相关论文: Radio astrometry with chromatic AGN core positions
NRAO 530 is an optically violent variable source and has been studied with multi-epoch multi-frequency high-resolution VLBI observations. NRAO 530 was monitored with the VLBA at three frequencies (22, 43 and 86 GHz) on 10 consecutive days…
Geodetic Very Long Baseline Interferometry (VLBI) data are capable of measuring the light deflection caused by the gravitational field of the Sun and large planets with high accuracy. The parameter $\gamma$ of the parametrized…
Compact galactic and extragalactic radio sources can be imaged with an unsurpassed angular resolution of a few ten micro-arcseconds, adopting the observing technique of global millimeter VLBI. Here we present the Global Millimeter VLBI…
Astrometric accuracy of complex modern VLBI arrays cannot be calculated analytically. We study the astrometric accuracy of phase-referenced VLBI observations for the VLBA, EVN and global VLBI array by simulating VLBI data for targets at…
Very Long Baseline Interferometry (VLBI) observations can provide the position of compact radio sources with an accuracy of order 50 micro-arcseconds. This is sufficient to measure the trigonometric parallax and proper motions of any object…
We report on an ongoing effort to image active galactic nuclei simultaneously observed at 2.3 and 8.6 GHz in the framework of a long-term VLBI project RDV (Research and Development - VLBA) started in 1994 aiming to observe compact…
We have performed a very long baseline interferometry (VLBI) survey of local (z < 0.05) ultra hard X-ray (14-195 keV) selected active galactic nuclei (AGN) from the Swift Burst Alert Telescope (BAT) using KVN, KaVA, and VLBA. We first…
The core shift method is a powerful method to estimate the physical parameters in relativistic jets from active galactic nuclei. The classical approach assumes a conical geometry of a jet and a constant plasma speed. However, recent…
Only in the radio-loud population of active galactic nuclei (AGN) does the production, collimation, and acceleration of powerful relativistic jets take place. We introduce here a concept of combined VLBI- and X-ray spectroscopic…
We present a summary of the observation strategy of TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry), a monitoring program to study the parsec-scale structure and dynamics of relativistic jets in active…
The K\"onigl inhomogeneous jet model is applied to investigate the properties of the jets in Active Galactic Nuclei (AGNs). A sample of the AGNs is collected, in which the measurements of the angular size and radio flux density of the VLBI…
Results of high-resolution simultaneous multi-frequency 8.1-15.4 GHz VLBA polarimetric observations of relativistic jets in active galactic nuclei (the MOJAVE-2 project) are analyzed. We compare characteristics of VLBI features with jet…
One major problem of phase-referencing VLBI observations are phase errors due to the unknown tropospheric zenith delay at each antenna. These errors degrade the quality of the phase-referenced image and limit the achievable astrometric…
We conducted 22~GHz 1" JVLA imaging of 100 radio-quiet X-ray selected AGN from the Swift-BAT survey. We find AGN-driven kiloparsec-scale radio structures inconsistent with pure star formation in 11 AGN. The host galaxies of these AGN lie…
We analytically model stationary and axisymmetric active galactic nucleus jets, assuming energy conservation along each magnetic flux tube. Using very-long-baseline interferometry (VLBI) observations and published general relativistic…
Very Long Baseline Interferometric (VLBI) observations of quasar jets enable one to measure many theoretically expected effects. Estimating the significance of observational findings is complicated by the correlated noise in the image…
We investigate the hypothesis that {\gamma}-ray-quiet AGN have a larger tendency for jet bending than {\gamma}-ray-loud AGN, revisiting the analysis of Tingay, Murphy & Edwards (1998). We perform a statistical analysis using a large sample…
Radio galaxies are relatively faint at $\gamma$-ray energies, where they make up only 1-2% of all AGN detected by Fermi-LAT. However, they offer a unique perspective to study the intrinsic properties of AGN jets. For this reason, the…
High redshift active galactic nuclei (AGN) provide key insights into early supermassive black hole growth and cosmic evolution. This study investigates the parsec-scale properties of 86 radio-loud quasars at z $\geq$ 3 using very long…
Some models of the expanding Universe predict that the astrometric proper motion of distant radio sources embedded in space-time are non-zero as radial distance from observer to the source grows. Systematic effects due to this proper motion…