- ID:
- ivo://CDS.VizieR/J/MNRAS/465/1831
- Title:
- SDSS-IV eBOSS ELG UgrizW photometry
- Short Name:
- J/MNRAS/465/1831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present two wide-field catalogues of photometrically selected emission line galaxies (ELGs) at z~=0.8 covering about 2800deg^2^ over the south galactic cap. The catalogues were obtained using a Fisher discriminant technique described in a companion paper. The two catalogues differ by the imaging used to define the Fisher discriminant: the first catalogue includes imaging from the Sloan Digital Sky Survey and the Wide-field InfraredSurvey Explorer, the second also includes information from the South Galactic Cap U-band Sky Survey. Containing respectively 560045 and 615601 objects, they represent the largest ELG catalogues available today and were designed for the ELG programme of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). We study potential sources of systematic variation in the angular distribution of the selected ELGs due to fluctuations of the observational parameters. We model the influence of the observational parameters using a multivariate regression and implement a weighting scheme which allows effective removal of all of the systematic errors induced by the observational parameters. We show that fluctuations in the imaging zero-points of the photometric bands have minor impact on the angular distribution of objects in our catalogues. We compute the angular clustering of both catalogues and show that our weighting procedure effectively removes spurious clustering on large scales. We fit a model to the small-scale angular clustering, showing that the selections have similar biases of 1.35/Da(z) and 1.28/Da(z). Both catalogues are publicly available.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/592/A121
- Title:
- SDSS-IV eBOSS emission-line galaxy pilot survey
- Short Name:
- J/A+A/592/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Digital Sky Survey IV extended Baryonic Oscillation Spectroscopic Survey (SDSS-IV/eBOSS) will observe 195,000 emission-line galaxies (ELGs) to measure the Baryonic Acoustic Oscillation standard ruler (BAO) at redshift 0.9. To test different ELG selection algorithms, based on data from several imaging surveys, 9,000 spectra were observed with the SDSS spectrograph as a pilot survey. First, using visual inspection and redshift quality flags, we find that the automated spectroscopic redshifts assigned by the pipeline meet the quality requirements for a robust BAO measurement. Also, we show the correlations between sky emission, signal-to-noise ratio in the emission lines and redshift error. Then we provide a detailed description of each target selection algorithm tested and compare them with the requirements of the eBOSS experiment. As a result, we provide robust redshift distributions for the different target selection schemes tested. Finally, we infer two optimal target selection algorithms to be applied on DECam photometry that fulfill the eBOSS survey electronic efficiency requirements.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A97
- Title:
- SDSS-IV/SPIDERS X-ray PS Spectroscopic Catalog
- Short Name:
- J/A+A/636/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We look to provide a detailed description of the SPectroscopic IDentification of ERosita Sources (SPIDERS) survey, an SDSS-IV programme aimed at obtaining spectroscopic classification and redshift measurements for complete samples of sufficiently bright X-ray sources. We describe the SPIDERS X-ray Point Source Spectroscopic Catalogue, considering its store of 11092 observed spectra drawn from a parent sample of 14759 ROSAT and XMM sources over an area of 5129deg^2^ covered in SDSS-IV by the eBOSS survey. This programme represents the largest systematic spectroscopic observation of an X-ray selected sample. A total of 10970 (98.9%) of the observed objects are classified and 10849 (97.8%) have secure redshifts. The majority of the spectra (10070 objects) are active galactic nuclei (AGN), 522 are cluster galaxies, and 294 are stars. The observed AGN redshift distribution is in good agreement with simulations based on empirical models for AGN activation and duty cycle. Forming composite spectra of type 1 AGN as a function of the mass and accretion rate of their black holes reveals systematic differences in the H-beta emission line profiles. This study paves the way for systematic spectroscopic observations of sources that are potentially to be discovered in the upcoming eROSITA survey over a large section of the sky.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/3430
- Title:
- SDSS-2MASS-WISE stellar colour locus
- Short Name:
- J/MNRAS/440/3430
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the fiducial main-sequence stellar locus traced by 10 photometric colours observed by Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey (2MASS), and Wide-field Infrared Survey Explorer} (WISE). Median colours are determined using 1052 793 stars with r-band extinction less than 0.125. We use this locus to measure the dust extinction curve relative to the r band, which is consistent with previous measurements in the SDSS and 2MASS bands. The WISE band extinction coefficients are larger than predicted by standard extinction models. Using 13 lines of sight, we find variations in the extinction curve in H, Ks, and WISE bandpasses. Relative extinction decreases towards Galactic anticentre, in agreement with prior studies. Relative extinction increases with Galactic latitude, in contrast to previous observations. This indicates a universal mid-IR extinction law does not exist due to variations in dust grain size and chemistry with Galactocentric position. A preliminary search for outliers due to warm circumstellar dust is also presented, using stars with high signal-to-noise ratio in the W3 band. We find 199 such outliers, identified by excess emission in Ks-W3. Inspection of SDSS images for these outliers reveals a large number of contaminants due to nearby galaxies. Six sources appear to be genuine dust candidates, yielding a fraction of systems with infrared excess of 0.12+/-0.05 per cent.
