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1021. VLBI observations of 3C 279 at 230GHz
ID:
ivo://CDS.VizieR/J/ApJ/772/13
Title:
VLBI observations of 3C 279 at 230GHz
Short Name:
J/ApJ/772/13
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report results from five day very long baseline interferometry (VLBI) observations of the well-known quasar 3C 279 at 1.3mm (230GHz) in 2011. The measured nonzero closure phases on triangles including stations in Arizona, California, and Hawaii indicate that the source structure is spatially resolved. We find an unusual inner jet direction at scales of ~1pc extending along the northwest-southeast direction (P.A.=127{deg}+/-3{deg}), as opposed to other (previously) reported measurements on scales of a few parsecs showing inner jet direction extending to the southwest. The 1.3mm structure corresponds closely with that observed in the central region of quasi-simultaneous super-resolution Very Long Baseline Array images at 7mm. The closure phase changed significantly on the last day when compared with the rest of observations, indicating that the inner jet structure may be variable on daily timescales. The observed new direction of the inner jet shows inconsistency with the prediction of a class of jet precession models. Our observations indicate a brightness temperature of ~8x10^10^K in the 1.3mm core, much lower than that at centimeter wavelengths. Observations with better uv coverage and sensitivity in the coming years will allow the discrimination between different structure models and will provide direct images of the inner regions of the jet with 20-30{mu}as (5-7 light months) resolution.
1022. VLBI observations of NRAO 530 at 22, 43 and 86GHz
ID:
ivo://CDS.VizieR/J/MNRAS/418/2260
Title:
VLBI observations of NRAO 530 at 22, 43 and 86GHz
Short Name:
J/MNRAS/418/2260
Date:
21 Oct 2021
Publisher:
CDS
Description:
NRAO 530 is an optically violent variable source and has been studied with multi-epoch multifrequency high-resolution very long baseline interferometry (VLBI) observations. NRAO 530 was monitored with the Very Long Baseline Array (VLBA) at three frequencies (22, 43 and 86GHz) on 10 consecutive days in 2007 May during observations of the Galactic Centre (Sgr A*). Furthermore, analysis of archival data of NRAO 530 at 15GHz over the last 10 years allows us to study its detailed jet kinematics. We identified the compact component located at the southern-end of the jet as the VLBI core, consistent with previous studies.
1023. VLBI observations of southern ICRF sources
ID:
ivo://CDS.VizieR/J/AJ/127/3609
Title:
VLBI observations of southern ICRF sources
Short Name:
J/AJ/127/3609
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 8.4GHz very long baseline interferometry (VLBI) observations of 69 southern hemisphere extragalactic sources in the International Celestial Reference Frame. These are the first in a series of observations intended to image all such sources at milliarcsecond resolution in order to determine their continued suitability for reference-frame use based on intrinsic structure. We use the resultant images to calculate a core fraction, that is, the ratio of core flux density to total flux density, for all observed sources. The resulting distribution, with a mean value of 0.83, suggests that most sources are relatively compact. However, just over half the observed sources show significant extended emission in the form of multiple compact components. These sources are probably poorly suited for high-accuracy reference-frame use unless intrinsic structure and potential variability can be taken into account. Our observations represent the first large, comprehensive VLBI imaging survey in the southern hemisphere, significantly extending the existing limited VLBI surveys and, along with some well-known objects, containing many sources that have never been imaged at milliarcsecond resolution. The overlap with Very Long Baseline Array images of sources between 0{deg} and -35{deg} declination helps determine the limits to imaging with the southern hemisphere-accessible telescopes.
1024. VLBI polarimetry of CJF sources
ID:
ivo://CDS.VizieR/J/ApJ/589/733
Title:
VLBI polarimetry of CJF sources
Short Name:
J/ApJ/589/733
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Very Long Baseline Array observations and a statistical analysis of 5GHz VLBI polarimetry data from 177 sources in the Caltech-Jodrell Bank Flat-Spectrum (CJF) survey. The CJF survey, a complete, flux density-limited sample of 293 extragalactic radio sources, gives us the unique opportunity to compare a broad range of source properties for quasars, galaxies, and BL Lacertae objects. We focus primarily on jet properties, specifically, the correlation between the jet axis angle and the polarization angle in the core and jet. A strong correlation is found for the electric vector polarization angle in the cores of quasars to be perpendicular to the jet axis. Contrary to previous claims, no correlation is found between the jet polarization angle and the jet axis in either quasars or BL Lac objects. With this large, homogeneous sample we are also able to investigate cosmological issues and active galactic nucleus evolution.
1025. VLT Lyman-break galaxy redshift survey. II.
ID:
ivo://CDS.VizieR/J/MNRAS/414/28
Title:
VLT Lyman-break galaxy redshift survey. II.
