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S. Ikarashi,
K. Kohno,
J. E. Aguirre,
I. Aretxaga,
V. Arumugam,
J. E. Austermann,
J. J. Bock,
C. M. Bradford,
M. Cirasuolo,
L. Earle, [......], K. Shimasaku,
T. Takagi,
T. Takata,
Y. Tamura,
K. Tanaka,
T. Tsukagoshi,
D. J. Wilner,
G. W. Wilson,
M. S. Yun,
J. Zmuidzinas
[show abstract]
[hide abstract]
ABSTRACT: We report on the detection of an extremely bright (∼37 mJy at 1100 μm and ∼91 mJy at 880 μm) submillimetre galaxy (SMG), AzTEC-ASTE-SXDF1100.001 (hereafter referred to as SXDF1100.001 or Orochi), discovered in the 1100 μm observations of the Subaru/XMM–Newton Deep Field using AzTEC on ASTE. Subsequent CARMA 1300-μm and SMA 880-μm observations successfully pinpoint the location of Orochi and suggest that it has two components, one extended [full width at half-maximum (FWHM) of ∼4 arcsec] 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 were found. The derived upper limit to the line-to-continuum flux ratio is 0.1–0.3 (2σ) 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 ∼ 3.4 behind a foreground, optically visible (but red) galaxy at z ∼ 1.4. The deduced apparent (i.e., no correction for magnification) infrared luminosity (LIR) and star formation rate (SFR) are 6 × 1013 L⊙ and 11 000 M⊙ yr−1, respectively, assuming that the LIR is dominated by star formation. These values suggest that Orochi will consume its gas reservoir within a short time-scale (3 × 107 yr), which is indeed comparable to those in extreme starbursts like the centres of local ultraluminous infrared galaxies (ULIRGs).
Monthly Notices of the Royal Astronomical Society 08/2011; 415(4):3081 - 3096. · 4.90 Impact Factor
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S. Ikarashi,
K Kohno,
J. E. Aguirre,
I. Aretxaga,
V. Arumugam,
J. E. Austermann,
J. J. Bock,
C. M. Bradford,
M. Cirasuolo,
L. Earle, [......], K. Shimasaku,
T Takagi,
T Takata,
Y Tamura,
K Tanaka,
T. Tsukagoshi,
D. J. Wilner,
G W Wilson,
M. S. Yun,
J. Zmuidzinas
[show abstract]
[hide abstract]
ABSTRACT: We report the detection of an extremely bright ($\sim$37 mJy at 1100 $\mu$m
and $\sim$91 mJy at 880 $\mu$m) submillimeter galaxy (SMG),
AzTEC-ASTE-SXDF1100.001 (hereafter referred to as SXDF1100.001 or Orochi),
discovered in 1100 $\mu$m observations of the Subaru/XMM-Newton Deep Field
using AzTEC on ASTE. Subsequent CARMA 1300 $\mu$m and SMA 880 $\mu$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 $\sigma$) 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.
09/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We present the discovery of a large-scale structure of emission-line galaxies at redshift z= 4.86 behind a massive cluster of galaxies, A1689. Previous spectroscopic observations of a galaxy, A1689−7.1 at z= 4.87, near this structure, revealed a possible overdense region of intergalactic medium (IGM) around the galaxy, which extends at least ∼80 comoving Mpc along the line of sight. In order to investigate whether this z∼ 5 IGM overdense region contains a galaxy overdensity, we undertook narrow- and broad-band imaging observations around A1689−7.1 with Subaru/Suprime-Cam. We detected 51 candidates as Ly emitters at redshift z= 4.86 ± 0.03 in the 32 × 24 arcmin2 field of view. After correction for lensing by the foreground cluster, we found a large-scale (∼20 × 60 comoving Mpc) overdense region of galaxies around A1689−7.1 in the source plane at z= 4.86. The densest peak in this region has an overdensity of δ∼ 4, suggesting that this structure is probably a good candidate for a protocluster which may evolve into a massive cluster of galaxies in the present-day Universe. A1689−7.1 is located at the edge of this region, where the local galaxy density is ∼1.6 times the mean density and is close to the density contrast in the IGM along the line of sight to A1689−7.1 estimated from the optical depth. The overdensities of galaxies we have found may suggest that at least some parts of the IGM overdense region have already started to form galaxies and moreover they relate to the formation of a protocluster. Although we lack information on the three-dimensional distributions of both IGM and galaxy overdense regions, the similarity of the scales of both regions may suggest that the two are parts of a single large-scale structure, which would be an large edge-on sheet along the line of sight with a size of ∼20 × 60 × 80 comoving Mpc.
