Search

Start Over Subject quasars Content Level Research
491. 144MHz radio fluxes of z>5 quasars
ID:
ivo://CDS.VizieR/J/A+A/656/A137
Title:
144MHz radio fluxes of z>5 quasars
Short Name:
J/A+A/656/A137
Date:
17 Mar 2022 14:39:39
Publisher:
CDS
Description:
Optically luminous quasars at z>5 are important probes of super-massive black hole (SMBH) formation. With new and future radio facilities, the discovery of the brightest low-frequency radio sources in this epoch would be an important new probe of cosmic reionization through 21-cm absorption experiments. We present the result of a study of the low-frequency radio properties of a sample of 115 known spectroscopically confirmed z>5 quasars using the second data release of the Low Frequency Array (LOFAR) Two Meter Sky survey (LoTSS-DR2), reaching noise levels of 80uJy/beam (at 144MHz) over an area of 5720 square degrees. We find that 41 sources (36%) are detected in LoTSS-DR2 at >2{sigma} significance and we explore the evolution of their radio properties (power, spectral index, and radio loudness) as a function of redshift and rest-frame ultra-violet properties.
492. Michigan Emission-Line Objects
ID:
ivo://CDS.VizieR/VII/171
Title:
Michigan Emission-Line Objects
Short Name:
VII/171
Date:
21 Oct 2021
Publisher:
CDS
Description:
The objects of this catalogue were detected by using the 61-cm aperture Curtis Schmidt telescope in combination with a thin objective prism (1.8{deg}) at the Cerro Tololo Inter-American Observatory. The low-dispersion spectra (174nm/mm at H{beta}) cover the wavelength range between 5350 and 3400 {AA}, where the emission lines such that those of [OII], [OIII] and Ly{alpha} are visible. The objects could be detected up to 18th magnitude. Note that the list archived here is not the same as the published lists (see the "References" section below): the positions in the "catalog.dat" file are generally more accurate than those in the original publication and the origin for these is not known. In the printed lists of papers , information presented for each object also includes image dimensions from the Palomar Observatory Sky Survey, an estimated continuum apparent magnitude, a redshift estimate when feasible, or (for galaxies) a spectral classification which involves compactness, color, and line-strength parameters.
493. Microlensing maps for a cusp configuration
ID:
ivo://CDS.VizieR/J/A+A/553/A53
Title:
Microlensing maps for a cusp configuration
Short Name:
J/A+A/553/A53
Date:
21 Oct 2021
Publisher:
CDS
Description:
We provide the microlensing maps generated to study microlensing in the mid-infrared range for a cusp-configuration lensed AGN. The maps provided correspond to images which are respectively saddle-point and minimum of the arrival time surface. We also provide simulated images of sources with a disc-like brightness profile or a ring-like brightness profile corresponding to an accretion disc or a torus brightness distribution. These source profiles should be convolved with microlensing maps of the same spatial resolution to simulate microlensing of the corresponding source and generate probability density function (PDF) of microlensing similar to those shown in Figures 3,4,5,8. These maps can also be used to generate synthetic microlensing lightcurves (Figure 9) or derive PDF for the Rcusp relation (Figure 10).
494. Microquasar candidates
ID:
ivo://CDS.VizieR/J/A+A/477/125
Title:
Microquasar candidates
Short Name:
J/A+A/477/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
Microquasars are ideal natural laboratories for understanding accretion/ejection processes, studying the physics of relativistic jets, and testing gravitational phenomena. Nevertheless, these objects are difficult to find in our Galaxy. The main goal of this work is to increase the number of known systems of this kind, which should allow better testing of high-energy phenomena and more realistic statistical studies of this galactic population to be made. We have developed an improved search strategy based on positional cross-identification with very restrictive selection criteria to find new MQs, taking advantage of more sensitive modern X-ray data. To do this, we made combined use of the radio, infrared, and X-ray properties of the sources, using different available catalogs.
495. Mid-IR QSO spectral templates
ID:
ivo://CDS.VizieR/J/MNRAS/438/2317
Title:
Mid-IR QSO spectral templates
Short Name:
J/MNRAS/438/2317
Date:
21 Oct 2021
Publisher:
CDS
Description:
Mid-infrared (MIR) quasar spectra exhibit a suite of emission features including high ionization coronal lines from the narrow-line region illuminated by the ionizing continuum, broad dust bumps from silicates and graphites, and polycyclic aromatic hydrocarbon (PAH) features from star formation in the host galaxy. However, in Spitzer Infared Spectrograph (IRS) data, few features are detected in most individual spectra because of typically low signal-to-noise ratios (S/N). By generating spectral composites from over 180 IRS observations of Sloan Digital Sky Survey broad-line quasars, we boost the S/N and reveal features in the complex spectra that are otherwise lost in the noise. In addition to an overall composite, we generate composites in three different luminosity bins that span the range of 5.6{mu}m luminosities of 10^40^-10^46^ (erg/s). We detect the high-ionization, forbidden emission lines of [SIV], [OIV] and [NeV] {lambda}14um in all templates and PAH features in all but the most luminous template.
