318 research outputs found
The Apache Point Observatory Galactic Evolution Experiment: First Detection of High Velocity Milky Way Bar Stars
Commissioning observations with the Apache Point Observatory Galactic
Evolution Experiment (APOGEE), part of the Sloan Digital Sky Survey III, have
produced radial velocities (RVs) for ~4700 K/M-giant stars in the Milky Way
bulge. These high-resolution (R \sim 22,500), high-S/N (>100 per resolution
element), near-infrared (1.51-1.70 um; NIR) spectra provide accurate RVs
(epsilon_v~0.2 km/s) for the sample of stars in 18 Galactic bulge fields
spanning -1-32 deg. This represents the largest
NIR high-resolution spectroscopic sample of giant stars ever assembled in this
region of the Galaxy. A cold (sigma_v~30 km/s), high-velocity peak (V_GSR \sim
+200 km/s) is found to comprise a significant fraction (~10%) of stars in many
of these fields. These high RVs have not been detected in previous MW surveys
and are not expected for a simple, circularly rotating disk. Preliminary
distance estimates rule out an origin from the background Sagittarius tidal
stream or a new stream in the MW disk. Comparison to various Galactic models
suggests that these high RVs are best explained by stars in orbits of the
Galactic bar potential, although some observational features remain
unexplained.Comment: 7 pages, 4 figures, accepted for publication in ApJ Letter
Faint High Latitude Carbon Stars Discovered by the Sloan Digital Sky Survey: Methods and Initial Results
We report the discovery of 39 Faint High Latitude Carbon Stars (FHLCs) from
Sloan Digital Sky Survey commissioning data. The objects, each selected
photometrically and verified spectroscopically, range over 16.6 < r* < 20.0,
and show a diversity of temperatures as judged by both colors and NaD line
strengths. At the completion of the Sloan Survey, there will be many hundred
homogeneously selected and observed FHLCs in this sample. We present proper
motion measures for each object, indicating that the sample is a mixture of
extremely distant (>100 kpc) halo giant stars, useful for constraining halo
dynamics, plus members of the recently-recognized exotic class of very nearby
dwarf carbon (dC) stars. Motions, and thus dC classification, are inferred for
40-50 percent of the sample, depending on the level of statistical significance
invoked. The new list of dC stars presented here, although selected from only a
small fraction of the final SDSS, doubles the number of such objects found by
all previous methods. (Abstract abridged).Comment: Accepted for publication in The Astronomical Journal, Vol. 124, Sep.
2002, 40 pages, 7 figures, AASTeX v5.
The New Generation Atlas of Quasar Spectral Energy Distributions from Radio to X-rays
We have produced the next generation of quasar spectral energy distributions
(SEDs), essentially updating the work of Elvis et al. (1994) by using
high-quality data obtained with several space and ground-based telescopes,
including NASA's Great Observatories. We present an atlas of SEDs of 85
optically bright, non-blazar quasars over the electromagnetic spectrum from
radio to X-rays. The heterogeneous sample includes 27 radio-quiet and 58
radio-loud quasars. Most objects have quasi-simultaneous ultraviolet-optical
spectroscopic data, supplemented with some far-ultraviolet spectra, and more
than half also have Spitzer mid-infrared IRS spectra. The X-ray spectral
parameters are collected from the literature where available. The radio,
far-infrared, and near-infrared photometric data are also obtained from either
the literature or new observations. We construct composite spectral energy
distributions for radio-loud and radio-quiet objects and compare these to those
of Elvis et al., finding that ours have similar overall shapes, but our
improved spectral resolution reveals more detailed features, especially in the
mid and near-infrared.Comment: 46 pages, 10 figures, 10 tables, Accepted by ApJS. Composite SED data
files for radio-loud and radio-quiet quasars (rlmsedMR.txt, rqmsedMR.txt) are
included in the source (Other formats -> Source). Supplemental figures are
not include
Ameliorating Systematic Uncertainties in the Angular Clustering of Galaxies: A Study using SDSS-III
We investigate the effects of potential sources of systematic error on the
angular and photometric redshift, z_phot, distributions of a sample of redshift
0.4 < z < 0.7 massive galaxies whose selection matches that of the Baryon
Oscillation Spectroscopic Survey (BOSS) constant mass sample. Utilizing over
112,778 BOSS spectra as a training sample, we produce a photometric redshift
catalog for the galaxies in the SDSS DR8 imaging area that, after masking,
covers nearly one quarter of the sky (9,913 square degrees). We investigate
fluctuations in the number density of objects in this sample as a function of
Galactic extinction, seeing, stellar density, sky background, airmass,
photometric offset, and North/South Galactic hemisphere. We find that the
presence of stars of comparable magnitudes to our galaxies (which are not
traditionally masked) effectively remove area. Failing to correct for such
stars can produce systematic errors on the measured angular auto-correlation
function, w, that are larger than its statistical uncertainty. We describe how
one can effectively mask for the presence of the stars, without removing any
galaxies from the sample, and minimize the systematic error. Additionally, we
apply two separate methods that can be used to correct the systematic errors
imparted by any parameter that can be turned into a map on the sky. We find
that failing to properly account for varying sky background introduces a