Monthly Notices of the Royal Astronomical Society Letters 01/2010; 403(1):L54 - L58.
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[show abstract]
[hide abstract]
ABSTRACT: We present the discovery of a large-scale structure of emission-line galaxies at redshift z=4.86 behind a massive cluster of galaxies, A1689. Previous spectroscopic observations of a galaxy, A1689-7.1 at z=4.87, near this structure, revealed a possible overdense region of inter-galactic medium (IGM) around the galaxy, which extends at least ~80 comoving Mpc along the line of sight. In order to investigate whether this z~5 IGM overdense region contains a galaxy overdensity, we undertook narrow- and broad-band imaging observations around A1689-7.1 with Subaru/Suprime-Cam. We detected 51 candidate Ly-alpha emitters at redshift z=4.86+-0.03 in the 32 x 24 arcmin^2 field of view. After correction for lensing by the foreground cluster, we found a large-scale (~20 x 60 comoving Mpc) overdense region of galaxies around A1689-7.1 in the source plane at z=4.86. The densest peak in this region has an overdensity of delta~4, suggesting that this structure is probably a good candidate for a protocluster. A1689-7.1 is located at the edge of this region, where the local galaxy density is ~1.6 times the mean density and is close to the density contrast in the IGM along the line of sight to A1689-7.1 estimated from the optical depth. The overdensities of galaxies we have found may suggest that at least some parts of the IGM overdense region have already started to form galaxies and moreover they relate to the formation of a protocluster. Although we lack information on the three dimensional distributions of both IGM and galaxy overdense regions, the similarity of the scales of both regions may suggest that the two are parts of a single large-scale structure, which would be an large edge-on sheet along the line of sight with a size of ~20 x 60 x 80 comoving Mpc. Comment: 6 pages, 4 figures, accepted for publication in MNRAS
01/2010;
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Bianca M. Poggianti,
Terry J. Bridges,
Dave Carter,
Bahram Mobasher,
M. Doi,
M. Iye,
N. Kashikawa,
Y. Komiyama,
S. Okamura,
M. Sekiguchi, K. Shimasaku,
M. Yagi,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: The ages of stellar populations in 52 elliptical and S0 galaxies in the Coma Cluster are investigated, using a new spectroscopic sample. More than 40% of the S0's are found to have undergone star formation in their central regions during the last ~5 Gyr, while such activity is absent in the ellipticals. Galaxies in this sample have absolute magnitudes in the range -20.5 < MB < -17.5, and the fraction of S0 galaxies with recent star formation is higher at fainter luminosities. The observed luminosity range of S0 galaxies with signs of recent star formation activity is consistent with them being the descendants of typical star-forming spirals at intermediate redshift whose star formation has been halted as a consequence of the dense environment.
The Astrophysical Journal 12/2008; 563(1):118. · 6.02 Impact Factor
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Bahram Mobasher,
Terry J. Bridges,
Dave Carter,
Bianca M. Poggianti,
Y. Komiyama,
N. Kashikawa,
M. Doi,
M. Iye,
S. Okamura,
M. Sekiguchi, K. Shimasaku,
M. Yagi,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: This is the second paper in a series studying the photometric and spectroscopic properties of galaxies of different luminosities in the Coma Cluster. We present the sample selection, spectroscopic observations, and completeness functions. To study the spectral properties of galaxies as a function of their local environment, two fields were selected for spectroscopic observations to cover both the core (Coma 1) and outskirts (i.e., southwest of the core and centered on NGC 4839; Coma 3) of the cluster. To maximize the efficiency of spectroscopic observations, two subsamples were defined, consisting of "bright" and "faint" galaxies, both drawn from magnitude-limited parent samples. Medium-resolution spectroscopy (6-9 Å) was then carried out for a total of 490 galaxies in both fields (302 in Coma 1 and 188 in Coma 3), using the WYFFOS multifiber spectrograph on the William Herschel Telescope. The galaxies cover a range of 12 < R < 20, corresponding to -23 < MR < -15 (H0 = 65 km s-1 Mpc-1). The redshifts for these galaxies are measured with an accuracy of 75 km s-1. The spectral line strengths and equivalent widths are also measured for the same galaxies and analyzed in the next paper of this series. A total of 189 (Coma 1) and 90 (Coma 3) galaxies are identified as members of the Coma Cluster. An analysis of the colors show that only two members of the Coma Cluster in our sample have B - R > 2. The completeness functions for our sample are calculated. These show that the bright sample is 65% complete at R < 17 mag, becoming increasingly incomplete toward fainter magnitudes, while the faint sample follows a monotonically decreasing completeness function at R > 19 mag.
