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SDSS-III Collaboration: Christopher P. Ahn,
Rachael Alexandroff,
Carlos Allende Prieto,
Scott F. Anderson,
Timothy Anderton,
Brett H. Andrews,
Éric Aubourg Stephen Bailey,
Rory Barnes,
Julian Bautista,
Timothy C. Beers, [......],
Brian Yanny,
Christophe Yèche,
Donald G. York,
O. Zamora,
Gail Zasowski,
Idit Zehavi,
Gong-Bo Zhao,
Zheng Zheng,
Guangtun Zhu,
Joel C. Zinn
[show abstract]
[hide abstract]
ABSTRACT: The Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic
data from the Baryon Oscillation Spectroscopic Survey (BOSS). This ninth data
release (DR9) of the SDSS project includes 535,995 new galaxy spectra (median
z=0.52), 102,100 new quasar spectra (median z=2.32), and 90,897 new stellar
spectra, along with the data presented in previous data releases. These spectra
were obtained with the new BOSS spectrograph and were taken between 2009
December and 2011 July. In addition, the stellar parameters pipeline, which
determines radial velocities, surface temperatures, surface gravities, and
metallicities of stars, has been updated and refined with improvements in
temperature estimates for stars with T_eff<5000 K and in metallicity estimates
for stars with [Fe/H]>-0.5. DR9 includes new stellar parameters for all stars
presented in DR8, including stars from SDSS-I and II, as well as those observed
as part of the SDSS-III Sloan Extension for Galactic Understanding and
Exploration-2 (SEGUE-2).
The astrometry error introduced in the DR8 imaging catalogs has been
corrected in the DR9 data products. The next data release for SDSS-III will be
in Summer 2013, which will present the first data from the Apache Point
Observatory Galactic Evolution Experiment (APOGEE) along with another year of
data from BOSS, followed by the final SDSS-III data release in December 2014.
07/2012;
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Timothy C. Beers,
Daniela Carollo,
Željko Ivezić,
Deokkeun An,
Masashi Chiba,
John E. Norris,
Ken C. Freeman,
Young Sun Lee, Jeffrey A. Munn,
Paola Re Fiorentin,
Thirupathi Sivarani,
Ronald Wilhelm,
Brian Yanny,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: Carollo et al. have recently resolved the stellar population of the Milky Way halo into at least two distinct components, an inner halo and an outer halo. This result has been criticized by Schönrich et al., who claim that the retrograde signature associated with the outer halo is due to the adoption of faulty distances. We refute this claim, and demonstrate that the Schönrich et al. photometric distances are themselves flawed because they adopted an incorrect main-sequence absolute magnitude relationship from the work of Ivezić et al. When compared to the recommended relation from Ivezić et al., which is tied to a Milky Way globular cluster distance scale and accounts for age and metallicity effects, the relation adopted by Schönrich et al. yields up to 18% shorter distances for stars near the main-sequence turnoff (TO). Use of the correct relationship yields agreement between the distances assigned by Carollo et al. and Ivezić et al. for low-metallicity dwarfs to within 6%-10%. Schönrich et al. also point out that intermediate-gravity stars (3.5 ≤log g < 4.0) with colors redder than the TO region are likely misclassified, with which we concur. We implement a new procedure to reassign luminosity classifications for the TO stars that require it. New derivations of the rotational behavior demonstrate that the retrograde signature and high velocity dispersion of the outer-halo population remain. We summarize additional lines of evidence for a dual halo, including a test of the retrograde signature based on proper motions alone, and conclude that the preponderance of evidence strongly rejects the single-halo interpretation.