- ID:
- ivo://CDS.VizieR/J/MNRAS/387/1323
- Title:
- SDSS photometry of luminous red galaxies
- Short Name:
- J/MNRAS/387/1323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the AAT-AAOmega LRG Pilot observing run to establish the feasibility of a large spectroscopic survey using the new AAOmega instrument. We have selected luminous red galaxies (LRGs) using single epoch SDSS riz-photometry to i<20.5 and z<20.2. We have observed in three fields including the COSMOS field and the COMBO-17 S11 field, obtaining a sample of ~600 redshift z>~0.5 LRGs. Exposure times varied from 14h to determine the minimum exposure for AAOmega to make an essentially complete LRG redshift survey in average conditions. We show that LRG redshifts to i<20.5 can be measured in >>1.5h exposures and present comparisons with 2SLAQ and COMBO-17 (photo)redshifts. Crucially, the riz selection coupled with the three to four times improved AAOmega throughput is shown to extend the LRG mean redshift from z=0.55 for 2SLAQ to z=0.681+/-0.005 for riz-selected LRGs. This extended range is vital for maximizing the signal-to-noise ratio for the detection of the baryon acoustic oscillations (BAOs). Furthermore, we show that the amplitude of LRG clustering is s_0_=9.9+/-0.7h^-1^Mpc, as high as that seen in the 2SLAQ LRG Survey. Consistent results for this clustering amplitude are found from the projected and semi-projected correlation functions. This high amplitude is consistent with a long-lived population whose bias evolves as predicted by a simple 'high-peak' model. We conclude that a redshift survey of 360000 LRGs over 3000deg^2^, with an effective volume some four times bigger than previously used to detect BAO with LRGs, is possible with AAOmega in 170 nights.
1486. SDSS QSO DR7 and DR9
- ID:
- ivo://CDS.VizieR/J/A+A/616/A97
- Title:
- SDSS QSO DR7 and DR9
- Short Name:
- J/A+A/616/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The explosion of data in recent years has generated an increasing need for new analysis techniques in order to extract knowledge from massive data-sets. Machine learning has proved particularly useful to perform this task. Fully automatized methods (e.g. deep neural networks) have recently gathered great popularity, even though those methods often lack physical interpretability. In contrast, feature based approaches can provide both well-performing models and understandable causalities with respect to the correlations found between features and physical processes. Efficient feature selection is an essential tool to boost the performance of machine learning models. In this work, we propose a forward selection method in order to compute, evaluate, and characterize better performing features for regression and classification problems. Given the importance of photometric redshift estimation, we adopt it as our case study. We synthetically created 4520 features by combining magnitudes, errors, radii, and ellipticities of quasars, taken from the Sloan Digital Sky Survey (SDSS). We apply a forward selection process, a recursive method in which a huge number of feature sets is tested through a k-Nearest-Neighbours algorithm, leading to a tree of feature sets. The branches of the feature tree are then used to perform experiments with the random forest, in order to validate the best set with an alternative model. We demonstrate that the sets of features determined with our approach improve the performances of the regression models significantly when compared to the performance of the classic features from the literature. The found features are unexpected and surprising, being very different from the classic features. Therefore, a method to interpret some of the found features in a physical context is presented. The feature selection methodology described here is very general and can be used to improve the performance of machine learning models for any regression or classification task.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/17
- Title:
- SDSS QSO DR14 spectral properties
- Short Name:
- J/ApJS/249/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the spectral properties for a total of 526,265 quasars, out of which 63% have a continuum signal-to-noise ratio >3pixel^-1^, selected from the fourteenth data release of the Sloan Digital Sky Survey (SDSS-DR14) quasar catalog. We performed a careful and homogeneous analysis of the SDSS spectra of these sources to estimate the continuum and line properties of several emission lines such as H{alpha}, H{beta}, H{gamma}, MgII, CIII], CIV, and Ly{alpha}. From the derived emission line parameters, we estimated single-epoch virial black hole masses (M_BH_) for the sample using H{beta}, MgII, and CIV emission lines. The sample covers a wide range in bolometric luminosity (logLbol; erg/s) between 44.4 and 47.3 and logM_BH_ between 7.1 and 9.9M_{sin}_. Using the ratio of Lbol to the Eddington luminosity as a measure of the accretion rate, the logarithm of the accretion rate is found to be in the range between -2.06 and 0.43. We performed several correlation analyses between different emission line parameters and found them to match the correlation known earlier using smaller samples. We note that strong FeII sources with a large Balmer line width and highly accreting sources with large M BH are rare in our sample. We make an extended and complete catalog available online that contains various spectral properties of 526,265 quasars derived in this work along with other properties culled from the SDSS-DR14 quasar catalog.
- ID:
- ivo://CDS.VizieR/VII/269
- Title:
- SDSS Quasar Catalog, DR9Q
- Short Name:
- VII/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Data Release 9 Quasar (DR9Q) 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 survey, are spectroscopically confirmed as quasars via visual inspection. This catalog contains 87,822 quasars (78,086 are new discoveries) detected over 3,275{deg}^2^ with robust identification and redshift measured by a combination of principal component eigenspectra newly derived from a training set of 8,632 spectra from SDSS-DR7. The number of quasars with z>2.15 (61,931) is 2.8 times larger than the number of z>2.15 quasars previously known. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII], MgII). The catalog identifies 7,533 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 0.03mag, and information on the 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. We also provide a supplemental list of an additional 949 quasars that have been identified, among galaxy targets of the BOSS or among quasar targets after DR9 was frozen.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A66
- Title:
- SDSS Quasar Catalog, DR9Q
- Short Name:
- VII/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Data Release 9 Quasar (DR9Q) 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 survey, are spectroscopically confirmed as quasars via visual inspection. This catalog contains 87,822 quasars (78,086 are new discoveries) detected over 3,275°<SUP>2</SUP> with robust identification and redshift measured by a combination of principal component eigenspectra newly derived from a training set of 8,632 spectra from SDSS-DR7. The number of quasars with z>2.15 (61,931) is 2.8 times larger than the number of z>2.15 quasars previously known. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII], MgII). The catalog identifies 7,533 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 0.03mag, and information on the 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. We also provide a supplemental list of an additional 949 quasars that have been identified, among galaxy targets of the BOSS or among quasar targets after DR9 was frozen.
- ID:
- ivo://CDS.VizieR/VII/286
- Title:
- SDSS quasar catalog, fourteenth data release
- Short Name:
- VII/286
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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] < -20.5 (in a {LAMBDA} CDM cosmology with H_0_=70km/s/Mpc, {OMEGA}_M_=0.3, and {OMEGA}_{LAMBDA}_=0.7), and either display at least one emission line with a full width at half maximum larger than 500km/s 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 526356 quasars (144046 are new discoveries since the beginning of SDSS-IV) detected over 9376 deg^2^ (2044 deg^2^ 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 MgII emission line. The catalog identifies 21877 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 0.03mag. 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 3610-10140{AA} at a spectral resolution in the range 1300<R<2500, can be retrieved from the SDSS Science Archiver Server.