The Astrophysical Journal Supplement Series 12/2008; 137(2):279. · 13.46 Impact Factor
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David Carter,
Bahram Mobasher,
Terry J. Bridges,
Bianca M. Poggianti,
Y. Komiyama,
N. Kashikawa,
M. Doi,
M. Iye,
S. Okamura,
M. Sekiguchi, K. Shimasaku,
M. Yagi,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: We investigate the radial dependence of the spectroscopic properties, in particular the Mg2, Fe, and Hβ spectroscopic indices, in a sample of galaxies spanning a wide range of absolute luminosity in the Coma Cluster. After allowing for the magnitude dependence of these indices, we find a significant gradient in Mg2, in the sense that galaxies in the core of the cluster have stronger Mg2. We find only weak gradients in Fe and Hβ. Using the model grids presented in an earlier paper in this series, we attribute the Mg2 gradient to changes in metal abundance. One possible mechanism to create this abundance gradient is pressure confinement by the intracluster medium of material from supernova-driven winds early in the history of the galaxies.
The Astrophysical Journal 12/2008; 567(2):772. · 6.02 Impact Factor
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Bianca M. Poggianti,
Terry J. Bridges,
Bahram Mobasher,
Dave Carter,
M. Doi,
M. Iye,
N. Kashikawa,
Y. Komiyama,
S. Okamura,
M. Sekiguchi, K. Shimasaku,
M. Yagi,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: We present a detailed analysis of the spectroscopic catalog of galaxies in the Coma Cluster from Mobasher et al. (Paper II of the series). This catalog comprises ~300 spectra of cluster members with absolute magnitudes in the range MB = -20.5 to -14 in two areas of ~1 × 1.5 Mpc toward the center and the southwest region of the cluster. In order to study the star formation and metallicity properties of the Coma galaxies as a function of their luminosity and environment, spectral indices of the Lick/IDS system and equivalent widths of the emission lines were measured in the range λ = 3600-6600 Å. In this paper, the analysis is restricted to the 257 galaxies with no emission lines in their spectra. The strength of the age-sensitive indices (such as Hβ, HγF, and HδF) is found to correlate with galaxy magnitude over the whole magnitude range explored in this study. Similarly, the metallicity-sensitive indices (such as Mg2, Fe, and C24668) anticorrelate with magnitude. By comparing the observed indices with model grids based on the Padova isochrones, we derive luminosity-weighted ages and metallicities. We present the distributions of ages and metallicities for galaxies in various magnitude bins. The mean metallicity decreases with galaxy magnitude and, at a given luminosity, appears to be generally lower for galaxies in the southwest region of Coma as compared to the center of the cluster. A broad range of ages, from younger than 3 Gyr to older than 9 Gyr, is found in galaxies of any magnitude. However, systematic trends of age with luminosity are present among galaxies in the central field, including a slight decrease of the mean age for fainter galaxies. Furthermore, in the central Mpc of Coma, a large fraction of galaxies at any luminosity (50%-60% of the giants, more than 30% of the dwarfs) show no evidence in their central regions of star formation occurred at redshift z < 2, while the proportion of galaxies with significant star formation occurring at intermediate (0.35 < z < 2) and low (z < 0.35) redshifts is found to depend on galaxy luminosity. An additional surprising result is that the faint galaxies with young luminosity-weighted ages appear to have a bimodal metallicity distribution that, if confirmed, would point to a composite formation scenario involving different physical processes. Coadding the spectra of these metal-rich and metal-poor galaxies separately supports the reality of the metallicity bimodality, although higher signal-to-noise ratio spectra of the individual galaxies will be needed to draw definite conclusions. An anticorrelation between age and metallicity is found to be present in galaxies of any given luminosity bin, and it is especially evident among the brightest subset with the highest signal-to-noise ratio spectra. Finally, we present an interpretation of the index-magnitude relations observed. We show that the slopes of the indices/magnitude relations are the consequence of both age and metallicity trends with luminosity: each such trend on its own would be sufficient to produce relations similar to those observed.
