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T Hashimoto,
K Ohta,
K Aoki,
I Tanaka,
K. Yabe,
N Kawai,
W. Aoki,
H. Furusawa,
T Hattori,
M. Iye, [......],
Y. Shirasaki,
M Suzuki,
A. Tajitsu,
T Takata,
T Tamagawa,
H Terada,
T. Totani,
J Watanabe,
T Yamada,
A Yoshida
[show abstract]
[hide abstract]
ABSTRACT: 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. Comment: 22 pages, 10 figures, accepted for publication in The Astrophysical Journal
03/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We present a photometric survey of the stellar halo of the Andromeda galaxy, using Suprime-Cam on the Subaru Telescope. A detailed analysis of VI color-magnitude diagrams of the resolved stellar population is used to measure properties such as line-of-sight distance, surface brightness, metallicity, and age, and these are used to isolate and characterize different components of the M31 halo: (1) several substructures, and (2) the smooth halo. First, we study M31's halo substructure along the north-west/south-east minor axis out to R ~ 100 kpc and the south-west major axis region at R ~ 60 kpc. We confirm two substructures in the south-east halo reported by Ibata et al. (2007) and discover two overdense substructures in the north-west halo. We investigate the properties of these four substructures as well as other structures including the western shelf and find that differences in stellar populations among these systems, thereby suggesting each has a different origin. Our statistical analysis implies that the M31 halo as a whole may contain at least 16 substructures, each with a different origin. Second, we investigate the properties of an underlying, smooth and extended halo component out to R > 100 kpc. We find that the surface density of this smooth halo can be fitted to a Hernquist model of scale radius ~ 17 kpc or a power-law profile with ~ R^{-2.17 +/- 0.15}. In contrast to the relative smoothness of the halo density profile, its metallicity distribution appears to be spatially non-uniform with non-monotonic variations with radius, suggesting that the halo population has not had sufficient time to dynamically homogenize the accreted populations. Further implications for the formation of the M31 halo are discussed. Comment: 40 pages, 44 figures, accepted for publication in the ApJ. High resolution version available at http://www.astr.tohoku.ac.jp/~mikito/AndromedaHalo.pdf
The Astrophysical Journal 08/2009; · 6.02 Impact Factor
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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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P. Capak,
H. Aussel,
M. Ajiki,
H. J. McCracken,
B. Mobasher,
N. Scoville,
P. Shopbell,
Y. Taniguchi,
D. Thompson,
S. Tribiano, [......],
C. Scarlata,
D. Schiminovich,
E. Schinnerer,
M. Scodeggio,
K. Sheth,
Y. Shioya,
L. A. M. Tasca,
J. E. Taylor,
L. Yan,
and G. Zamorani
[show abstract]
[hide abstract]
ABSTRACT: We present imaging data and photometry for the COSMOS survey in 15 photometric bands between 0.3 and 2.4 μm. These include data taken on the Subaru 8.3 m telescope, the KPNO and CTIO 4 m telescopes, and the CFHT 3.6 m telescope. Special techniques are used to ensure that the relative photometric calibration is better than 1% across the field of view. The absolute photometric accuracy from standard-star measurements is found to be 6%. The absolute calibration is corrected using galaxy spectra, providing colors accurate to 2% or better. Stellar and galaxy colors and counts agree well with the expected values. Finally, as the first step in the scientific analysis of these data we construct panchromatic number counts which confirm that both the geometry of the universe and the galaxy population are evolving.
