-
Gordon T. Richards,
Charles R. Keeton,
Bartosz Pindor,
Joseph F. Hennawi,
Patrick B. Hall,
Edwin L. Turner,
Naohisa Inada,
Masamune Oguri, Shin-Ichi Ichikawa,
Robert H. Becker,
Michael D. Gregg,
Richard L. White,
J. Stuart B. Wyithe,
Donald P. Schneider,
David E. Johnston,
Joshua A. Frieman,
and J. Brinkmann
[show abstract]
[hide abstract]
ABSTRACT: We present seven epochs of spectroscopy on the quadruply imaged quasar SDSS J1004+4112, spanning observed-frame time delays from 1 to 322 days. The spectra reveal differences in the emission lines between the lensed images. Specifically, component A showed a strong enhancement in the blue wings of several high-ionization lines relative to component B, which lasted at least 28 days (observed frame) and then faded. Since the predicted time delay between A and B is 30 days, our time coverage suggests that the event was not intrinsic to the quasar. We attribute these variations to microlensing of part of the broad emission line region of the quasar, apparently resolving structure in the source plane on a scale of ~1016 cm at z = 1.734. In addition, we observed smaller differences in the emission-line profiles between components A and B that persisted throughout the time span, which may also be due to microlensing or millilensing. Further spectroscopic monitoring of this system holds considerable promise for resolving the structure of the broad emission line region in quasars.
The Astrophysical Journal 12/2008; 610(2):679. · 6.02 Impact Factor
-
Masamune Oguri,
Naohisa Inada,
Charles R. Keeton,
Bartosz Pindor,
Joseph F. Hennawi,
Michael D. Gregg,
Robert H. Becker,
Kuenley Chiu,
Wei Zheng, Shin-Ichi Ichikawa, [......],
Tomotsugu Goto,
James E. Gunn,
David E. Johnston,
Stephen M. Kent,
Robert C. Nichol,
Gordon T. Richards,
Hans-Walter Rix,
Donald P. Schneider,
Erin Scott Sheldon,
and Alexander S. Szalay
[show abstract]
[hide abstract]
ABSTRACT: We study the recently discovered gravitational lens SDSS J1004+4112, the first quasar lensed by a cluster of galaxies. It consists of four images with a maximum separation of 1462. The system was selected from the photometric data of the Sloan Digital Sky Survey (SDSS) and has been confirmed as a lensed quasar at z = 1.734 on the basis of deep imaging and spectroscopic follow-up observations. We present color-magnitude relations for galaxies near the lens plus spectroscopy of three central cluster members, which unambiguously confirm that a cluster at z = 0.68 is responsible for the large image separation. We find a wide range of lens models consistent with the data, and despite considerable diversity they suggest four general conclusions: (1) the brightest cluster galaxy and the center of the cluster potential well appear to be offset by several kiloparsecs; (2) the cluster mass distribution must be elongated in the north-south direction, which is consistent with the observed distribution of cluster galaxies; (3) the inference of a large tidal shear (~0.2) suggests significant substructure in the cluster; and (4) enormous uncertainty in the predicted time delays between the images means that measuring the delays would greatly improve constraints on the models. We also compute the probability of such large-separation lensing in the SDSS quasar sample on the basis of the cold dark matter model. The lack of large-separation lenses in previous surveys and the discovery of one in SDSS together imply a mass fluctuation normalization σ8 = 1.0 (95% confidence) if cluster dark matter halos have an inner density profile ρ r-1.5. Shallower profiles would require higher values of σ8. Although the statistical conclusion might be somewhat dependent on the degree of the complexity of the lens potential, the discovery of SDSS J1004+4112 is consistent with the predictions of the abundance of cluster-scale halos in the cold dark matter scenario.
The Astrophysical Journal 12/2008; 605(1):78. · 6.02 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We devise improved photometric parameters for the morphological classification of galaxies using a bright sample from the First Data Release of the Sloan Digital Sky Survey. In addition to using an elliptical aperture concentration index for classification, we introduce a new texture parameter, coarseness, which quantifies deviations from smooth galaxy isophotes. The elliptical aperture concentration index produces morphological classifications that are in appreciably better agreement with visual classifications than those based on circular apertures. With the addition of the coarseness parameter, the success rate of classifying galaxies into early and late types increases to 88% with respect to the reference visual classification. A reasonably high success rate (68%) is also attained in classifying galaxies into three types, early-type galaxies (E+S0) and early-type (Sa+Sb) and late-type (Sc+Sdm+Im) spiral galaxies.