The Astrophysical Journal 12/2008; 562(2):689. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We reported in a previous paper the discovery of a large-scale structure of Lyα emitters (LAEs) at z = 4.86 ± 0.03 with a projected size of 20 h Mpc × 50 h Mpc in narrowband data of a 25' × 45' area of the Subaru Deep Field (Ω0 = 0.3, λ0 = 0.7, and H0 = 70 h70 km s-1 Mpc-1). However, the surveyed area, which corresponds to 55 h Mpc × 100 h Mpc, was not large enough to conclude that what we were seeing was a typical distribution of z 5 LAEs. In this Letter, we report the results of follow-up imaging of the same sky area using a new narrowband filter (NB704, λc = 7046 Å and FWHM = 100 Å) to detect LAEs at z = 4.79, i.e., LAEs lying closer to us by 39 h 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 function are thus largely different between the two samples. These results demonstrate a large cosmic variance in the clustering properties of LAEs on scales of ~50 h Mpc.
The Astrophysical Journal 12/2008; 605(2):L93. · 6.02 Impact Factor
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T. Nagao,
Y. Taniguchi,
N. Kashikawa,
K. Kodaira,
N. Kaifu,
H. Ando,
H. Karoji,
M. Ajiki,
M. Akiyama,
K. Aoki, [......],
Y. Sato,
K. Sekiguchi, K. Shimasaku,
Y. Shioya,
H. Tamura,
I. Tanaka,
M. Umemura,
T. Yamada,
N. Yasuda,
and M. Yoshida
[show abstract]
[hide abstract]
ABSTRACT: 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 Lyα emitter with only very faint ultraviolet continuum. The rest-frame equivalent width of the detected Lyα emission is as much as 130 Å. Thus the light detected in our z' image is largely attributed to the Lyα emission, i.e., ~40% of the z'-band flux is the strong Lyα 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.
The Astrophysical Journal 12/2008; 613(1):L9. · 6.02 Impact Factor
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K. Shimasaku,
M. Ouchi,
S. Okamura,
N. Kashikawa,
M. Doi,
H. Furusawa,
M. Hamabe,
T. Hayashino,
K. Kawabata,
M. Kimura, [......],
F. Nakata,
K. Ohta,
Y. Ohyama,
M. Sekiguchi,
Y. Shioya,
H. Tamura,
Y. Taniguchi,
M. Yagi,
T. Yamada,
and N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of a large-scale structure of Lyα 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' × 45' area of the Subaru Deep Field in a narrow band (NB711, λc = 7126 Å and FWHM = 73 Å) 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 ~20%. 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 H0 = 70 km s-1 Mpc-1, Ω0 = 0.3, and λ0 = 0.7). This elongated region includes a circular region of 12 Mpc radius of higher surface overdensity (δΣ = 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 Ω0 = 0.3 flat model with σ8 = 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 6. This value suggests that the typical mass of dark halos hosting LAEs at z 5 is of the order of 1012 M☉. Such a large mass poses an interesting question about the nature of LAEs.
The Astrophysical Journal 12/2008; 586(2):L111. · 6.02 Impact Factor
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Ravi K. Sheth,
Mariangela Bernardi,
Paul L. Schechter,
Scott Burles,
Daniel J. Eisenstein,
Douglas P. Finkbeiner,
Joshua Frieman,
Robert H. Lupton,
David J. Schlegel,
Mark Subbarao, K. Shimasaku,
Neta A. Bahcall,
J. Brinkmann,
and Željko Ivezić
[show abstract]
[hide abstract]
ABSTRACT: The distribution of early-type galaxy velocity dispersions, (σ), is measured using a sample drawn from the Sloan Digital Sky Survey database. Its shape differs significantly from that obtained by simply using the mean correlation between luminosity L and velocity dispersion σ to transform the luminosity function into a velocity function: ignoring the scatter around the mean σ-L relation is a bad approximation. An estimate of the contribution from late-type galaxies is also made, which suggests that (σ) is dominated by early-type galaxies at velocities larger than ~200 km s-1.