The Astrophysical Journal Supplement Series 12/2008; 172(1):99. · 13.46 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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K. S. Kawabata,
J. Deng,
L. Wang,
P. Mazzali,
K. Nomoto,
K. Maeda,
N. Tominaga,
H. Umeda,
M. Iye,
G. Kosugi, [......],
N. Kobayashi, Y. Komiyama,
Y. Mizumoto,
J. Noumaru,
R. Ogasawara,
K. Sekiguchi,
Y. Shirasaki,
T. Totani,
J. Watanabe,
and T. Yamada
[show abstract]
[hide abstract]
ABSTRACT: 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 ~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 Å), 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. 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 Astrophysical Journal 12/2008; 593(1):L19. · 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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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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T. Murayama,
Y. Taniguchi,
N. Z. Scoville,
M. Ajiki,
D. B. Sanders,
B. Mobasher,
H. Aussel,
P. Capak,
A. Koekemoer,
Y. Shioya, [......],
D. Maccagni,
E. Schinnerer,
V. Smolčić,
S. Tribiano,
A. Cimatti, Y. Komiyama,
S. Miyazaki,
S. S. Sasaki,
J. Koda,
and H. Karoji
[show abstract]
[hide abstract]
ABSTRACT: We present results from a narrowband optical survey of a contiguous area of 1.95 deg2, covered by the Cosmic Evolution Survey (COSMOS). Both optical narrowband (λc = 8150 Å and Δλ = 120 Å) and broadband (B , V, g', r', i', and z') imaging observations were performed with the Subaru prime-focus camera, Suprime-Cam on the Subaru Telescope. We provide the largest contiguous narrowband survey, targeting Lyα emitters (LAEs) at z ≈ 5.7. We find a total of 119 LAE candidates at z ~ 5.7. Over the wide-area covered by this survey, we find no strong evidence for large-scale clustering of LAEs. We estimate a star formation rate (SFR) density of ~7 × 10-4 M☉ yr-1 Mpc-3 for LAEs at z ≈ 5.7 and compare it with previous measurements.
The Astrophysical Journal Supplement Series 12/2008; 172(1):523. · 13.46 Impact Factor
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S. S. Sasaki,
Y. Taniguchi,
N. Scoville,
B. Mobasher,
H. Aussel,
D. B. Sanders,
A. Koekemoer,
M. Ajiki, Y. Komiyama,
S. Miyazaki, [......],
L. Hainline,
A. Renzini,
M. Giavalisco,
O. Le Fèvre,
C. Impey,
M. Elvis,
S. Lilly,
M. Rich,
E. Schinnerer,
and K. Sheth
[show abstract]
[hide abstract]
ABSTRACT: We report on the discovery of a new potential galaxy threshing system in the COSMOS 2 square degree field using the prime-focus camera, Suprime-Cam, on the 8.2 m Subaru Telescope. This system consists of a giant elliptical galaxy with MV ≈ -21.6 and a tidally disrupted satellite galaxy with MV ≈ -17.7 at a photometric redshift of z ≈ 0.08. This redshift is consistent with the spectroscopic redshift of 0.079 for the giant elliptical galaxy obtained from the Sloan Digital Sky Survey (SDSS) archive. The luminosity masses of the two galaxies are 3.7 × 1012 and 3.1 × 109 ☉, respectively. The distance between the two galaxies is greater than 100 kpc. The two tidal tails emanating from the satellite galaxy extend over 150 kpc. This system would be the second well-defined galaxy threshing system found so far.
The Astrophysical Journal Supplement Series 12/2008; 172(1):511. · 13.46 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: A large spectroscopic survey is constructed of galaxies in the Coma Cluster. The survey covers a wide area (1 deg2) to deep magnitudes (R ~ 19.5), covering both the core (high density) and outskirts (intermediate to low density) of the cluster. The spectroscopic sample consists of a total of 1191 galaxies, of which 760 are confirmed members of the Coma Cluster. A statistical technique is developed to correct the spectroscopic sample for incompleteness. The corrected sample is then used to construct an R-band luminosity function (LF) spanning a range of 7 mag (-23 < MR - 5 log h65 < -16) at both the core and outskirts of the cluster. The R-band LF for the entire Coma Cluster, fitted to Schechter form, gives M = -21.79 + 5 log h65 and α = -1.18. Dependence of the LF on local environment in Coma is explored. The LFs are found to be the same, within the errors, between the inner and outer regions and close to those from recent measurements for field galaxies. This is remarkable given the variation in the spectral types of galaxies between field and cluster environments. The steep faint-end slope for the LFs, observed in previous studies using photometric surveys, is not found here. However, the LF in this study is only measured to MR = -16, compared to much deeper limits (MR ~ -12) achieved in photometric surveys. The total B-band LF for the Coma Cluster, fitted to a Schechter form, is M = -19.95 + 5 log h65 and α = -0.96. This also shows a dip at M = -18 mag, in agreement with previous studies. The implications of this feature are discussed. The LF is studied in B-R color intervals and shows a steep faint-end slope for red (B-R > 1.35) galaxies, at both the core and outskirts of the cluster. This population of low-luminosity red galaxies has a higher surface density than the blue (B-R < 1.35) star-forming population and dominates the faint end of the Coma Cluster LF. It is found that the relative number of high surface brightness galaxies is larger at the cluster core, implying the destruction of low surface brightness galaxies in the dense core environment.
