Related papers: Astrometric suitability of optically-bright ICRF s…
We present the results of spectroscopic observations of the optical counterparts of 47 southern radio sources from the candidate International Celestial Reference Catalogue (ICRC), as part of a Very Long Baseline Interferometry (VLBI)…
The International Celestial Reference Frame (ICRF, Ma et al. 1998) is currently the best realization of a quasi-inertial reference system. It is based on more than 10 years of cumulated geodetic and astrometric VLBI observations of compact…
Four close radio sources in the International Celestial Reference Frame (ICRF) catalog were observed using phase referencing with the VLBA at 43, 23 and 8.6 GHz, and with VERA at 23 GHz over a one year period. The goal was to determine the…
Previous studies based on the latest realisation of the International Celestial Reference Frame (ICRF3) have suggested a correlation between astrometric properties (such as the radio-optical offset) and redshift for active galactic nuclei…
The large number and all-sky distribution of quasars from different surveys, along with their presence in large, deep astrometric catalogs,enables the building of an optical materialization of the ICRS following its defining principles.…
Between 1997 and 2004 several observing runs were conducted mainly with the CTIO 0.9 m to image ICRF counterparts (mostly QSOs) in order to determine accurate optical positions. Contemporary to these deep CCD images the same fields were…
Context. We present a celestial reference frame (CRF) based on the combination of independent, multifrequency radio source position catalogs using nearly 40 years of Very Long Baseline Interferometry observations at the standard geodetic…
With Gaia, it will become possible to directly link the radio and optical reference frames using a large number of common objects. For the most accurate radio-optical link, it is important to know the level of spatial coincidence between…
Precision geodesy relies on the stability of the International Celestial Reference Frame (ICRF), yet its reference sources, Active Galactic Nuclei (AGN), exhibit changes in source structure that can manifest as apparent shifts in their…
The highly-accurate optical reference frame GCRF (Gaia Celestial Reference Frame) is expected to be available in several years. By the same time, a new version of radio reference frame ICRF (International Celestial Reference Frame) will be…
Gaia-CRF3 is the celestial reference frame for positions and proper motions in the third release of data from the Gaia mission, Gaia DR3 (and for the early third release, Gaia EDR3, which contains identical astrometric results). The…
We aim to evaluate the possibility of improving the ICRS realization starting from the ICRF2 catalogue by investigating the coordinate time series of radio sources observed by VLBI between 1979 and 2016. Sources with long observational…
A new list of physical characteristics of 3914 astrometric radio sources, including all 717 ICRF-Ext.2 sources, observed during IVS and NRAO VCS sessions have been compiled. The list includes source type, redshift and visual magnitude (if…
There exist inconsistencies between the bright and faint Gaia Celestial Reference Frame 3 (Gaia-CRF3), which manifests as a systematic rotation and needs to be independently estimated then corrected in future data releases. We collected 64…
A new list of physical characteristics of 4261 astrometric radio sources, including all 717 ICRF-Ext.2 sources has been compiled. Comparison of our data of optical characteristics with the official International Earth Rotation and Reference…
The VLBI USNO 2016A (U16A) solution is part of a work-in-progress effort by USNO towards the preparation of the ICRF3. Most of the astrometric improvement with respect to the ICRF2 is due to the re-observation of the VCS sources. Our…
We extend previous works by considering two additional radio frequencies (K band and X/Ka band) with the aim to study the frequency dependence of the source positions and its potential connection with the physical properties of the…
We present the first high-precision proper motion catalog, tied to the International Celestial Reference System (ICRS), of infrared astrometric reference stars within R $\leq$ 25" (1 pc) of the central supermassive black hole at the…
We aim to investigate the overall properties of the ICRF3 with the help of the Gaia Data release 2 (Gaia DR2). This could serve as an external check of the quality of the ICRF3. The radio source positions of the ICRF3 catalog were compared…
Context: We introduce the computation of global reference frames from Very Long Baseline Interferometry (VLBI) observations at the Vienna International VLBI Service for Geodesy and Astrometry (IVS) Analysis Center (VIE) in detail. We focus…