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391. Karhunen-Loeve transform of SDSS QSOs
ID:
ivo://CDS.VizieR/J/AJ/140/390
Title:
Karhunen-Loeve transform of SDSS QSOs
Short Name:
J/AJ/140/390
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Karhunen-Loeve (KL) transform can compactly represent the information contained in large, complex datasets, cleanly eliminating noise from the data and identifying elements of the dataset with extreme or inconsistent characteristics. We develop techniques to apply the KL transform to the 4000-5700{AA} region of 9800 QSO spectra with z<0.619 from the SDSS archive. Up to 200 eigenspectra are needed to fully reconstruct the spectra in this sample to the limit of their signal-to-noise (S/N). We propose a simple formula for selecting the optimum number of eigenspectra to use to reconstruct any given spectrum, based on the S/N of the spectrum, but validated by formal cross-validation tests.
392. K-band light curve of GRS 1915+105
ID:
ivo://CDS.VizieR/J/ApJ/657/409
Title:
K-band light curve of GRS 1915+105
Short Name:
J/ApJ/657/409
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of 7 years of K-band monitoring of the low-mass X-ray binary GRS 1915+105. Positive correlations between the infrared flux and the X-ray flux and X-ray hardness are demonstrated. Analysis of the frequency spectrum shows that the orbital period of the system is P_orb_=30.8+/-0.2days. The phase and amplitude of the orbital modulation suggests that the modulation is due to the heating of the face of the secondary star. We also report another periodic signature between 31.2 and 31.6days, most likely due to a superhump resonance. From the superhump period we then obtain a range for the mass ratio of the system, 0.05<q<0.12.
393. Keck ESI observations of Ly{alpha} systems
ID:
ivo://CDS.VizieR/J/ApJ/721/1
Title:
Keck ESI observations of Ly{alpha} systems
Short Name:
J/ApJ/721/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first results from a survey of SDSS quasars selected for strong HI damped Ly{alpha} (DLA) absorption with corresponding low equivalent width absorption from strong low-ion transitions (e.g., CII{lambda}1334 and SiII{lambda}1260). These metal-poor DLA candidates were selected from the SDSS fifth release quasar spectroscopic database, and comprise a large new sample for probing low-metallicity galaxies. Medium-resolution echellette spectra from the Keck Echellette Spectrograph and Imager spectrograph for an initial sample of 35 systems were obtained to explore the metal-poor tail of the DLA distribution and to investigate the nucleosynthetic patterns at these metallicities. We have estimated saturation corrections for the moderately underresolved spectra, and systems with very narrow Doppler parameters (b<=5km/s) will likely have underestimated abundances. For those systems with Doppler parameters b>5km/s, we have measured low-metallicity DLA gas with [X/H]<-2.4 for at least one of C, O, Si, or Fe. Assuming non-saturated components, we estimate that several DLA systems have [X/H]<-2.8, including five DLA systems with both low equivalent widths and low metallicity in transitions of both CII and OI. All of the measured DLA metallicities, however, exceed or are consistent with a metallicity of at least 1/1000 of solar, regardless of the effects of saturation in our spectra.
394. Keck+Magellan survey for LLSs. III.
ID:
ivo://CDS.VizieR/J/ApJS/221/2
Title:
Keck+Magellan survey for LLSs. III.
Short Name:
J/ApJS/221/2
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an absorption-line survey of optically thick gas clouds --Lyman Limit Systems (LLSs)-- observed at high dispersion with spectrometers on the Keck and Magellan telescopes. We measure column densities of neutral hydrogen N_H1_ and associated metal-line transitions for 157 LLSs at z_LLS_=1.76-4.39 restricted to 10^17.3^cm^-2^<=N_HI_<10^20.3^cm^-2^. An empirical analysis of ionic ratios indicates an increasing ionization state of the gas with decreasing N_H1_ and that the majority of LLSs are highly ionized, confirming previous expectations. The Si^+^/H^0^ ratio spans nearly four orders of magnitude, implying a large dispersion in the gas metallicity. Fewer than 5% of these LLSs have no positive detection of a metal transition; by z~3 nearly all gas that is dense enough to exhibit a very high Lyman limit opacity has previously been polluted by heavy elements. We add new measurements to the small subset of LLS (~5%-10%) that may have super-solar abundances. High Si^+^/Fe^+^ ratios suggest an {alpha}-enhanced medium, whereas the Si^+^/C^+^ ratios do not exhibit the super-solar enhancement inferred previously for the Ly{alpha} forest.
395. KiDS-BEXGO catalog
ID:
ivo://CDS.VizieR/J/A+A/632/A56
Title:
KiDS-BEXGO catalog
Short Name:
J/A+A/632/A56
Date:
21 Oct 2021
Publisher:
CDS
Description:
Within a Kilo-Degree Survey (KiDS) Strongly lensed QUAsar Detection project (KiDS-SQuaD), we built a catalogue of bright extragalactic objects from the KiDS DR4, with the main objective to select the reliable gravitationally lensed quasar candidates. We used machine learning algorithm, trained on Sloan Digital Sky Survey DR14 data, to classify sources from subsample (r<22mag) of KiDS DR4 on three classes: stars, quasars and galaxies. Resulting KiDS Bright EXtraGalactic Objects catalogue (KiDS-BEXGO) contains ~6M galaxies and ~0.2M quasars. KiDS-BEXGO represents the first comprehensive identification of bright extragalactic objects in the KiDS DR4 data.