The Astronomical Journal 12/2007; 130(4):1545. · 4.03 Impact Factor
-
Donald G. York,
J. Adelman,
John E. Anderson,
Jr,
Scott F. Anderson,
James Annis,
Neta A. Bahcall,
J. A. Bakken,
Robert Barkhouser,
Steven Bastian, [......],
Douglas L. Tucker,
Alan Uomoto,
Dan Vanden Berk,
Michael S. Vogeley,
Patrick Waddell,
Shu-i Wang,
Masaru Watanabe,
David H. Weinberg,
Brian Yanny,
and Naoki Yasuda
[show abstract]
[hide abstract]
ABSTRACT: The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and nonluminous matter in the universe: a photometrically and astrometrically calibrated digital imaging survey of π sr above about Galactic latitude 30° in five broad optical bands to a depth of g' ~ 23 mag, and a spectroscopic survey of the approximately 106 brightest galaxies and 105 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS and serves as an introduction to extensive technical on-line documentation.
The Astronomical Journal 12/2007; 120(3):1579. · 4.03 Impact Factor
-
J. Allyn Smith,
Douglas L. Tucker,
Stephen Kent,
Michael W. Richmond,
Masataka Fukugita,
Takashi Ichikawa, Shin-ichi Ichikawa,
Anders M. Jorgensen,
Alan Uomoto,
James E. Gunn, [......],
Alin Tolea,
Arne Henden,
James Annis,
Jeffrey R. Pier,
Timothy A. McKay,
Jon Brinkmann,
Bing Chen,
Jon Holtzman,
Kazuhiro Shimasaku,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We present the 158 standard stars that define the u'g'r'i'z' photometric system. These stars form the basis for the photometric calibration of the Sloan Digital Sky Survey. The defining instrument system and filters, the observing process, the reduction techniques, and the software used to create the stellar network are all described. We briefly discuss the history of the star selection process, the derivation of a set of transformation equations for the UBVRCIC system, and plans for future work.
The Astronomical Journal 12/2007; 123(4):2121. · 4.03 Impact Factor
-
Kazuhiro Shimasaku,
Masataka Fukugita,
Mamoru Doi,
Masaru Hamabe,
Takashi Ichikawa,
Sadanori Okamura,
Maki Sekiguchi,
Naoki Yasuda,
Jon Brinkmann,
István Csabai, Shin-Ichi Ichikawa,
Zeljko Ivezić,
Peter Z. Kunszt,
Donald P. Schneider,
Gyula P. Szokoly,
Masaru Watanabe,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We investigate the photometric properties of 456 bright galaxies using imaging data recorded during the commissioning phase of the Sloan Digital Sky Survey (SDSS). Morphological classification is carried out by correlating results of several human classifiers. Our purpose is to examine the statistical properties of color indices, scale lengths, and concentration indices as functions of morphology for the SDSS photometric system. We find that u'-g', g'-r', and r'-i' colors of SDSS galaxies match well with those expected from the synthetic calculation of spectroscopic energy distribution of template galaxies and with those transformed from UBVRCIC color data of nearby galaxies. The agreement is somewhat poor, however, for the i'-z' color band, with a discrepancy of 0.1–0.2 mag. With the aid of the relation between surface brightness and radius obtained by Kent in 1985, we estimate the averages of the effective radius of early-type galaxies and the scale length of exponential disks both to be 2.6 kpc for L* galaxies. We find that the half-light radius of galaxies depends slightly on the color bands, consistent with the expected distribution of star-forming regions for late-type galaxies and with the known color gradient for early-type galaxies. We also show that the (inverse) concentration index, defined by the ratio of the half-light Petrosian radius to the 90% light Petrosian radius, correlates tightly with the morphological type; this index allows us to classify galaxies into early (E/S0) and late (spiral and irregular) types, allowing for a 15%–20% contamination from the opposite class compared with eye-classified morphology.