systematic error on w. We measure w, in four z_phot slices of width 0.05
between 0.45 < z_phot < 0.65 and find that the measurements, after correcting
for the systematic effects of stars and sky background, are generally
consistent with a generic LambdaCDM model, at scales up to 60 degrees. At
scales greater than 3 degrees and z_phot > 0.5, the magnitude of the
corrections we apply are greater than the statistical uncertainty in w.Comment: Accepted by MNRA
Photometric redshifts and quasar probabilities from a single, data-driven generative model
We describe a technique for simultaneously classifying and estimating the
redshift of quasars. It can separate quasars from stars in arbitrary redshift
ranges, estimate full posterior distribution functions for the redshift, and
naturally incorporate flux uncertainties, missing data, and multi-wavelength
photometry. We build models of quasars in flux-redshift space by applying the
extreme deconvolution technique to estimate the underlying density. By
integrating this density over redshift one can obtain quasar flux-densities in
different redshift ranges. This approach allows for efficient, consistent, and
fast classification and photometric redshift estimation. This is achieved by
combining the speed obtained by choosing simple analytical forms as the basis
of our density model with the flexibility of non-parametric models through the
use of many simple components with many parameters. We show that this technique
is competitive with the best photometric quasar classification
techniques---which are limited to fixed, broad redshift ranges and high
signal-to-noise ratio data---and with the best photometric redshift techniques
when applied to broadband optical data. We demonstrate that the inclusion of UV
and NIR data significantly improves photometric quasar--star separation and
essentially resolves all of the redshift degeneracies for quasars inherent to
the ugriz filter system, even when included data have a low signal-to-noise
ratio. For quasars spectroscopically confirmed by the SDSS 84 and 97 percent of
the objects with GALEX UV and UKIDSS NIR data have photometric redshifts within
0.1 and 0.3, respectively, of the spectroscopic redshift; this amounts to about
a factor of three improvement over ugriz-only photometric redshifts. Our code
to calculate quasar probabilities and redshift probability distributions is
publicly available
The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
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.Comment: 9 figures; 2 tables. Submitted to ApJS. DR9 is available at
http://www.sdss3.org/dr
The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
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.Comment: Astrophysical Journal Supplements, in press (minor updates from
submitted version
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in
operation since July 2014. This paper describes the second data release from
this phase, and the fourteenth from SDSS overall (making this, Data Release
Fourteen or DR14). This release makes public data taken by SDSS-IV in its first
two years of operation (July 2014-2016). Like all previous SDSS releases, DR14
is cumulative, including the most recent reductions and calibrations of all
data taken by SDSS since the first phase began operations in 2000. New in DR14
is the first public release of data from the extended Baryon Oscillation
Spectroscopic Survey (eBOSS); the first data from the second phase of the
Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2),
including stellar parameter estimates from an innovative data driven machine
learning algorithm known as "The Cannon"; and almost twice as many data cubes
from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous
release (N = 2812 in total). This paper describes the location and format of
the publicly available data from SDSS-IV surveys. We provide references to the
important technical papers describing how these data have been taken (both
targeting and observation details) and processed for scientific use. The SDSS
website (www.sdss.org) has been updated for this release, and provides links to
data downloads, as well as tutorials and examples of data use. SDSS-IV is
planning to continue to collect astronomical data until 2020, and will be
followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14
happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov
2017 (this is the "post-print" and "post-proofs" version; minor corrections
only from v1, and most of errors found in proofs corrected
The Sloan Digital Sky Survey quasar catalog: tenth data release
We present the Data Release 10 Quasar (DR10Q) catalog from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. The catalog includes all BOSS objects that were targeted as quasar candidates during the first 2.5 years of the survey and that are confirmed as quasars via visual inspection of the spectra, have luminosities M-i[z = 2] 2.15 (117 668) is similar to 5 times greater than the number of z > 2.15 quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (C IV, C III, Mg II). The catalog identifies 16 461 broad absorption line quasars and gives their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag and information on the optical morphology and selection method. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3600-10 500 angstrom at a spectral resolution in the range 1300 < R < 2500; the spectra can be retrieved from the SDSS Catalog Archive Server. We also provide a supplemental list of an additional 2376 quasars that have been identified among the galaxy targets of the SDSS-III/BOSS
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