Short Name:
J/MNRAS/414/28
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have measured redshifts for 243 z~~3 quasars in nine Very Large Telescope (VLT) Visible Imaging and Multi-Object Spectrograph (VIMOS) Lyman-break galaxy (LBG) redshift survey areas, each of which is centred on a known bright quasar. Using the spectra of these quasars, we measure the cross-correlation between neutral hydrogen gas causing the Ly{alpha} forest and 1020 LBGs at z~~3.
1026. VRc light curves of SBSG 1520+530
ID:
ivo://CDS.VizieR/J/A+A/440/53
Title:
VRc light curves of SBSG 1520+530
Short Name:
J/A+A/440/53
Date:
21 Oct 2021
Publisher:
CDS
Description:
The files table1.dat and table2.dat contain light curves of the double quasar SBS1520+530 obtained at Maidanak observatory from April 2003 to August 2004. table1.dat contains the R-band light curve. table2.dat contains the V-R light curve.
1027. VRI and K-band light curves of type 1 AGNs
ID:
ivo://CDS.VizieR/J/ApJ/886/150
Title:
VRI and K-band light curves of type 1 AGNs
Short Name:
J/ApJ/886/150
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a dust-reverberation survey of quasars at redshifts z<0.6. We found a delayed response of the K-band flux variation after the optical flux variation in 25 out of 31 targets, and obtained the lag time between them for 22 targets. Combined with the results for nearby Seyfert galaxies, we provide the largest homogeneous collection of K-band dust-reverberation data for 36 type 1 active galactic nuclei (AGNs). This doubles the sample and includes the most distant AGN and the largest lag so far measured. We estimated the optical luminosity of the AGN component of each target using three different methods: spectral decomposition, the flux-variation-gradient method, and image decomposition. We found a strong correlation between the reverberation radius for the innermost dust torus and the optical luminosity over a range of approximately four orders of magnitude in luminosity, as is already known for Seyfert galaxies. We estimated the luminosity distances of the AGNs based on their dust-reverberation lags, and found that the data in the redshift-distance diagram are consistent with the current standard estimates of the cosmological parameters. We also present the radius-luminosity relations for isotropic luminosity indicators such as the hard X-ray (14-195keV), [OIV]25.89{mu}m, and mid-infrared (12{mu}m) continuum luminosities, which are applicable to obscured AGNs.
1028. VRIJHK photometry of 3C 279
ID:
ivo://CDS.VizieR/J/AJ/151/54
Title:
VRIJHK photometry of 3C 279
Short Name:
J/AJ/151/54
Date:
21 Oct 2021
Publisher:
CDS
Description:
We searched for quasi-periodicities on year-like timescales in the light curves of six blazars in the optical--near-infrared bands and we made a comparison with the high energy emission. We obtained optical/NIR light curves from Rapid Eye Mounting photometry plus archival Small & Moderate Aperture Research Telescope System data and we accessed the Fermi light curves for the {gamma}-ray data. The periodograms often show strong peaks in the optical and {gamma}-ray bands, which in some cases may be inter-related. The significance of the revealed peaks is then discussed, taking into account that the noise is frequency dependent. Quasi-periodicities on a year-like timescale appear to occur often in blazars. No straightforward model describing these possible periodicities is yet available, but some plausible interpretations for the physical mechanisms causing periodic variabilities of these sources are examined.
1029. VRi light curves of the lensed QSO HE 0435-1223
ID:
ivo://CDS.VizieR/J/A+A/528/A42
Title:
VRi light curves of the lensed QSO HE 0435-1223
Short Name:
J/A+A/528/A42
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present VRi photometric observations of the quadruply imaged quasar HE0435-1223, carried out with the Danish 1.54m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as a function of time.
1030. VRI monitoring of the QSO 3C 273 in 2005-2016
ID:
ivo://CDS.VizieR/J/ApJS/229/21
Title:
VRI monitoring of the QSO 3C 273 in 2005-2016
Short Name:
J/ApJS/229/21
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have monitored the quasar 3C 273 in the optical V, R, and I bands from 2005 to 2016. Intraday variability (IDV) is detected on seven nights. The variability amplitudes on most of the nights are less than 10%, and on four nights, more than 20%. When considering the nights with time spans >4hr, the duty cycle (DC) is 14.17%. Over the 12yrs, the overall magnitude and color index variabilities are {Delta}I=0.67, {Delta}R=0.72, {Delta}V=0.68, and {Delta}(V-R)=0.25, respectively. The largest clear IDV has an amplitude of 42% over just 5.8 minutes, and the weakest detected IDV is 5.4% over 175 minutes. The BWB (bluer when brighter) chromatic trend is dominant for 3C 273 and appears at different flux levels on intraday timescales. The BWB trend exists for short-term timescales and intermediate-term timescales but different timescales have different correlations. There is no BWB trend for our whole time-series data sets. A significant anticorrelation between the BWB trend and length of timescales is found. Combining with V-band data from previous works, we find a possible quasi-periodicity of P=3918+/-1112 days. The possible explanations for the observed variability, BWB chromatic trend, and periodicity are discussed.