The Astronomical Journal 12/2007; 122(3):1238. · 4.03 Impact Factor
-
Xiaohui Fan,
Michael A. Strauss,
Donald P. Schneider,
James E. Gunn,
Robert H. Lupton,
Brian Yanny,
Scott F. Anderson,
John E. Anderson,
Jr,
James Annis, [......],
Chris Stoughton,
Alexander S. Szalay,
Gyula P. Szokoly,
Douglas L. Tucker,
Michael S. Vogeley,
Patrick Waddell,
Shu-i Wang,
David H. Weinberg,
Naoki Yasuda,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We present photometric and spectroscopic observations of 15 high-redshift quasars (z > 3.6) discovered from ~140 deg2 of five-color (u', g', r', i', and z') imaging data taken by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. The quasars are selected by their distinctive colors in SDSS multicolor space. Four of the quasars have redshifts higher than 4.6 (z = 4.63, 4.75, 4.90, and 5.00, the latter being the highest redshift quasar yet known). In addition, two previously known z > 4 objects were recovered from the data. The quasars all have i* < 20 and have luminosities comparable to that of 3C 273. The spectra of the quasars have similar features (strong, broad emission lines and substantial absorption blueward of the Lyα emission line) seen in previously known high-redshift quasars. Although the photometric accuracy and image quality fail to meet the final survey requirements, our success rate for identifying high-redshift quasars (17 quasars from 27 candidates) is much higher than that of previous multicolor surveys. However, the numbers of high-redshift quasars found is in close accord with the number density inferred from previous surveys.
The Astronomical Journal 12/2007; 118(1):1. · 4.03 Impact Factor
-
Tomoki Morokuma,
Naohisa Inada,
Masamune Oguri, Shin-Ichi Ichikawa,
Yozo Kawano,
Kouichi Tokita,
Issha Kayo,
Patrick B. Hall,
Christopher S. Kochanek,
Gordon T. Richards,
Donald G. York,
and Donald P. Schneider
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of the two-image gravitationally lensed quasar SDSS J133222.62+034739.9 (SDSS J1332+0347) with an image separation of Δθ = 1.14''. This system consists of a source quasar at zs = 1.445 and a lens galaxy at zl = 0.191. The agreement of the luminosity, ellipticity, and position angle of the lens galaxy with those expected from a lens model confirms the lensing hypothesis.
The Astronomical Journal 12/2007; 133(1):214. · 4.03 Impact Factor
-
Naohisa Inada,
Masamune Oguri,
Bartosz Pindor,
Joseph F Hennawi,
Kuenley Chiu,
Wei Zheng, Shin-Ichi Ichikawa,
Michael D Gregg,
Robert H Becker,
Yasushi Suto, [......],
Gordon T Richards,
Hans-Walter Rix,
Erin Scott Sheldon,
Neta A Bahcall,
J Brinkmann,
Zeljko Ivezić,
Don Q Lamb,
Timothy A McKay,
Donald P Schneider,
Donald G York
[show abstract]
[hide abstract]
ABSTRACT: Gravitational lensing is a powerful tool for the study of the distribution of dark matter in the Universe. The cold-dark-matter model of the formation of large-scale structures (that is, clusters of galaxies and even larger assemblies) predicts the existence of quasars gravitationally lensed by concentrations of dark matter so massive that the quasar images would be split by over 7 arcsec. Numerous searches for large-separation lensed quasars have, however, been unsuccessful. All of the roughly 70 lensed quasars known, including the first lensed quasar discovered, have smaller separations that can be explained in terms of galaxy-scale concentrations of baryonic matter. Although gravitationally lensed galaxies with large separations are known, quasars are more useful cosmological probes because of the simplicity of the resulting lens systems. Here we report the discovery of a lensed quasar, SDSS J1004 + 4112, which has a maximum separation between the components of 14.62 arcsec. Such a large separation means that the lensing object must be dominated by dark matter. Our results are fully consistent with theoretical expectations based on the cold-dark-matter model.
Nature 01/2004; 426(6968):810-2. · 36.28 Impact Factor
-
Masamune Oguri,
Naohisa Inada,
Francisco J. Castander,
Michael D. Gregg,
Robert H. Becker, Shin-ichi Ichikawa,
Bartosz Pindor,
Jonathan Brinkmann,
Daniel J. Eisenstein,
Joshua A. Frieman,
Patrick B. Hall,
David E. Johnston,
Gordon T. Richards,
Paul L. Schechter,
Donald P. Schneider,
Alexander S. Szalay
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of the two-image gravitationally lensed quasar SDSS J1335+0118. The object was selected as a lens candidate from the Sloan Digital Sky Survey. The imaging and spectroscopic follow-up observations confirm that the system exhibits two gravitationally lensed images of a quasar at z=1.57. The image separation is 1.56''. We also detect an extended component between the two quasar images, likely the lensing galaxy. Preliminary mass modeling predicts the differential time delay \Delta t ~ 30 h^{-1} day assuming the redshift of the lens galaxy is 0.5.
12/2003;
-
[show abstract]
[hide abstract]
ABSTRACT: We devised a data format of a "Quick Look Information File (QLIF)" which
carries various information extracted from observational data, and have
developed a QLIF creation/browsing system, named "GYOJI", for the
evaluation of data obtained with Subaru Telescope. A QLIF accomodates a
two-dimensional image, typical profiles sampled from the image,
one-dimensional traces of spectra, and various pixel statistics. All
observational data of the telescope have a corresponding QLIF, and an
observer or a user of the archive system is able to inspect the
scientific information and the data quality from the QLIF without
accessing the original data of complex structure and a huge size.