The Astrophysical Journal 01/2012; 746(1):34. · 6.02 Impact Factor
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SDSS-III collaboration: Hiroaki Aihara,
Carlos Allende Prieto,
Deokkeun An,
Scott F. Anderson,
Éric Aubourg,
Eduardo Balbinot,
Timothy C. Beers,
Andreas A. Berlind,
Steven J. Bickerton,
Dmitry Bizyaev, [......],
David A. Wake,
Ji Wang,
Benjamin A. Weaver,
David H. Weinberg,
Martin White,
Simon D. M. White,
Brian Yanny,
Naoki Yasuda,
Christophe Yeche,
Idit Zehavi
[show abstract]
[hide abstract]
ABSTRACT: The Sloan Digital Sky Survey (SDSS) started a new phase in August 2008, with
new instrumentation and new surveys focused on Galactic structure and chemical
evolution, measurements of the baryon oscillation feature in the clustering of
galaxies and the quasar Ly alpha forest, and a radial velocity search for
planets around ~8000 stars. This paper describes the first data release of
SDSS-III (and the eighth counting from the beginning of the SDSS). The release
includes five-band imaging of roughly 5200 deg^2 in the Southern Galactic Cap,
bringing the total footprint of the SDSS imaging to 14,555 deg^2, or over a
third of the Celestial Sphere. All the imaging data have been reprocessed with
an improved sky-subtraction algorithm and a final, self-consistent photometric
recalibration and flat-field determination. This release also includes all data
from the second phase of the Sloan Extension for Galactic Understanding and
Evolution (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars
at both high and low Galactic latitudes. All the more than half a million
stellar spectra obtained with the SDSS spectrograph have been reprocessed
through an improved stellar parameters pipeline, which has better determination
of metallicity for high metallicity stars.
01/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We present optical spectroscopy and near-infrared photometry of 126 cool white dwarfs (WDs) in the Sloan Digital Sky Survey (SDSS). Our sample includes high proper motion targets selected using the SDSS and USNO-B astrometry and a dozen previously known ultracool WD candidates. Our optical spectroscopic observations demonstrate that a clean selection of large samples of cool WDs in the SDSS (and the SkyMapper, Pan-STARRS, and the Large Synoptic Survey Telescope data sets) is possible using a reduced proper motion diagram and a tangential velocity cut-off (depending on the proper motion accuracy) of 30 km s–1. Our near-infrared observations reveal eight new stars with significant absorption. We use the optical and near-infrared photometry to perform a detailed model atmosphere analysis. More than 80% of the stars in our sample are consistent with either pure hydrogen or pure helium atmospheres. However, the eight stars with significant infrared absorption and the majority of the previously known ultracool WD candidates are best explained with mixed hydrogen and helium atmosphere models. The age distribution of our sample is consistent with a Galactic disk age of 8 Gyr. A few ultracool WDs may be as old as 12-13 Gyr, but our models have problems matching the spectral energy distributions of these objects. There are only two halo WD candidates in our sample. However, trigonometric parallax observations are required for accurate mass and age determinations and to confirm their membership in the halo.
The Astrophysical Journal Supplement Series 08/2010; 190(1):77. · 13.46 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of three nearby old halo white dwarf (WD) candidates in the Sloan Digital Sky Survey (SDSS), including two stars in a common proper motion binary system. These candidates are selected from our 2800deg2 proper motion survey on the Bok and U.S. Naval Observatory Flagstaff Station 1.3 m telescopes, and they display proper motions of 04-05 yr–1. Follow-up MMT spectroscopy and near-infrared photometry demonstrate that all three objects are hydrogen-dominated atmosphere WDs with T eff 3700-4100 K. For average mass WDs, these temperature estimates correspond to cooling ages of 9-10 Gyr, distances of 70-80 pc, and tangential velocities of 140-200 km s–1. Based on the UVW space velocities, we conclude that they most likely belong to the halo. Furthermore, the combined main-sequence and WD cooling ages are 10-11 Gyr. Along with SDSS J1102+4113, they are the oldest field WDs currently known. These three stars represent only a small fraction of the halo WD candidates in our proper motion survey, and they demonstrate that deep imaging surveys like the Pan-STARRS and Large Synoptic Survey Telescope should find many old thick disk and halo WDs that can be used to constrain the age of the Galactic thick disk and halo.
The Astrophysical Journal Letters 04/2010; 715(1):L21. · 5.53 Impact Factor
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[show abstract]
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ABSTRACT: Redshifts, four-band photometry (UBJRFIN), and astrometry are presented for faint galaxies in four widely separated fields. We provide the necessary information to enable well-defined, statistically complete subsamples of faint galaxies to be constructed from the master catalog. The redshift survey is 86% and 71% complete to RF ≤ 18.5 and RF ≤ 19, respectively, yielding 328 galaxies with reliable redshifts to RF ≤ 19, with a median redshift of 0.142. Adding the galaxies from the fainter statistical sample yields a total of 583 reliable redshifts with a median redshift of 0.202. An additional 156 redshifts in the same fields, but not part of the samples defined here, are also given. Of the 739 galaxy redshifts presented, 212 are for galaxies with RF > 20.