The Astrophysical Journal 12/2008; 594(1):225. · 6.02 Impact Factor
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Y. Komiyama,
M. Sekiguchi,
N. Kashikawa,
M. Yagi,
M. Doi,
M. Iye,
S. Okamura, K. Shimasaku,
N. Yasuda,
B. Mobasher,
D. Carter,
T. J. Bridges,
and B. M. Poggianti
[show abstract]
[hide abstract]
ABSTRACT: We carried out a deep photometric and spectroscopic survey of wide areas in the Coma cluster, aiming to investigate the properties of galaxy population in different environments within the cluster. We present the results in a series of papers. This paper, the first of the series, describes the imaging observations and photometric data reduction. Imaging data were taken with the wide-field mosaic CCD camera, which was attached to the prime focus of the 4.2 m William Herschel Telescope at La Palma, Canary Islands. Our observations covered a large field of view (2.22 deg2) from the cluster center to the outskirts, and our photometry is complete to a limiting magnitude of R 23 mag. The limit of secure star-galaxy discrimination is, however, brighter at R = 20 mag. We identified 3147 galaxies down to this limit in the part (1.32 deg2) of the survey area, together with 662 galaxies identified in the control field SA 57. We measured surface photometric parameters and compiled a photometric catalog for these galaxies. Statistical properties of the catalog are shown in this paper, while the catalog itself is given in a forthcoming paper in the series.
The Astrophysical Journal Supplement Series 12/2008; 138(2):265. · 13.46 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We study the dependence of the clustering strength on stellar mass and
star-formation rate for Lyman-break galaxies (LBGs), using a sample of
708 LBG candidates at z˜ 3. This sample is constructed from deep
multi-waveband imaging data from optical to near-infrared wavelengths in
the Subaru/XMM-Newton Deep Field. We find that the correlation length
strongly depends on a combination of rest-frame UV brightness (an
indicator of star-formation rate) and rest-frame optical brightness (an
indicator of stellar mass) in the sense that galaxies bright in optical
brightness have large correlation lengths irrespectively of ultraviolet
(UV) brightness, while galaxies faint in optical brightness have
correlation lengths decreasing with decreasing UV brightness. These
results indicate that galaxies with large stellar masses always belong
to massive halos in which they can have various star-formation rates,
while galaxies with small stellar masses reside in less-massive halos
only if they have lower star-formation rates. There appears to be an
upper limit to stellar mass and star-formation rate which is determined
by the mass of hosting halos.
09/2008; 399:276.
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[show abstract]
[hide abstract]
ABSTRACT: We present a clustering analysis for Lyman-break galaxies (LBGs) at z
˜ 3 -- 5 and K-band selected BzK galaxies at z ˜ 2 using
wide-field multi-color data on two blank fields: the Subaru Deep Field
and the Subaru/XMM-Newton Deep Field. We then combine our clustering
measurements with those taken from the literature, to discuss the
dependence of the star-formation rate and stellar mass of galaxies on
the mass of hosting dark haloes for high-z galaxies. We find that the
star-formation rate of LBGs linearly correlates with the mass of hosting
dark haloes, and that within rather large uncertainties, dusty
star-burst galaxies (distant red galaxies, ultra-luminous infrared
galaxies, and submillimeter galaxies) appear to be simple scaled-up
populations of LBGs in terms of their star-formation efficiency. We also
find a positive correlation between the stellar mass and the dark-halo
mass for K-selected galaxies. A detailed analysis for z ˜ 3 LBGs
reveals that there are upper limits on the star-formation rate and the
stellar mass which are determined by the mass of hosting dark haloes.
09/2008; 399:75.
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[show abstract]
[hide abstract]
ABSTRACT: We have been carrying out K-band wide-field and deep imaging of the
Subaru Deep Field (SDF) using WFCAM on UKIRT. The overlap with the
optical images exceeds
700 arcmin^2 with the a limiting magnitude of ˜23.5AB. The K-band
number counts of pBzKs show a "knee" around 20.5AB, which suggests the
deficit of <10^{11}M_{sun} passive galaxies at z˜1.5. This
can be explained by the down-sizing evolution of galaxies, and fraction
of galaxies are still under formation phase at z˜ 1.5.
09/2008; 399:274.
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E. Gunn,
M. Carr,
C. Rockosi,
M. Sekiguchi,
K. Berry,
B. Elms,
E. de Haas,
Ž. Ivezić,
G. Knapp,
R. Lupton, [......], K. Shimasaku,
N. Okada,
C. Hull,
W. Siegmund,
E. Mannery,
M. Blouke,
D. Heidtman,
D. Schneider,
R. Lucinio,
and J. Brinkman
[show abstract]
[hide abstract]
ABSTRACT: We have constructed a large-format mosaic CCD camera for the Sloan Digital Sky Survey. The camera consists of two arrays, a photometric array that uses 30 2048 × 2048 SITe/Tektronix CCDs (24 μm pixels) with an effective imaging area of 720 cm2 and an astrometric array that uses 24 400 × 2048 CCDs with the same pixel size, which will allow us to tie bright astrometric standard stars to the objects imaged in the photometric camera. The instrument will be used to carry out photometry essentially simultaneously in five color bands spanning the range accessible to silicon detectors on the ground in the time-delay–and–integrate (TDI) scanning mode. The photometric detectors are arrayed in the focal plane in six columns of five chips each such that two scans cover a filled stripe 25 wide. This paper presents engineering and technical details of the camera.