496. Millimeter continuum of extragal. sources III.
ID:
ivo://CDS.VizieR/J/A+AS/102/611
Title:
Millimeter continuum of extragal. sources III.
Short Name:
J/A+AS/102/611
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
497. MIR-selected quasar parameters
ID:
ivo://CDS.VizieR/J/ApJ/791/113
Title:
MIR-selected quasar parameters
Short Name:
J/ApJ/791/113
Date:
21 Oct 2021
Publisher:
CDS
Description:
We provide a catalog of 391 mid-infrared-selected (MIR; 24 {mu}m) broad-emission-line (BEL; type 1) quasars in the 22 deg^2^ SWIRE Lockman Hole field. This quasar sample is selected in the MIR from Spitzer MIPS with S_24_> 400 {mu}Jy, jointly with an optical magnitude limit of r(AB) < 22.5 for broad line identification. The catalog is based on MMT and Sloan Digital Sky Survey (SDSS) spectroscopy to select BEL quasars, extending the SDSS coverage to fainter magnitudes and lower redshifts, and recovers a more complete quasar population. The MIR-selected quasar sample peaks at z ~ 1.4 and recovers a significant and constant (20%) fraction of extended objects with SDSS photometry across magnitudes, which were not included in the SDSS quasar survey dominated by point sources. This sample also recovers a significant population of z < 3 quasars at i > 19.1. We then investigate the continuum luminosity and line profiles of these MIR quasars, and estimate their virial black hole masses and the Eddington ratios. The supermassive black hole mass shows evidence of downsizing, although the Eddington ratios remain constant at 1 < z < 4. Compared to point sources in the same redshift range, extended sources at z < 1 show systematically lower Eddington ratios. The catalog and spectra are publicly available online.
498. mm-monitoring of radio sources IV.
ID:
ivo://CDS.VizieR/J/A+AS/122/271
Title:
mm-monitoring of radio sources IV.
Short Name:
J/A+AS/122/271
Date:
21 Oct 2021
Publisher:
CDS
Description:
Radio flux densities are presented for 118 extragalactic radio sources monitored at 90, 142 and 230GHz with the IRAM 30m telescope during 1993-1994. For the most frequently observed sources we show light curves including 30 m-measurements published in previous papers, Steppe et al. (1988A&AS...75..317S; 1992A&AS...96..441S and and 1993, Cat. <J/A+AS/102/611>)
499. 7mm spectral survey of PKS 1830-211
ID:
ivo://CDS.VizieR/J/A+A/535/A103
Title:
7mm spectral survey of PKS 1830-211
Short Name:
J/A+A/535/A103
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a wide 7mm spectral survey of molecular absorption lines arising in the disk of a z=0.89 spiral galaxy located in front of the quasar PKS 1830-211. The survey was done with the Australia Telescope Compact Array and covers the frequency interval 30-50GHz, corresponding to the rest-frame frequency interval 57-94GHz. A total of 28 different species, plus 8 isotopic variants, were detected toward the South-West absorption, located at about 2kpc from the center of the z=0.89 galaxy, which makes it the extragalactic object with the largest number of detected molecular species so far.
500. MOJAVE IX. Core shift effects
ID:
ivo://CDS.VizieR/J/A+A/545/A113
Title:
MOJAVE IX. Core shift effects
Short Name:
J/A+A/545/A113
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have investigated a frequency-dependent shift in the absolute position of the optically thick apparent origin of parsec-scale jets ("core shift" effect) to probe physical conditions in ultra-compact relativistic outflows in active galactic nuclei. We used multi-frequency Very Long Baseline Array (VLBA) observations of 191 sources carried out in 12 epochs in 2006 within the Monitoring Of Jets in Active galactic nuclei with VLBA Experiments (MOJAVE) program. The observations were performed at 8.1, 8.4, 12.1, and 15.4GHz. We implemented a method of determining the core shift vector based on (i) image registration by two-dimensional normalized cross-correlation and (ii) model-fitting the source brightness distribution to take into account a non-zero core component offset from the phase center.