396. KiDS DR3 QSO catalog
ID:
ivo://CDS.VizieR/J/A+A/624/A13
Title:
KiDS DR3 QSO catalog
Short Name:
J/A+A/624/A13
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of quasars selected from broad-band photometric ugri data of the Kilo-Degree Survey Data Release 3 (KiDS DR3). The QSOs are identified by the random forest (RF) supervised machine learning model, trained on Sloan Digital Sky Survey (SDSS) DR14 spectroscopic data. We first cleaned the input KiDS data of entries with excessively noisy, missing or otherwise problematic measurements. Applying a feature importance analysis, we then tune the algorithm and identify in the KiDS multiband catalog the 17 most useful features for the classification, namely magnitudes, colors, magnitude ratios, and the stellarity index. We used the t-SNE algorithm to map the multidimensional photometric data onto 2D planes and compare the coverage of the training and inference sets. We limited the inference set to r<22 to avoid extrapolation beyond the feature space covered by training, as the SDSS spectroscopic sample is considerably shallower than KiDS. This gives 3.4 million objects in the final inference sample, from which the random forest identified 190,000 quasar candidates. Accuracy of 97% (percentage of correctly classified objects), purity of 91% (percentage of true quasars within the objects classified as such), and completeness of 87% (detection ratio of all true quasars), as derived from a test set extracted from SDSS and not used in the training, are confirmed by comparison with external spectroscopic and photometric QSO catalogs overlapping with the KiDS footprint. The robustness of our results is strengthened by number counts of the quasar candidates in the r band, as well as by their mid-infrared colors available from the Wide-field Infrared Survey Explorer (WISE). An analysis of parallaxes and proper motions of our QSO candidates found also in Gaia DR2 suggests that a probability cut of pQSO>0.8 is optimal for purity, whereas pQSO>0.7 is preferable for better completeness. Our study presents the first comprehensive quasar selection from deep high-quality KiDS data and will serve as the basis for versatile studies of the QSO population detected by this survey. We publicly release the resulting catalog at http://kids.strw.leidenuniv.nl/DR3/quasarcatalog.php, and the code at https://github.com/snakoneczny/kids-quasars
397. Kinematics of parsec-scale radio jets
ID:
ivo://CDS.VizieR/J/ApJ/609/539
Title:
Kinematics of parsec-scale radio jets
Short Name:
J/ApJ/609/539
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the results of a 15GHz (2cm) multi-epoch Very Long Baseline Array (VLBA) program, begun in 1994 to study the outflow in radio jets ejected from quasars and active galaxies.
398. Kitt Peak Quasar List
ID:
ivo://CDS.VizieR/VII/11
Title:
Kitt Peak Quasar List
Short Name:
VII/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalog includes the complete source list with positions of the Kitt Peak Quasar Catalog (de Veny et al., 1971PASP...83..611D). Other fields in the de Veny catalog (4C ID, B1950 equatorial positions, V, B-V, U-B, z, references to ID UBV z, and Notes and other references) are not included. The Kitt Peak Quasar Catalog sources were selected based on optical data for all confirmed quasars published prior to May or June 1971. This includes objects with only one spectral line. The published catalog includes a bibliography for all quasars with redshifts The source list also includes some additional sources included by the author.
399. Known quasars in the QUEST Variability Survey
ID:
ivo://CDS.VizieR/J/AJ/131/1923
Title:
Known quasars in the QUEST Variability Survey
Short Name:
J/AJ/131/1923
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present variability and multiwavelength photometric information for the 933 known quasars in the QUEST Variability Survey (Cat. <II/266>). These quasars are grouped into variable and nonvariable populations based on measured variability confidence levels.
400. KODIAQ DR2
ID:
ivo://CDS.VizieR/J/AJ/154/114
Title:
KODIAQ DR2
Short Name:
J/AJ/154/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present and make publicly available the second data release (DR2) of the Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) survey. KODIAQ DR2 consists of a fully reduced sample of 300 quasars at 0.07<z_em_<5.29 observed with HIRES at high resolution (36000{<=}R{<=}103000). DR2 contains 831 spectra available in continuum normalized form, representing a sum total exposure time of ~4.9 megaseconds on source. These co-added spectra arise from a total of 1577 individual exposures of quasars taken from the Keck Observatory Archive (KOA) in raw form and uniformly processed. DR2 extends DR1 by adding 130 new quasars to the sample, including additional observations of QSOs in DR1. All new data in DR2 were obtained with the single-chip Tektronix TK2048 CCD configuration of HIRES in operation between 1995 and 2004. DR2 is publicly available to the community, housed as a higher level science product at the KOA and in the igmspec database (v03).