The Astrophysical Journal Supplement Series 01/2009; 109(1):45. · 13.46 Impact Factor
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Gordon T. Richards,
Robert C. Nichol,
Alexander G. Gray,
Robert J. Brunner,
Robert H. Lupton,
Daniel E. Vanden Berk,
Shang Shan Chong,
Michael A. Weinstein,
Donald P. Schneider,
Scott F. Anderson, Jeffrey A. Munn,
Hugh C. Harris,
Michael A. Strauss,
Xiaohui Fan,
James E. Gunn,
Željko Ivezić,
Donald G. York,
J. Brinkmann,
and Andrew W. Moore
[show abstract]
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ABSTRACT: We present a catalog of 100,563 unresolved, UV-excess (UVX) quasar candidates to g = 21 from 2099 deg2 of the Sloan Digital Sky Survey (SDSS) Data Release One (DR1) imaging data. Existing spectra of 22,737 sources reveals that 22,191 (97.6%) are quasars; accounting for the magnitude dependence of this efficiency, we estimate that 95,502 (95.0%) of the objects in the catalog are quasars. Such a high efficiency is unprecedented in broadband surveys of quasars. This "proof-of-concept" sample is designed to be maximally efficient, but still has 94.7% completeness to unresolved, g 19.5, UVX quasars from the DR1 quasar catalog. This efficient and complete selection is the result of our application of a probability density type analysis to training sets that describe the four-dimensional color distribution of stars and spectroscopically confirmed quasars in the SDSS. Specifically, we use a nonparametric Bayesian classification, based on kernel density estimation, to parameterize the color distribution of astronomical sources—allowing for fast and robust classification. We further supplement the catalog by providing photometric redshifts and matches to FIRST/VLA, ROSAT, and USNO-B sources. Future work needed to extend this selection algorithm to larger redshifts, fainter magnitudes, and resolved sources is discussed. Finally, we examine some science applications of the catalog, particularly a tentative quasar number counts distribution covering the largest range in magnitude (14.2 < g < 21.0) ever made within the framework of a single quasar survey.
The Astrophysical Journal Supplement Series 12/2008; 155(2):257. · 13.46 Impact Factor
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Zlatan I. Tsvetanov,
David A. Golimowski,
Wei Zheng,
T. R. Geballe,
S. K. Leggett,
Holland C. Ford,
Arthur F. Davidsen,
Alan Uomoto,
Xiaohui Fan,
G. R. Knapp, [......],
Donald G. York,
Robert H. Lupton,
Jeffrey R. Pier,
James Annis,
István Csabai,
Robert B. Hindsley,
Željko Ivesić, Jeffrey A. Munn,
Aniruddha R. Thakar,
and Patrick Waddell
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of a second field methane brown dwarf from the commissioning data of the Sloan Digital Sky Survey (SDSS). The object, SDSS J134646.45-003150.4 (hereafter SDSS 1346-00), was selected because of its very red color and stellar appearance. Its spectrum between 0.8 and 2.5 μm is dominated by strong absorption bands of H2O and CH4 and closely mimics those of Gliese 229B and SDSS 162414.37+002915.6 (hereafter SDSS 1624+00), two other known methane brown dwarfs. SDSS 1346-00 is approximately 1.5 mag fainter than Gliese 229B, suggesting that it lies about 11 pc from the Sun. The ratio of flux at 2.1 μm to that at 1.27 μm is larger for SDSS 1346-00 than for Gliese 229B and SDSS 1624+00, which suggests that SDSS 1346-00 has a slightly higher effective temperature than the others. Based on a search area of 130 deg2 and a detection limit of z* = 19.8, we estimate a space density of 0.05 pc-3 for methane brown dwarfs with Teff ~ 1000 K in the 40 pc3 volume of our search. This estimate is based on small-sample statistics and should be treated with appropriate caution.