The Astrophysical Journal 12/2008; 587(2):605. · 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 found an unusual complex of narrow blue filaments, bright blue knots, and H-alpha emitting filaments and clouds, which morphologically resembled a complex of ``fireballs,'' extending up to 80 kpc south from an E+A galaxy RB199 in the Coma cluster. The galaxy has a highly disturbed morphology indicative of a galaxy--galaxy merger remnant. The narrow blue filaments extend in straight shapes toward the south from the galaxy, and several bright blue knots are located at the southern ends of the filaments. The Rc band absolute magnitudes, half light radii and estimated masses of the bright knots are -12 - -13 mag, 200 - 300 pc and 10^6-7 Msolar, respectively. Long, narrow H-alpha emitting filaments are connected at the south edge of the knots. The average color of the fireballs is B - Rc = 0.5, which is bluer than RB199 (B - R = 0.99), suggesting that most of the stars in the fireballs were formed within several times 10^8 yr. The narrow blue filaments exhibit almost no H-alpha emission. Strong H-alpha and UV emission appear in the bright knots. These characteristics indicate that star formation recently ceased in the blue filaments and now continues in the bright knots. The gas stripped by some mechanism from the disk of RB199 may be traveling in the intergalactic space, forming stars left along its trajectory. The most plausible fireball formation mechanism is ram pressure stripping by high-speed collision between the galaxy and the hot intra-cluster medium. The fireballs may be a snapshot of diffuse intra-cluster population formation, or halo star population formation in a cluster galaxy. Comment: 13 pages, 14 figures, submitted to ApJ
07/2008;
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P. Capak,
H. Aussel,
M. Ajiki,
H. J. McCracken,
B. Mobasher,
N. Scoville,
P. Shopbell,
Y. Taniguchi,
D. Thompson,
S. Tribiano, [......],
C. Scarlata,
D. Schiminovich,
E. Schinnerer,
M. Scodeggio,
K. Sheth,
Y. Shioya,
L. A. M. Tasca,
J. E. Taylor,
L. Yan,
G. Zamorani
[show abstract]
[hide abstract]
ABSTRACT: The present COSMOS data were collected on a variety of telescopes and
instruments, as well as from the Sloan Digital Sky Survey (SDSS) second
data release (DR2) archive (u, g, r, i, z) and Hubble Space Telescope
(HST, F814W). This paper covers the processing of the data obtained with
Suprime-Cam on the Subaru 8.3m telescope (Bj, Vj, g+, r+, i+, z+,
NB816), Megaprime on the 3.6m Canada-France-Hawaii Telescope (CFHT, u*,
i*), FLAMINGOS on the Kitt Peak National Observatory (KPNO, Ks) 4m
telescope, and the Infrared Side Port Imager on the Cerro Tololo
Inter-American Observatory (CTIO, Ks) 4m telescope during the 2004-2005
observing season.
The COSMOS I band catalog is an I band selected multi-color catalog for
2 square degrees centered on the COSMOS field at 10:00:28.6, +02:12:21.
The total magnitude (SExtractor mag_auto) for a source must have an AB
magnitude of less than i+<25 to appear in the archival catalog. All
photometry is in the AB magnitude system and measured in a 3 arc second
aperture on PSF-matched images unless otherwise noted. A magnitude of
-99 indicates a photometric measurement was not possible due to lack of
data, a large number of bad pixels, or saturation. A magnitude of 99.0
indicates no detection. In the case of no detection the error given for
the object is the 1 sigma limiting magnitude at the position of the
souce.
