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471. Maidanak Observatory Lens Images
ID:
ivo://org.gavo.dc/maidanak/res/rawframes/rawframes
Title:
Maidanak Observatory Lens Images
Date:
22 Jan 2021 08:24:03
Publisher:
The GAVO DC team
Description:
Observations of (mainly) lensed quasars from Maidanak Observatory, Uzbekhistan
472. Maidanak Observatory Lens Images
ID:
ivo://org.gavo.dc/maidanak/res/rawframes/reduced
Title:
Maidanak Observatory Lens Images
Short Name:
maidanak.reduced
Date:
27 Dec 2024 08:31:04
Publisher:
The GAVO DC team
Description:
Reduced frames of lensed quasar observations from Maidanak Observatory. See the referenceURL for details on the reduction procedure and calibration data.
473. MASIV Survey. IV. Radio AGNs variability
ID:
ivo://CDS.VizieR/J/MNRAS/474/4396
Title:
MASIV Survey. IV. Radio AGNs variability
Short Name:
J/MNRAS/474/4396
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the relationship between 5GHz interstellar scintillation (ISS) and 15GHz intrinsic variability of compact, radio-selected active galactic nuclei (AGNs) drawn from the Microarcsecond Scintillation-Induced Variability (MASIV) Survey and the Owens Valley Radio Observatory blazar monitoring program. We discover that the strongest scintillators at 5GHz (modulation index, m_5_>=0.02) all exhibit strong 15GHz intrinsic variability (m_15_>=0.1). This relationship can be attributed mainly to the mutual dependence of intrinsic variability and ISS amplitudes on radio core compactness at ~100{mu}s scales, and to a lesser extent, on their mutual dependences on source flux density, arcsec-scale core dominance and redshift. However, not all sources displaying strong intrinsic variations show high amplitude scintillation, since ISS is also strongly dependent on Galactic line-of-sight scattering properties. This observed relationship between intrinsic variability and ISS highlights the importance of optimizing the observing frequency, cadence, timespan and sky coverage of future radio variability surveys, such that these two effects can be better distinguished to study the underlying physics. For the full MASIV sample, we find that Fermi-detected gamma-ray loud sources exhibit significantly higher 5GHz ISS amplitudes than gamma-ray quiet sources. This relationship is weaker than the known correlation between gamma-ray loudness and the 15GHz variability amplitudes, most likely due to jet opacity effects.
474. Mass functions of active black holes
ID:
ivo://CDS.VizieR/J/ApJ/699/800
Title:
Mass functions of active black holes
Short Name:
J/ApJ/699/800
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present mass functions of distant actively accreting supermassive black holes residing in luminous quasars discovered in the Large Bright Quasar Survey (LBQS), the Bright Quasar Survey (BQS), and the Fall Equatorial Stripe of the Sloan Digital Sky Survey (SDSS). The quasars cover a wide range of redshifts from the local universe to z=5 and were subject to different selection criteria and flux density limits. This makes these samples complementary and can help us gain additional insight on the true underlying black hole mass distribution free from selection effects and mass estimation errors through future studies. We present the relationships used to estimate the black hole mass based on the MgII emission line; the relations are calibrated to the H{beta} and CIV relations by means of several thousand high-quality SDSS spectra. Mass estimates of the individual black holes of these samples are also presented.
475. 2MASS, SDSS and FIRST fluxes of QSOs
ID:
ivo://CDS.VizieR/J/MNRAS/383/1513
Title:
2MASS, SDSS and FIRST fluxes of QSOs
Short Name:
J/MNRAS/383/1513
Date:
21 Oct 2021
Publisher:
CDS
Description:
Starting from a sample of Sloan Digital Sky Survey quasars appearing also in the Two-Micron All-Sky Survey, we study the continuum properties of ~1000 objects observed in eight bands, from near-infrared to ultraviolet. We construct the mean spectral energy distribution (SED) and compare and contrast the continua of radio-loud and radio-quiet quasar (RLQ and RQQ, respectively) objects. The SEDs of the two populations are significantly different, in the sense that RLQs are redder with power-law spectral indices <alpha_RLQ_>=0.55+/-0.04 and <alpha_RQQ_>=0.31+/-0.01 in the spectral range between 10^14.5^ and 10^15.35^Hz. This difference is discussed in terms of different extinctions, different disc temperatures, or slopes of the non-thermal component.
476. 2MASS6x survey of the Lockman Hole
ID:
ivo://CDS.VizieR/J/AJ/125/2521
Title:
2MASS6x survey of the Lockman Hole
Short Name:
J/AJ/125/2521
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have carried out a survey of the Lockman Hole covering over 24deg^2^ using the Two Micron All Sky Survey (2MASS) observing system in a special mode that reaches roughly 1mag deeper than the nominal 2MASS survey. The resultant point-source catalog reaches to approximately (J, H, Ks)<(17.8, 16.5, 16.0)mag with completeness and reliability in excess of 90%-95% at the faintest levels. These data will be useful in identifying sources in SIRTF surveys of this area. We have cataloged 69,115 objects, almost twice as many as in the nominal 2MASS survey of this region. The sample includes a large number of potential new active galaxies, as well as a T dwarf candidate.
