Search

Start Over Subject radio astronomy
1861. VLBI observations of BL Lac objects
ID:
ivo://CDS.VizieR/J/A+A/466/63
Title:
VLBI observations of BL Lac objects
Short Name:
J/A+A/466/63
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present EVN observations of seven BL Lac objects selected from the RGB sample. To investigate the intrinsic radiation property of BL Lac objects, we estimated the Doppler factor with the VLA or MERLIN core and the total 408MHz luminosity for a sample of 170 BL Lac objects. The intrinsic (comoving) synchrotron peak frequency was then calculated by using the estimated Doppler factor. Assuming a Lorentz factor of 5, the viewing angle of jets was constrained. The high-resolution VLBI images of seven sources all show a core-jet structure. We estimated the proper motions of three sources with the VLBI archive data, and find that the apparent speed increases with the distance of components to the core for all of them.
1862. 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.
1863. 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.
1864. 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.
1865. VLBI Position Measurements
ID:
ivo://CDS.VizieR/J/AZh/81/1032
Title:
VLBI Position Measurements
Short Name:
J/AZh/81/1032
Date:
21 Oct 2021
Publisher:
CDS
Description:
A large number (~2 million) of VLBI observations have been reduced in order to re ne the measured coordinates of the observed radio sources. The data reduction was carried out in the OCCAM package using the least squares colocation method. Corrections to the coordinates of 642 objects were derived. The accuracy of the catalog is no worse than 0.2 milliseconds of arc for stable sources.
1866. VLBI suvey around B0218+357 at 90cm
ID:
ivo://CDS.VizieR/J/ApJ/673/78
Title:
VLBI suvey around B0218+357 at 90cm
Short Name:
J/ApJ/673/78
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the first wide-field, very long baseline interferometry (VLBI) survey at 90cm. The survey area consists of two overlapping 28deg^2^ fields centered on the quasar J0226+3421 and the gravitational lens B0218+357. A total of 618 sources were targeted in these fields, based on identifications from Westerbork Northern Sky Survey (WENSS) data. Of these sources, 272 had flux densities that, if unresolved, would fall above the sensitivity limit of the VLBI observations. A total of 27 sources were detected as far as 2{deg} from the phase center. The results of the survey suggest that at least 10% of moderately faint (S~100mJy) sources found at 90 cm contain compact components smaller than ~0.1"-0.3" and stronger than 10% of their total flux densities.
1867. VRI observations of radio source S5 0716+71
ID:
ivo://CDS.VizieR/J/AZh/84/885
Title:
VRI observations of radio source S5 0716+71
Short Name:
J/AZh/84/885
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of VRI photometry of the gravitationally lensed system Q2237+0305 carried out on the 1.5-m telescope of Maidanak observatory in 2004-2005 are presented. The distance between the components is of the order of 1".
1868. VSOP 5 GHz AGN Survey. III
ID:
ivo://CDS.VizieR/J/ApJS/155/33
Title:
VSOP 5 GHz AGN Survey. III
Short Name:
J/ApJS/155/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VLBI Space Observatory Programme (VSOP) mission is a Japanese-led project to study radio sources with sub-milliarcsec resolution using an orbiting 8m telescope, HALCA, along with global arrays of Earth-based telescopes. Approximately 25% of the observing time is devoted to a survey of compact active galactic nuclei (AGNs) that are stronger than 1Jy at 5GHz - the VSOP AGN Survey. This paper, the third in the series, presents the results from the analysis of the first 102 Survey sources.
1869. VSOP 5GHz AGN Survey. IV
ID:
ivo://CDS.VizieR/J/ApJ/616/110
Title:
VSOP 5GHz AGN Survey. IV
Short Name:
J/ApJ/616/110
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VLBI Space Observatory Programme (VSOP) mission is a Japanese-led project to study radio sources with submilliarcsecond angular resolution, using an orbiting 8m telescope on board the satellite HALCA with a global Earth-based array of telescopes. A major program is the 5GHz VSOP Survey Program, which we supplement here with Very Long Baseline Array observations to produce a complete and flux density-limited sample. Using statistical methods of analysis of the observed visibility amplitude versus projected (u, v) spacing, we have determined the angular size and brightness temperature distribution of bright radio emission from active galactic nuclei.
1870. VSOP 5GHz AGN survey V.
ID:
ivo://CDS.VizieR/J/ApJS/175/314
Title:
VSOP 5GHz AGN survey V.
Short Name:
J/ApJS/175/314
Date:
21 Oct 2021
Publisher:
CDS
Description:
In 1997 February, the Japanese radio astronomy satellite HALCA was launched to provide the space-bourne element for the VLBI Space Observatory Program (VSOP) mission. Approximately 25% of the mission time was dedicated to the VSOP survey of bright compact active galactic nuclei (AGNs) at 5GHz. This paper, the fifth in the series, presents images and models for the remaining 140 sources not included in the third paper in the series, which contained 102 sources. For most sources, the plots of the (u,v) coverage, the visibility amplitude versus (u,v) distance, and the high-resolution image are presented. Model fit parameters to the major radio components are determined, and the brightness temperature of the core component for each source is calculated. The brightness temperature distributions for all of the sources in the VSOP AGN survey are discussed.