Compared with the preview systems implemented in the astronomical
archive systems in the world, GYOJI is superior in providing much
information required for the data evaluation. This system has already
become an indispensable part of the archive system of Subaru Telescope,
and we think that this system has a great potential for the promotion of
database astronomy.
Publications of the National Astronomical Observatory of Japan. 02/2001; 6:49-57.
-
[show abstract]
[hide abstract]
ABSTRACT: The correlations between the photometric parameters and the
environmental parameters for 98 dwarf elliptical galaxies (dE's) in
seven 1°.5×1°.5 fields in the Virgo Cluster region are
investigated. Axial ratio, diameter, magnitude, mean surface brightness,
and concentration index taken from homogeneous surface photometry are
adopted as the photometric parameters, and projected distance from the
cluster center, projected distance from the nearest bright galaxy, and
projected local number density of galaxies are adopted as the
environmental parameters. The following results are obtained: (1) dE's
in the central region (r ≤ 5°) of the Virgo Cluster have larger
diameters and brighter magnitudes than those in the outer region (r ≥
5°). (2) The photometric parameters have no significant correlations
with either the distance from the nearest bright galaxy or the local
number density of galaxies. Implications of these results on the
scenarios of the formation and evolution of dE's are discussed.
The Astronomical Journal 06/1988; 96:62-72. · 4.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have developed a Java-based image browser system for the Subaru
telescope. The system will be used for a quick inspection of the
archived images from remote institutes and of the observed images at a
telescope operation room. The browser system supports functions to show
spectral traces, statistics, etc., as well as an image itself to help
users to easily evaluate the image quality. The browser system has been
developed to reduce network traffic between a server and clients. The
images, which are compressed for rapid transfer, are generated with care
for each observational instrument in order to minimize the loss of the
information.
172:413.
-
[show abstract]
[hide abstract]
ABSTRACT: Photographic surface photometry of NGC 1068 in B, V, and i bands is
carried out to obtain high-resolution two-dimensional luminosity and
color distributions. The inner two-component structure consisting of the
inner arm region of very high surface brightness and the main disk with
a shallow luminosity gradient is seen in the images of all the three
bands. This implies that the structure represents the distribution of
the underlying stellar component as well as that of the gaseous
component. Optical properties of the inner arm region and the main disk
and of the blue knots identified by Schild et al. (1985) are
investigated using the (B-V, V-i) two-color diagram. The inner arm
region is found to have systematically different colors from the main
disk. It is shown that the colors of the main disk are broadly
consistent with the population models of Arimoto and Yoshii (1986), but
the inner arm region is bluer in V-i and redder in B-V than the models.
The eight blue knots are found to be distributed in four different
regions on the diagram. The characteristics of these knots are
discussed.
Publications- Astronomical Society of Japan 39:411-424. · 2.44 Impact Factor
-
Hajime Baba,
Naoki Yasuda, Shin-Ichi Ichikawa,
Masafumi Yagi,
Nobuyuki Iwamoto,
Tadafumi Takata,
Toshihiro Horaguchi,
Masatoshi Taga,
Masaru Watanabe,
Tomohiko Ozawa,
Masaru Hamabe
[show abstract]
[hide abstract]
ABSTRACT: We have developed the Subaru-Mitaka-Okayama-Kiso-Archive (SMOKA) public
science archive system which provides access to the data of the Subaru
Telescope, the 188 cm telescope at Okayama Astrophysical Observatory,
and the 105 cm Schmidt telescope at Kiso Observatory/University of
Tokyo. SMOKA is the successor of the MOKA3 system.
The user can browse the Quick-Look Images, Header Information (HDI) and
the ASCII Table Extension (ATE) of each frame from the search result
table. A request for data can be submitted in a simple manner.
The system is developed with Java Servlet for the back-end, and Java
Server Pages (JSP) for content display. The advantage of JSP's is the
separation of the front-end presentation from the middle- and back-end
tiers which led to an efficient development of the system. The SMOKA
homepage is available at SMOKA
281:298.
-
Tokyo: University of Tokyo Press, 1990, edited by Kodaira, Keiichi; Okamura, Sadanori; Ichikawa, Shin-ichi. -1.