The Astrophysical Journal 12/2008; 531(1):L61. · 6.02 Impact Factor
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Erin Scott Sheldon,
James Annis,
Hans Böhringer,
Philippe Fischer,
Joshua A. Frieman,
Michael Joffre,
David Johnston,
Timothy A. McKay,
Christopher Miller,
R. C. Nichol, [......],
J. Brinkmann,
Robert Brunner,
István Csabai,
Masataka Fukugita,
G. S. Hennessy,
Željko Ivezić,
Robert H. Lupton, Jeffrey A. Munn,
Jeffrey R. Pier,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We present a lensing study of 42 galaxy clusters imaged in Sloan Digital Sky Survey (SDSS) commissioning data. Cluster candidates are selected optically from SDSS imaging data and confirmed for this study by matching to X-ray sources found independently in the ROSAT All-Sky Survey (RASS). Five-color SDSS photometry is used to make accurate (Δz = 0.018) photometric redshift estimates that are used to rescale and combine the lensing measurements. The mean shear from these clusters is detected to 2 h-1 Mpc at the 7 σ level, corresponding to a mass within that radius of (4.2 ± 0.6) × 1014 h-1 M☉. The shear profile is well fitted by a power law with index -0.9 ± 0.3, consistent with that of an isothermal density profile. Clusters are divided by X-ray luminosity into two subsets, with mean LX of (0.14 ± 0.03) × 1044 and (1.0 ± 0.09) × 1044 h-2 ergs s-1. The average lensing signal is converted to a projected mass density based on fits to isothermal density profiles. From this we calculate a mean r500 (the radius at which the mean density falls to 500 times the critical density) and M(<r500). The mass contained within r500 differs substantially between the low- and high-LX bins, with (0.7 ± 0.2) × 1014 and 2.7×1014 h-1 M☉, respectively. This paper demonstrates our ability to measure ensemble cluster masses from SDSS imaging data. The full SDSS data set will include 1000 SDSS/RASS clusters. With this large data set we will measure the M-LX relation with high precision and put direct constraints on the mass density of the universe.
The Astrophysical Journal 12/2008; 554(2):881. · 6.02 Impact Factor
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Scott Dodelson,
Vijay K. Narayanan,
Max Tegmark,
Ryan Scranton,
Tamas Budavári,
Andrew Connolly,
Istvan Csabai,
Daniel Eisenstein,
Joshua A. Frieman,
James E. Gunn, [......], Jeffrey A. Munn,
John Peoples,
Jeffrey R. Pier,
Constance Rockosi,
David Schlegel,
Christopher Stoughton,
Douglas L. Tucker,
Brian Yanny,
Donald G. York,
and (for the SDSS Collaboration
[show abstract]
[hide abstract]
ABSTRACT: Early photometric data from the Sloan Digital Sky Survey (SDSS) contain angular positions for 1.5 million galaxies. In companion papers, the angular correlation function w(θ) and two-dimensional power spectrum Cl of these galaxies are presented. Here we invert Limber's equation to extract the three-dimensional power spectrum from the angular results. We accomplish this using an estimate of dn/dz, the redshift distribution of galaxies in four different magnitude slices in the SDSS photometric catalog. The resulting three-dimensional power spectrum estimates from w(θ) and Cl agree with each other and with previous estimates over a range in wavenumbers 0.03 < k/(h Mpc-1) < 1. The galaxies in the faintest magnitude bin (21 < r* < 22, which have median redshift zm = 0.43) are less clustered than the galaxies in the brightest magnitude bin (18 < r* < 19 with zm = 0.17), especially on scales where nonlinearities are important. The derived power spectrum agrees with that of Szalay et al., who go directly from the raw data to a parametric estimate of the power spectrum. The strongest constraints on the shape parameter Γ come from the faintest galaxies (in the magnitude bin 21 < r* < 22), from which we infer Γ = 0.14 (95% CL).