The photometry is as measured on the images with no corrections applied.
We recommend applying the magnitude offsets in the paper to obtain the
best possible photometry. More details on the photometry are available
in the paper. The Photometric Redshifts included in this catalog are
described in Mobasher et al. (2007ApJS..172..117M) and have an accuracy
of dz/(1+z)<0.031 at z<1.2 and I<24.
It is important to pay attention to the flag columns at the end of the
catalog. The cleanest catalog will have all flags set to 0. The
photometry flags indicate the area of the photometry aperture, in square
arc seconds, which is in a masked region. A flag of 1 indicates 14
percent of the aperture is masked, so any flagged object should be
carefully checked. Objects with a de-blending flag set to 1 are
potentially spurious and should not be used for statistical studies.
However, the photometry for real sources with a de-blending flag set to
1 is good if they fall outside of masked region.
(1 data file).
VizieR Online Data Catalog. 02/2008; 217:20099.
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12/2007: pages 335-336;
-
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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ABSTRACT: We report the serendipitous findings of 13 faint meteors and 44 artificial space objects by Subaru SuprimeCam imaging observations during 11-16 August 2004. The meteors, at about 100km altitude, and artificial satellites/debris in orbit, at 500km altitude or higher, were clearly discriminated by their apparent defocused image sizes. CCD photometry of the 13 meteors, including 1 Perseid, 1 Aquarid, and 11 sporadic meteors, was performed. We defined a peak video-rate magnitude by comparing the integrated photon counts from the brightest portion of the track traversed within 33ms to those from a 0-mag star during the same time duration. This definition gives magnitudes in the range 4.0< V_{vr} <6.4 and 4.1< I_{vr}<5.9 for these 13 meteors. The corresponding magnitude for virtual naked-eye observers could be somewhat fainter especially for the V-band observation, in which the [OI] 5577 line lasting about 1 sec as an afterglow could contribute to the integrated flux of the present 5-10 min CCD exposures. Although the spatial resolution is insufficient to resolve the source size of anything smaller than about 1 m, we developed a new estimate of the collisionally excited column diameter of these meteors. A diameter as small as a few mm was derived from their collisionally excited photon rates, meteor speed, and the volume density of the oxygen atoms at the 100km altitude. The actual column diameter of the radiating zone, however, could be as large as few 100m because the excited atoms travel that distance before they emit forbidden lines in 0.7 sec of its average lifetime. Among the 44 artificial space objects, we confirmed that 17 were cataloged satellites/space debris.
05/2007;
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T Murayama,
Y Taniguchi,
N. Z. Scoville,
M. Ajiki,
D. B. Sanders,
B. Mobasher,
H. Aussel,
P. Capak,
A. Koekemoer,
Y. Shioya, [......],
D. Maccagni,
E. Schinnerer,
V. Smolcic,
S. Tribiano,
A. Cimatti, Y Komiyama,
S Miyazaki,
S. S. Sasaki,
J. Koda,
H. Karoji
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ABSTRACT: We present results from a narrow-band optical survey of a contiguous area of 1.95 deg^2, covered by the Cosmic Evolution Survey (COSMOS). Both optical narrow-band (lambda_c = 8150 AA and Delta_lambda = 120 AA) and broad-band (B, V, g', r', i', and z') imaging observations were performed with the Subaru prime-focus camera, Suprime-Cam on the Subaru Telescope. We provide the largest contiguous narrow-band survey, targetting Ly alpha emitters (LAEs) at z~5.7. We find a total of 119 LAE candidates at z~5.7. Over the wide-area covered by this survey, we find no strong evidence for large scale clustering of LAEs. We estimate a star formation rate (SFR) density of ~7*10^-4 M_sun yr^-1 Mpc^-3 for LAEs at z~5.7, and compare it with previous measurements. Comment: 26 pages, 19 figures. to appear in the ApJ Supplement COSMOS Special Issue
02/2007;