-
[show abstract]
[hide abstract]
ABSTRACT: Five Shakhbazyan compact groups of galaxies (SCGG 202, 205, 223, 245,
and 348) are studied. Their redshifts were found to be 0.027, 0.096,
0.083, 0.062, and 0.089, respectively. The galaxies are deficient in
population in the faint part of the luminosity function (Mv greater than
-20). The findings suggest that these SCGGs may be isolated physical
groups composed of about 10 bright members.
Publications of the National Astronomical Observatory of Japan. 1:283-295.
-
Chirs Stoughton,
Rpbert H. Lupton,
Mariangela Bernardi,
Michael R. Blanton,
Scott Burles,
Francsico J. Castander,
A. J. Connolly,
Daniel J. Eisenstein,
Johua A. Frieman,
G. S. Hennessy, [......],
Masaru Watanabe,
David H. Weinberg,
Richard L. White,
Simon D. M. White,
Brian Wilhite,
David Wolfe,
Naoki Yasuda,
Donald G. York,
Idit Zehavi,
Wei Zheng
[show abstract]
[hide abstract]
ABSTRACT: The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of 10 6 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg(2) of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux- and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Angstrom at R approximate to 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.
The Astronomical Journal, v.123, 485-548 (2002).
-
Jennifer K. Adelman-McCarthy,
Marcel A. Agüeros,
Sahar S. Allam,
Carlos Allende Prieto,
Kurt S. J. Anderson,
Scott F. Anderson,
James Annis,
Neta A. Bahcall,
C. A. L. Bailer-Jones,
Ivan K. Baldry, [......],
Yogesh Wadadekar,
David H. Weinberg,
Andrew A. West,
Simon D. M. White,
Brian C. Wilhite,
Brian Yanny,
D. R. Yocum,
Donald G. York,
Idit Zehavi,
Daniel B. Zucker
[show abstract]
[hide abstract]
ABSTRACT: This paper describes the Sixth Data Release of the Sloan Digital Sky Survey. With this data release, the imaging of the northern Galactic cap is now complete. The survey contains images and parameters of roughly 287 million objects over 9583 deg^2, including scans over a large range of Galactic latitudes and longitudes. The survey also includes 1.27 million spectra of stars, galaxies, quasars, and blank sky (for sky subtraction) selected over 7425 deg^2. This release includes much more stellar spectroscopy than was available in previous data releases and also includes detailed estimates of stellar temperatures, gravities, and metallicities. The results of improved photometric calibration are now available, with uncertainties of roughly 1% in g, r, i, and z, and 2% in u, substantially better than the uncertainties in previous data releases. The spectra in this data release have improved wavelength and flux calibration, especially in the extreme blue and extreme red, leading to the qualitatively better determination of stellar types and radial velocities. The spectrophotometric fluxes are now tied to point-spread function magnitudes of stars rather than fiber magnitudes. This gives more robust results in the presence of seeing variations, but also implies a change in the spectrophotometric scale, which is now brighter by roughly 0.35 mag. Systematic errors in the velocity dispersions of galaxies have been fixed, and the results of two independent codes for determining spectral classifications and redshifts are made available. Additional spectral outputs are made available, including calibrated spectra from individual 15 minute exposures and the sky spectrum subtracted from each exposure. We also quantify a recently recognized underestimation of the brightnesses of galaxies of large angular extent due to poor sky subtraction; the bias can exceed 0.2 mag for galaxies brighter than r = 14 mag.
-
Kevork N. Abazajian,
Jennifer K. Adelman-McCarthy,
Marcel A. Agüeros,
Sahar S. Allam,
Carlos Allende Prieto,
Deokkeun An,
Kurt S. J. Anderson,
Scott F. Anderson,
James Annis,
Neta A. Bahcall, [......],
Andrew A. West,
Simon D. M. White,
Brian C. Wilhite,
Alainna C. Wonders,
Brian Yanny,
D. R. Yocum,
Donald G. York,
Idit Zehavi,
Stefano Zibetti,
Daniel B. Zucker
[show abstract]
[hide abstract]
ABSTRACT: This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11,663 deg^2 of imaging data, with most of the ~2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry on a 120° long, 2°.5 wide stripe along the celestial equator in the Southern Galactic Cap, with some regions covered by as many as 90 individual imaging runs. We include a co-addition of the best of these data, going roughly 2 mag fainter than the main survey over 250 deg^2. The survey has completed spectroscopy over 9380 deg^2; the spectroscopy is now complete over a large contiguous area of the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog, reducing the rms statistical errors at the bright end to 45 milliarcseconds per coordinate. We further quantify a systematic error in bright galaxy photometry due to poor sky determination; this problem is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.