The Astrophysical Journal 12/2008; 572(1):140. · 6.02 Impact Factor
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Michael R. Blanton,
David W. Hogg,
Neta A. Bahcall,
Ivan K. Baldry,
J. Brinkmann,
István Csabai,
Daniel Eisenstein,
Masataka Fukugita,
James E. Gunn,
Željko Ivezić, [......],
Robert H. Lupton,
Jon Loveday, Jeffrey A. Munn,
R. C. Nichol,
Sadanori Okamura,
David J. Schlegel,
Kazuhiro Shimasaku,
Michael A. Strauss,
Michael S. Vogeley,
and David H. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: Using photometry and spectroscopy of 183,487 galaxies from the Sloan Digital Sky Survey, we present bivariate distributions of pairs of seven galaxy properties: four optical colors, surface brightness, radial profile shape as measured by the Sérsic index, and absolute magnitude. In addition, we present the dependence of local galaxy density (smoothed on 8 h-1 Mpc scales) on all of these properties. Several classic, well-known relations among galaxy properties are evident at extremely high signal-to-noise ratio: the color-color relations of galaxies, the color-magnitude relations, the magnitude-surface brightness relation, and the dependence of density on color and absolute magnitude. We show that most of the i-band luminosity density in the universe is in the absolute magnitude and surface brightness ranges used: -23.5 < M < -17.0 mag and 17 < μ < 24 mag in 1 arcsec2 [the notation zb represents the b band shifted blueward by a factor (1 + z)]. Some of the relationships between parameters, in particular the color-magnitude relations, show stronger correlations for exponential galaxies and concentrated galaxies taken separately than for all galaxies taken together. We provide a simple set of fits of the dependence of galaxy properties on luminosity for these two sets of galaxies and other quantitative details of our results.
The Astrophysical Journal 12/2008; 594(1):186. · 6.02 Impact Factor
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Michael Odenkirchen,
Eva K. Grebel,
Constance M. Rockosi,
Walter Dehnen,
Rodrigo Ibata,
Hans-Walter Rix,
Andrea Stolte,
Christian Wolf,
John E. Anderson,
Jr, [......],
Jon Brinkmann,
István Csabai,
G. Hennessy,
Robert B. Hindsley,
Željko Ivezić,
Robert H. Lupton, Jeffrey A. Munn,
Jeffrey R. Pier,
Chris Stoughton,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of two well-defined tidal tails emerging from the sparse remote globular cluster Palomar 5. These tails stretch out symmetrically to both sides of the cluster in the direction of constant Galactic latitude and subtend an angle of 26 on the sky. The tails have been detected in commissioning data of the Sloan Digital Sky Survey, providing deep five-color photometry in a 25-wide band along the equator. The stars in the tails make up a substantial part (~) of the current total population of cluster stars in the magnitude interval 19.5 ≤ i* ≤ 22.0. This reveals that the cluster is subject to heavy mass loss. The orientation of the tails provides an important key for the determination of the cluster's Galactic orbit.
The Astrophysical Journal 12/2008; 548(2):L165. · 6.02 Impact Factor
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Michael R. Blanton,
David W. Hogg,
Neta A. Bahcall,
J. Brinkmann,
Malcolm Britton,
Andrew J. Connolly,
István Csabai,
Masataka Fukugita,
Jon Loveday,
Avery Meiksin, Jeffrey A. Munn,
R. C. Nichol,
Sadanori Okamura,
Thomas Quinn,
Donald P. Schneider,
Kazuhiro Shimasaku,
Michael A. Strauss,
Max Tegmark,
Michael S. Vogeley,
and David H. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: Using a catalog of 147,986 galaxy redshifts and fluxes from the Sloan Digital Sky Survey (SDSS), we measure the galaxy luminosity density at z = 0.1 in five optical bandpasses corresponding to the SDSS bandpasses shifted to match their rest-frame shape at z = 0.1. We denote the bands 0.1u, 0.1g, 0.1r, 0.1i, 0.1z with λeff = (3216, 4240, 5595, 6792, 8111 Å), respectively. To estimate the luminosity function, we use a maximum likelihood method that allows for a general form for the shape of the luminosity function, fits for simple luminosity and number evolution, incorporates the flux uncertainties, and accounts for the flux limits of the survey. We find luminosity densities at z = 0.1 expressed in absolute AB magnitudes in a Mpc3 to be (-14.10 ± 0.15, -15.18 ± 0.03, -15.90 ± 0.03, -16.24 ± 0.03, -16.56 ± 0.02) in (0.1u, 0.1g, 0.1r, 0.1i, 0.1z), respectively, for a cosmological model with Ω0 = 0.3, ΩΛ = 0.7, and h = 1 and using SDSS Petrosian magnitudes. Similar results are obtained using Sérsic model magnitudes, suggesting that flux from outside the Petrosian apertures is not a major correction. In the 0.1r band, the best-fit Schechter function to our results has * = (1.49 ± 0.04) × 10-2 h3 Mpc-3, M* - 5 log10 h = -20.44 ± 0.01, and α = -1.05 ± 0.01. In solar luminosities, the luminosity density in 0.1r is (1.84 ± 0.04) × 108 h L0.1r,☉ Mpc-3. Our results in the 0.1g band are consistent with other estimates of the luminosity density, from the Two-Degree Field Galaxy Redshift Survey and the Millennium Galaxy Catalog. They represent a substantial change (~0.5 mag) from earlier SDSS luminosity density results based on commissioning data, almost entirely because of the inclusion of evolution in the luminosity function model.
