94 research outputs found
A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies
We have conducted a systematic search of low-mass black holes (BHs) in active
galactic nuclei (AGNs) with broad Halpha emission lines, aiming at building a
homogeneous sample that is more complete than previous ones for fainter, less
highly accreting sources. For this purpose, we developed a set of elaborate,
automated selection procedures and applied it uniformly to the Fourth Data
Release of the Sloan Digital Sky Survey. Special attention is given to
AGN--galaxy spectral decomposition and emission-line deblending. We define a
sample of 309 type 1 AGNs with BH masses in the range -- \msun (with a median of solar mass), using the
virial mass estimator based on the broad Halpha line. About half of our sample
of low-mass BHs differs from that of Greene & Ho, with 61 of them discovered
here for the first time. Our new sample picks up more AGNs with low accretion
rates: the Eddington ratios of the present sample range from to ~1,
with 30% below 0.1. This suggests that a significant fraction of low-mass BHs
in the local Universe are accreting at low rates. The host galaxies of the
low-mass BHs have luminosities similar to those of field galaxies,
optical colors of Sbc spirals, and stellar spectral features consistent with a
continuous star formation history with a mean stellar age of less than 1 Gyr.Comment: Accepted for publication in Ap
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Analysis of potential systematics
We analyze the density field of galaxies observed by the Sloan Digital Sky
Survey (SDSS)-III Baryon Oscillation Spectroscopic Survey (BOSS) included in
the SDSS Data Release Nine (DR9). DR9 includes spectroscopic redshifts for over
400,000 galaxies spread over a footprint of 3,275 deg^2. We identify,
characterize, and mitigate the impact of sources of systematic uncertainty on
large-scale clustering measurements, both for angular moments of the
redshift-space correlation function and the spherically averaged power
spectrum, P(k), in order to ensure that robust cosmological constraints will be
obtained from these data. A correlation between the projected density of stars
and the higher redshift (0.43 < z < 0.7) galaxy sample (the `CMASS' sample) due
to imaging systematics imparts a systematic error that is larger than the
statistical error of the clustering measurements at scales s > 120h^-1Mpc or k
< 0.01hMpc^-1. We find that these errors can be ameliorated by weighting
galaxies based on their surface brightness and the local stellar density. We
use mock galaxy catalogs that simulate the CMASS selection function to
determine that randomly selecting galaxy redshifts in order to simulate the
radial selection function of a random sample imparts the least systematic error
on correlation function measurements and that this systematic error is
negligible for the spherically averaged correlation function. The methods we
recommend for the calculation of clustering measurements using the CMASS sample
are adopted in companion papers that locate the position of the baryon acoustic
oscillation feature (Anderson et al. 2012), constrain cosmological models using
the full shape of the correlation function (Sanchez et al. 2012), and measure
the rate of structure growth (Reid et al. 2012). (abridged)Comment: Matches version accepted by MNRAS. Clarifications and references have
been added. See companion papers that share the "The clustering of galaxies
in the SDSS-III Baryon Oscillation Spectroscopic Survey:" titl
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey : baryon acoustic oscillations in the Data Releases 10 and 11 Galaxy samples
We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations (BAO) in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey, which is part of the Sloan Digital Sky Survey III. Our results come from the Data Release 11 (DR11) sample, containing nearly one million galaxies and covering approximately 8500 square degrees and the redshift range 0.2 < z < 0.7. We also compare these results with those from the publicly released DR9 and DR10 samples. Assuming a concordance Î cold dark matter (ÎCDM) cosmological model, the DR11 sample covers a volume of 13 Gpc3 and is the largest region of the Universe ever surveyed at this density. We measure the correlation function and power spectrum, including density-field reconstruction of the BAO feature. The acoustic features are detected at a significance of over 7Ï in both the correlation function and power spectrum. Fitting for the position of the acoustic features measures the distance relative to the sound horizon at the drag epoch, rd, which has a value of rd,fid = 149.28âMpc in our fiducial cosmology. We find DV = (1264 ± 25âMpc)(rd/rd,fid) at z = 0.32 and DV = (2056 ± 20âMpc)(rd/rd,fid) at z = 0.57. At 1.0 per cent, this latter measure is the most precise distance constraint ever obtained from a galaxy survey. Separating the clustering along and transverse to the line of sight yields measurements at z = 0.57 of DA = (1421 ± 20âMpc)(rd/rd,fid) and H = (96.8 ± 3.4âkmâsâ1âMpcâ1)(rd,fid/rd). Our measurements of the distance scale are in good agreement with previous BAO measurements and with the predictions from cosmic microwave background data for a spatially flat CDM model with a cosmological constant.Publisher PDFPeer reviewe
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The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the Data Release 9 Spectroscopic Galaxy Sample
We present measurements of galaxy clustering from the Baryon Oscillation
Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey III
(SDSS-III). These use the Data Release 9 (DR9) CMASS sample, which contains
264,283 massive galaxies covering 3275 square degrees with an effective
redshift z=0.57 and redshift range 0.43 < z < 0.7. Assuming a concordance
Lambda-CDM cosmological model, this sample covers an effective volume of 2.2
Gpc^3, and represents the largest sample of the Universe ever surveyed at this