477. Metal absorption systems in pairs of QSOs
ID:
ivo://CDS.VizieR/J/MNRAS/392/1539
Title:
Metal absorption systems in pairs of QSOs
Short Name:
J/MNRAS/392/1539
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first large sample of metal absorption systems in pairs of QSOs with sightlines separated by about 1Mpc at z=2. We found 690 absorption systems in the spectra of 310 QSOs in 170 pairings. Most systems show CIV or MgII absorption.
478. Metallicities of damped Ly{alpha} systems
ID:
ivo://CDS.VizieR/J/ApJ/755/89
Title:
Metallicities of damped Ly{alpha} systems
Short Name:
J/ApJ/755/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present chemical abundance measurements for 47 damped Ly{alpha} (DLA) systems, 30 at z>4, observed with the Echellette Spectrograph and Imager and the High Resolution Echelle Spectrometer on the Keck telescopes. H I column densities of the DLAs are measured with Voigt profile fits to the Ly{alpha} profiles, and we find an increased number of false DLA identifications with Sloan Digital Sky Survey at z>4 due to the increased density of the Ly{alpha} forest. Ionic column densities are determined using the apparent optical depth method, and we combine our new metallicity measurements with 195 from previous surveys to determine the evolution of the cosmic metallicity of neutral gas. We find the metallicity of DLAs decreases with increasing redshift, improving the significance of the trend and extending it to higher redshifts, with a linear fit of -0.22+/-0.03 dex per unit redshift from z=0.09-5.06. The metallicity "floor" of {approx}1/600 solar continues out to z~5, despite our sensitivity for finding DLAs with much lower metallicities. However, this floor is not statistically different from a steep tail to the distribution. We also find that the intrinsic scatter of metallicity among DLAs of ~0.5dex continues out to z~5. In addition, the metallicity distribution and the {alpha}/Fe ratios of z>2 DLAs are consistent with being drawn from the same parent population with those of halo stars. It is therefore possible that the halo stars in the Milky Way formed out of gas that commonly exhibits DLA absorption at z>2.
479. Metallicities of GRB, DLA, and Ly{alpha} galaxies
ID:
ivo://CDS.VizieR/J/ApJ/683/321
Title:
Metallicities of GRB, DLA, and Ly{alpha} galaxies
Short Name:
J/ApJ/683/321
Date:
21 Oct 2021
Publisher:
CDS
Description:
We test the hypothesis that the host galaxies of long-duration gamma-ray bursts (GRBs) as well as quasar-selected damped Ly{alpha} (DLA) systems are drawn from the population of UV-selected star-forming, high-z galaxies (generally referred to as Lyman break galaxies). Specifically, we compare the metallicity distributions of the GRB and DLA populations against simple models where these galaxies are drawn randomly from the distribution of star-forming galaxies according to their star formation rate and HI cross section, respectively. We find that it is possible to match both observational distributions assuming very simple and constrained relations between luminosity, metallicity, and HI sizes. The simple model can be tested by observing the luminosity distribution of GRB host galaxies and by measuring the luminosity and impact parameters of DLA-selected galaxies as a function of metallicity. Our results support the expectation that GRB and DLA samples, in contrast with magnitude-limited surveys, provide an almost complete census of z~3 star-forming galaxies that are not heavily obscured.
480. Metallicities of Lyman limit systems and DLA
ID:
ivo://CDS.VizieR/J/ApJ/770/138
Title:
Metallicities of Lyman limit systems and DLA
Short Name:
J/ApJ/770/138
Date:
21 Oct 2021
Publisher:
CDS
Description:
We assess the metal content of the cool (~10^4^K) circumgalactic medium (CGM) about galaxies at z<~1 using an H I-selected sample of 28 Lyman limit systems (LLS; defined here as absorbers with 16.2<~logN_HI_<~18.5) observed in absorption against background QSOs by the Cosmic Origins Spectrograph on board the Hubble Space Telescope. The N_HI_ selection avoids metallicity biases inherent in many previous studies of the low-redshift CGM. We compare the column densities of weakly ionized metal species (e.g., O II, Si II, Mg II) to N_HI_ in the strongest H I component of each absorber. We find that the metallicity distribution of the LLS (and hence the cool CGM) is bimodal with metal-poor and metal-rich branches peaking at [X/H]=~-1.6 and -0.3 (or about 2.5% and 50% solar metallicities). The cool CGM probed by these LLS is predominantly ionized. The metal-rich branch of the population likely traces winds, recycled outflows, and tidally stripped gas; the metal-poor branch has properties consistent with cold accretion streams thought to be a major source of fresh gas for star forming galaxies. Both branches have a nearly equal number of absorbers. Our results thus demonstrate there is a significant mass of previously undiscovered cold metal-poor gas and confirm the presence of metal enriched gas in the CGM of z<~1 galaxies.