The Astrophysical Journal 12/2008; 592(2):819. · 6.02 Impact Factor
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Hugh C. Harris,
Evalyn Gates,
Geza Gyuk,
Mark Subbarao,
Scott F. Anderson,
Patrick B. Hall, Jeffrey A. Munn,
James Liebert,
Gillian R. Knapp,
D. Bizyaev,
E. Malanushenko,
V. Malanushenko,
K. Pan,
Donald P. Schneider,
and J. Allyn Smith
[show abstract]
[hide abstract]
ABSTRACT: We identify seven new ultracool white dwarfs discovered in the Sloan Digital Sky Survey (SDSS). The SDSS photometry, spectra, and proper motions are presented, and additional BVRI data are given for these and other previously discovered ultracool white dwarfs. The observed colors span a remarkably wide range, qualitatively similar to colors predicted by models for very cool white dwarfs. One of the new stars (SDSS J1251+44) exhibits strong collision-induced absorption (CIA) in its spectra, while the spectra and colors of the other six are consistent with mild CIA. Another of the new discoveries (SDSS J2239+00A) is part of a binary system—its companion is also a cool white dwarf, and other data indicate that the companion exhibits an infrared flux deficiency, making this the first binary system composed of two CIA white dwarfs. A third discovery (SDSS J0310–00) has weak Balmer emission lines. The proper motions of all seven stars are consistent with membership in the disk or thick disk.
The Astrophysical Journal 12/2008; 679(1):697. · 6.02 Impact Factor
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Daniel J. Eisenstein,
David W. Hogg,
Masataka Fukugita,
Osamu Nakamura,
Mariangela Bernardi,
Douglas P. Finkbeiner,
David J. Schlegel,
J. Brinkmann,
Andrew J. Connolly,
István Csabai,
James E. Gunn,
Željko Ivezić,
Don Q. Lamb,
Jon Loveday, Jeffrey A. Munn,
Robert C. Nichol,
Donald P. Schneider,
Michael A. Strauss,
Alex Szalay,
and Don G. York
[show abstract]
[hide abstract]
ABSTRACT: We combine Sloan Digital Sky Survey spectra of 22,000 luminous, red, bulge-dominated galaxies to get high signal-to-noise ratio average spectra in the rest-frame optical and ultraviolet (2600-7000 Å). The average spectra of these massive, quiescent galaxies are early type with weak emission lines and with absorption lines indicating an apparent excess of α-elements over solar abundance ratios. We make average spectra of subsamples selected by luminosity, environment, and redshift. The average spectra are remarkable in their similarity. What variations do exist in the average spectra as a function of luminosity and environment are found to form a nearly one-parameter family in spectrum space. We present a high signal-to-noise ratio spectrum of the variation. We measure the properties of the variation with a modified version of the Lick index system and compare to model spectra from stellar population syntheses. The variation may be a combination of age and chemical abundance differences, but the conservative conclusion is that the quality of the data considerably exceeds the current state of the models.