density, n = 3 x 10^-4 h^-3 Mpc^3. We measure the angle-averaged galaxy
correlation function and power spectrum, including density-field reconstruction
of the baryon acoustic oscillation (BAO) feature. The acoustic features are
detected at a significance of 5\sigma in both the correlation function and
power spectrum. Combining with the SDSS-II Luminous Red Galaxy Sample, the
detection significance increases to 6.7\sigma. Fitting for the position of the
acoustic features measures the distance to z=0.57 relative to the sound horizon
DV /rs = 13.67 +/- 0.22 at z=0.57. Assuming a fiducial sound horizon of 153.19
Mpc, which matches cosmic microwave background constraints, this corresponds to
a distance DV(z=0.57) = 2094 +/- 34 Mpc. At 1.7 per cent, this is the most
precise distance constraint ever obtained from a galaxy survey. We place this
result alongside previous BAO measurements in a cosmological distance ladder
and find excellent agreement with the current supernova measurements. We use
these distance measurements to constrain various cosmological models, finding
continuing support for a flat Universe with a cosmological constant.Comment: 33 page
A single-electron transistor made from a cadmium selenide nanocrystal
The techniques of colloidal chemistry permit the routine creation of
semiconductor nanocrystals, whose dimensions are much smaller than those that
can be realized using lithographic techniques. The sizes of such nanocrystals
can be varied systematically to study quantum size effects or to make novel
electronic or optical materials with tailored properties. Preliminary studies
of both the electrical and optical properties of individual nanocrystals have
been performed recently. These studies show clearly that a single excess charge
on a nanocrystal can markedly influence its properties. Here we present
measurements of electrical transport in a single-electron transistor made from
a colloidal nanocrystal of cadmium selenide. This device structure enables the
number of charge carriers on the nanocrystal to be tuned directly, and so
permits the measurement of the energy required for adding successive charge
carriers. Such measurements are invaluable in understanding the energy-level
spectra of small electronic systems, as has been shown by similar studies of
lithographically patterned quantum dots and small metallic grains.Comment: 3 pages, PDF forma
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 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 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 : fourteenth data release
We present the data release 14 Quasar catalog (DR14Q) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV). This catalog includes all SDSS-IV/eBOSS objects that were spectroscopically targeted as quasar candidates and that are confirmed as quasars via a new automated procedure combined with a partial visual inspection of spectra, have luminosities Mi [z = 2] < â20.5 (in a Î CDM cosmology with H0 = 70 km sâ1 Mpcâ1, ΩM =0.3, and ΩΠ= 0.7), and either display at least one emission line with a full width at half maximum larger than 500 km sâ1 or, if not, have interesting/complex absorption features. The catalog also includes previously spectroscopically-confirmed quasars from SDSS-I, II, and III. The catalog contains 526 356 quasars (144 046 are new discoveries since the beginning of SDSS-IV) detected over 9376 deg2 (2044 deg2 having new spectroscopic data available) with robust identification and redshift measured by a combination of principal component eigenspectra. The catalog is estimated to have about 0.5% contamination. Redshifts are provided for the Mg II emission line. The catalog identifies 21 877 broad absorption line quasars and lists 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. 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, covering the wavelength region 3610â10 140 â« at a spectral resolution in the range 1300 < R < 2500, can be retrieved from the SDSS Science Archiver Server.Publisher PDFPeer reviewe
The Rest-Frame Optical Luminosity Function of Cluster Galaxies at z<0.8 and the Assembly of the Cluster Red Sequence
We present the rest-frame optical luminosity function (LF) of red sequence
galaxies in 16 clusters at 0.4<z<0.8 drawn from the ESO Distant Cluster Survey
(EDisCS). We compare our clusters to an analogous sample from the Sloan Digital
Sky Survey (SDSS) and match the EDisCS clusters to their most likely
descendants. We measure all LFs down to M M* + (2.5 - 3.5). At z<0.8, the
bright end of the LF is consistent with passive evolution but there is a
significant build-up of the faint end of the red sequence towards lower
redshift. There is a weak dependence of the LF on cluster velocity dispersion
for EDisCS but no such dependence for the SDSS clusters. We find tentative
evidence that red sequence galaxies brighter than a threshold magnitude are
already in place, and that this threshold evolves to fainter magnitudes toward
lower redshifts. We compare the EDisCS LFs with the LF of co-eval red sequence
galaxies in the field and find that the bright end of the LFs agree. However,
relative to the number of bright red galaxies, the field has more faint red
galaxies than clusters at 0.6<z<0.8 but fewer at 0.4<z<0.6, implying
differential evolution. We compare the total light in the EDisCS cluster red
sequences to the total red sequence light in our SDSS cluster sample. Clusters
at 0.4<z<0.8 must increase their luminosity on the red sequence (and therefore
stellar mass in red galaxies) by a factor of 1-3 by z=0. The necessary
processes that add mass to the red sequence in clusters predict local clusters
that are over-luminous as compared to those observed in the SDSS. The predicted
cluster luminosities can be reconciled with observed local cluster luminosities
by combining multiple previously known effects.Comment: Accepted for publication in the Astrophysical Journal. 36 pages, 16
figures, 10 table
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