathfrak g$ in terms of the Seifert invariants and standard data for $\mathfrak g$. A main corollary is a determination of the full asymptotic expansions of these invariants for lens spaces in the limit of large quantum level. Our results are in agreement with the asymptotic expansion conjecture due to J. E. Andersen.

math.GT↗