The Astrophysical Journal 12/2008; 585(2):694. · 6.02 Impact Factor
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Bing Chen,
Chris Stoughton,
J. Allyn Smith,
Alan Uomoto,
Jeffrey R. Pier,
Brian Yanny,
Željko Ivezić,
Donald G. York,
John E. Anderson,
James Annis,
Jon Brinkmann,
István Csabai,
Masataka Fukugita,
Robert Hindsley,
Robert Lupton, Jeffrey A. Munn,
and for the SDSS Collaboration
[show abstract]
[hide abstract]
ABSTRACT: We present star count data from the Sloan Digital Sky Survey for 5.8 × 105 stars brighter than g' = 21 mag over 279 deg2 in two samples north and south of the Galactic plane. Using these high-latitude (49° < |b| < 64°) star counts we determine the Sun's distance from the Galactic midplane to be 27 ± 4 pc and the scale height of the old thin disk to be 330 ± 3 pc. Because of the photometric accuracy and large area sky coverage of these data, the color-magnitude diagram clearly reveals a significant thick-disk population distinct in color from a Galactic halo population. The position of the thick-disk turnoff is at g'-r' ~ 0.33. Several questions about the existence of the thick disk and its origin are addressed through a set of model fits to the star count data. Our best-fit model gives a thick-disk scale height between 580 and 750 pc, below the original proposal of Gilmore and Reid, and the corresponding space number density normalization is 13%-6.5% of the thin disk. The conclusions reached in this paper favor a scenario in which the thick disk formed through the heating of a preexisting thin disk, with the heating mechanism being the merging of a satellite galaxy. The density law for the Galactic halo population is also investigated. We find that the data support a flattened halo with c/a ~ 0.55 ± 0.06 and a relatively flat power-law index (2.5 ± 0.3). The axis ratio of the visible halo found in this paper is compatible with that of dark halo, suggesting that they have the same shape and dynamical origin.
The Astrophysical Journal 12/2008; 553(1):184. · 6.02 Impact Factor
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S. J. Kleinman,
Hugh C. Harris,
Daniel J. Eisenstein,
James Liebert,
Atsuko Nitta,
Jurek Krzesiński, Jeffrey A. Munn,
Conard C. Dahn,
Suzanne L. Hawley,
Jeffrey R. Pier, [......],
Matthew J. Collinge,
A. S. Mukadam,
D. Koester,
Alan Uomoto,
D. J. Schlegel,
Scott F. Anderson,
J. Brinkmann,
D. Q. Lamb,
Donald P. Schneider,
and Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We present the full spectroscopic white dwarf and hot subdwarf sample from the Sloan Digital Sky Survey (SDSS) first data release, DR1. We find 2551 white dwarf stars of various types, 240 hot subdwarf stars, and an additional 144 objects we have identified as uncertain white dwarf stars. Of the white dwarf stars, 1888 are nonmagnetic DA types and 171 are nonmagnetic DBs. The remaining (492) objects consist of all different types of white dwarf stars: DO, DQ, DC, DH, DZ, hybrid stars such as DAB, etc., and those with nondegenerate companions. We fit the DA and DB spectra with a grid of models to determine the Teff and log g for each object. For all objects, we provide coordinates, proper motions, SDSS photometric magnitudes, and enough information to retrieve the spectrum/image from the SDSS public database. This catalog nearly doubles the known sample of spectroscopically identified white dwarf stars. In the DR1 imaged area of the sky, we increase the known sample of white dwarf stars by a factor of 8.5. We also comment on several particularly interesting objects in this sample.
The Astrophysical Journal 12/2008; 607(1):426. · 6.02 Impact Factor
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Max Tegmark,
Scott Dodelson,
Daniel J. Eisenstein,
Vijay Narayanan,
Roman Scoccimarro,
Ryan Scranton,
Michael A. Strauss,
Andrew Connolly,
Joshua A. Frieman,
James E. Gunn, [......], Jeffrey A. Munn,
John Peoples,
Jeffrey R. Pier,
Michael Richmond,
Constance Rockosi,
David Schlegel,
Christopher Stoughton,
Douglas L. Tucker,
Brian Yanny,
Donald G. York
[show abstract]
[hide abstract]
ABSTRACT: We compute the angular power spectrum Cl from 1.5 million galaxies in early Sloan Digital Sky Survey (SDSS) data on large angular scales, l 600. The data set covers about 160 deg2, with a characteristic depth on the order of 1 h-1 Gpc in the faintest (21 < r* < 22) of our four magnitude bins. Cosmological interpretations of these results are presented in a companion paper by Dodelson and coworkers. The data in all four magnitude bins are consistent with a simple flat "concordance" model with nonlinear evolution and linear bias factors on the order of unity. Nonlinear evolution is particularly evident for the brightest galaxies. A series of tests suggests that systematic errors related to seeing, reddening, etc. are negligible, which bodes well for the 60-fold larger sample that the SDSS is currently collecting. Uncorrelated error bars and well-behaved window functions make our measurements a convenient starting point for cosmological model fitting.