The Astronomical Journal 12/2007; 116(6):3040. · 4.03 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We investigate the total luminosity function (LF) and the type-specific luminosity functions (TSLFs)of r1/4-like galaxies and exponential-like galaxies in 10 nearby clusters. The composite total LF of the 10clusters is described well by the Schechter function with M = -21.3 and α = -1.31 in the range -23.5 < MR + 5 log h < -16. This value of α is consistent with the previous results for cluster galaxies. An extensive comparison of the values of α is made between clusters and fields. We find that the total LF of cluster galaxies has a steeper faint end slope than that of field galaxies. In contrast to the composite total LF, the individual total LFs of some clusters are not fitted well by the Schechter function. They show a hump around MR ~ -20 to -19 associated with a dip around MR ~ -19 to -18. The composite TSLFs of both r1/4-like galaxies and exponential-like galaxies are fitted well by the Schechter function. The best-fit parameters are (M = -21.2, α = -1.08) for the former and (M = -21.1, α = -1.49) for the latter. When seen on a cluster to cluster basis, however, the TSLFs of the two types of galaxies show different behaviors. The TSLF of r1/4-like galaxies shows a considerable diversity among the clusters, while the TSLF of exponential-like galaxies is similar in all the clusters. We demonstrate that the dip at MR ~ -19 to -18 seen in the total LFs of some clusters is almost entirely due to r1/4-like galaxies, rather than exponential-like galaxies. We find that the dip of the TSLF of r1/4-like galaxies is correlated with the velocity dispersion of the cluster in the sense that clusters with larger velocity dispersion show more distinct dips.
The Astronomical Journal 12/2007; 123(1):87. · 4.03 Impact Factor
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M. Arnaboldi,
K. C. Freeman,
S. Okamura,
N. Yasuda,
O. Gerhard,
N. R. Napolitano,
M. Pannella,
H. Ando,
M. Doi,
H. Furusawa,
M. Hamabe,
M. Kimura,
T. Kajino,
Y. Komiyama,
S. Miyazaki,
F. Nakata,
M. Ouchi,
M. Sekiguchi, K. Shimasaku,
and M. Yagi
[show abstract]
[hide abstract]
ABSTRACT: We have identified intracluster planetary nebulae (PNs) in a Virgo Cluster core field by imaging with the Subaru Suprime-Cam through two narrowband filters centered at the redshifted wavelengths of the [O III] λ5007 and the Hα 6563 Å lines; broadband images in V and R were acquired to check for emission in the adjacent continuum. Emission-line objects in Virgo are then selected from the two-color diagram [O III]-Hα versus [O III]-(V+R), which is calibrated using PNs in M84 (Jacoby et al.). Using both [O III] and Hα allows us to distinguish bona fide planetary nebulae from high-redshift emission-line galaxies at the bright end of the [O III] luminosity function. Spectroscopic observations of a subsample of these objects were made at the Telescopio Nazionale Galileo and at the Very Large Telescope in a region around M84 and in an intracluster field, respectively. The observations confirm the efficiency of the combined [O III]+Hα imaging to identify true PNs. We also obtained the first spectrum of an intracluster PN that shows the [O III] doublet with a signal-to-noise ratio greater than 10 and its Hα emission. From the results based on the spectroscopic follow-up, we derive a lower limit to the fraction of the Virgo Cluster light contributed by the intracluster stars at the surveyed position in the cluster core: it amounts to 10%.
The Astronomical Journal 12/2007; 125(2):514. · 4.03 Impact Factor
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T Takagi,
A. M. J. Mortier, K. Shimasaku,
K. Coppin,
A. Pope,
R. J. Ivison,
H. Hanami,
S. Serjeant,
D. L. Clements,
R. S. Priddey, [......],
S. A. Eales,
D. Farrah,
G. L. Granato,
M. Halpern,
D. H. Hughes,
E. van Kampen,
D Scott,
K Sekiguchi,
I. Smail,
M. Vaccari
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ABSTRACT: 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. Comment: 20 pages, 11 figures, accepted for publication in MNRAS
08/2007;