The Astrophysical Journal 12/2008; 571(1):191. · 6.02 Impact Factor
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Gary D. Schmidt,
Hugh C. Harris,
James Liebert,
Daniel J. Eisenstein,
Scott F. Anderson,
J. Brinkmann,
Patrick B. Hall,
Michael Harvanek,
Suzanne Hawley,
S. J. Kleinman, [......],
Eric H. Neilsen,
Peter R. Newman,
Atsuko Nitta,
David J. Schlegel,
Donald P. Schneider,
Nicole M. Silvestri,
J. Allyn Smith,
Stephanie A. Snedden,
Paula Szkody,
and Dan Vanden Berk
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ABSTRACT: Beyond its goals related to the extragalactic universe, the Sloan Digital Sky Survey (SDSS) is an effective tool for identifying stellar objects with unusual spectral energy distributions. Here we report on the 53 new magnetic white dwarfs discovered during the first two years of the survey, including 38 whose data are made public in the 1500 deg2 First Data Release. Discoveries span the magnitude range 16.3 ≤ g ≤ 20.5, and based on the recovery rate for previously known magnetic white dwarfs, the completeness of the SDSS appears to be high for reasonably hot stars with B 3 MG and g 15. The new objects nearly double the total number of known magnetic white dwarfs and include examples with polar field strengths Bp > 500 MG, as well as several with exotic atmospheric compositions. The improved sample statistics and uniformity indicate that the distribution of magnetic white dwarfs has a broad peak in the range ~5-30 MG and a tail extending to nearly 109 G. Degenerates with polar fields Bp 50 MG are consistent with being descendents of magnetic Ap/Bp main-sequence stars, but low- and moderate-field magnetic white dwarfs appear to imply another origin. Yet-undetected magnetic F-type stars with convective envelopes that destroy the ordered underlying field are attractive candidates.
The Astrophysical Journal 12/2008; 595(2):1101. · 6.02 Impact Factor
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Idit Zehavi,
Michael R. Blanton,
Joshua A. Frieman,
David H. Weinberg,
Houjun J. Mo,
Michael A. Strauss,
Scott F. Anderson,
James Annis,
Neta A. Bahcall,
Mariangela Bernardi, [......],
Alexander S. Szalay,
Istvan Szapudi,
Max Tegmark,
Douglas L. Tucker,
Alan Uomoto,
Dan Vanden Berk,
Michael S. Vogeley,
Patrick Waddell,
Brian Yanny,
Donald G. York
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ABSTRACT: We present the first measurements of clustering in the Sloan Digital Sky Survey (SDSS) galaxy redshift survey. Our sample consists of 29,300 galaxies with redshifts 5700 km s-1 ≤ cz ≤ 39,000 km s-1, distributed in several long but narrow (25-5°) segments, covering 690 deg2. For the full, flux-limited sample, the redshift-space correlation length is approximately 8 h-1 Mpc. The two-dimensional correlation function ξ(rp,π) shows clear signatures of both the small-scale, "fingers-of-God" distortion caused by velocity dispersions in collapsed objects and the large-scale compression caused by coherent flows, though the latter cannot be measured with high precision in the present sample. The inferred real-space correlation function is well described by a power law, ξ(r) = (r/6.1 ± 0.2 h-1 Mpc)-1.75±0.03, for 0.1 h-1 Mpc ≤ r ≤ 16 h-1 Mpc. The galaxy pairwise velocity dispersion is σ12 ≈ 600 ± 100 km s-1 for projected separations 0.15 h-1 Mpc ≤ rp ≤ 5 h-1 Mpc. When we divide the sample by color, the red galaxies exhibit a stronger and steeper real-space correlation function and a higher pairwise velocity dispersion than do the blue galaxies. The relative behavior of subsamples defined by high/low profile concentration or high/low surface brightness is qualitatively similar to that of the red/blue subsamples. Our most striking result is a clear measurement of scale-independent luminosity bias at r 10 h-1 Mpc: subsamples with absolute magnitude ranges centered on M* - 1.5, M*, and M* + 1.5 have real-space correlation functions that are parallel power laws of slope ≈-1.8 with correlation lengths of approximately 7.4, 6.3, and 4.7 h-1 Mpc, respectively.
The Astrophysical Journal 12/2008; 571(1):172. · 6.02 Impact Factor
