A5042348372- Geophysics and Gravity Measurements
- GNSS positioning and interference
- Radio Astronomy Observations and Technology
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Ionosphere and magnetosphere dynamics
- History and Developments in Astronomy
- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Pulsars and Gravitational Waves Research
- Galaxies: Formation, Evolution, Phenomena
- Historical Astronomy and Related Studies
- Gamma-ray bursts and supernovae
- Statistical and numerical algorithms
- Inertial Sensor and Navigation
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- Geochemistry and Geologic Mapping
- Calibration and Measurement Techniques
- Advanced Frequency and Time Standards
- Methane Hydrates and Related Phenomena
- Cosmology and Gravitation Theories
- Geological and Geophysical Studies
- Astro and Planetary Science
Geoscience Australia
2015-2024
Konkoly Observatory
2023
Research Centre for Astronomy and Earth Sciences
2023
Eötvös Loránd University
2023
Burdenko Neurosurgery Institute
2022
Technische Universität Berlin
2022
GFZ Helmholtz Centre for Geosciences
2022
Aalto University
2022
St Petersburg University
2000-2014
Auckland University of Technology
2010
We present the second realization of International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years Very Long Baseline Interferometry observations.ICRF2 contains precise positions 3414 compact astronomical objects and has a positional noise floor ∼40 μas directional stability frame axes ∼10 μas.A set 295 new "defining" sources was selected on basis lack extensive intrinsic source structure.The these defining their more uniform sky distribution eliminates two...
ABSTRACT Six very successful Very Long Baseline Array (VLBA) calibrator survey campaigns were run between 1994 and 2007 to build up a large list of compact radio sources with positions precise enough for use as long baseline interferometry (VLBI) phase reference calibrators. We report on the results second epoch VLBA Calibrator Survey campaign (VCS-II) in which 2400 VCS re-observed X S bands order improve upcoming third realization International Celestial Reference Frame (ICRF3) well their...
A new realization of the International Celestial Reference Frame (ICRF) is presented based on work achieved by a working group Astronomical Union (IAU) mandated for this purpose. This follows initial ICRF completed in 1997 and its successor, ICRF2, adopted as replacement 2009. The frame, referred to ICRF3, nearly 40 years data acquired very long baseline interferometry at standard geodetic astrometric radio frequencies (8.4 2.3 GHz), supplemented with collected higher (24 GHz dual-frequency...
While analyzing decades of very long baseline interferometry (VLBI) data, we detected the secular aberration drift extragalatic radio source proper motions caused by rotation Solar System barycenter around Galactic center. Our results agree with predicted estimate to be 4-6 micro arcseconds per year ({\mu}as/yr) towards {\alpha} = 266\circ and {\delta} -29\circ. In addition, tried detect quadrupole systematics velocity field. The analysis method consisted three steps. First, analyzed...
High-redshift radio-loud quasars are used to, among other things, test the predictions of cosmological models, set constraints on black hole growth in early Universe and understand galaxy evolution. Prior to this paper, 20 extragalactic radio sources at redshifts above 4.5 have been imaged with very long baseline interferometry (VLBI). Here, we report observations an additional ten z > 1.7 5 GHz European VLBI Network, thereby increasing number by 50 per cent. Combining our newly observed...
We propose new estimates of the secular aberration drift, mainly due to rotation Solar System about Galactic center, based on up-to-date VLBI observations and improved method outlier elimination. fit degree-2 vector spherical harmonics extragalactic radio source proper motion field derived from geodetic spanning 1979-2013. pay particular attention elimination procedure remove outliers (i) coordinate time series (ii) sample. obtain more accurate values system acceleration compared those in...
Many of the compact extragalactic radio sources that are used as fiducial points to define celestial reference frame known have proper motions detectable with long-term geodetic/astrometric very long baseline interferometry (VLBI) measurements. These changes can be high several hundred microarcseconds per year for certain objects. When imaged VLBI at milliarcsecond (mas) angular resolution, these (radio-loud active galactic nuclei) typically show structures dominated by a compact, often...
<i>Context. <i/>Information on physical characteristics of astrometric radio sources, such as magnitude and redshift, is great importance for many astronomical studies. However, data usually used in astrometry often incomplete outdated.<i>Aims. <i/>Our purpose to study the optical more than 4000 sources observed by VLBI technique since 1979. We also studied effect asymmetry distribution reference correlation matrices between vector spherical harmonics first second degrees.<i>Methods. <i/>The...
The AUSTRAL observing program was started in 2011, performing geodetic and astrometric very long baseline interferometry (VLBI) sessions using the new Australian AuScope VLBI antennas at Hobart, Katherine, Yarragadee, with contribution from Warkworth (New Zealand) 12 m Hartebeesthoek (South Africa) 15 to make a southern hemisphere array of telescopes similar design capability. Designed style next-generation system, these small fast allow for way observing, comprising higher data rates more...
Astrometric positions of radio-emitting active galactic nuclei (AGNs) can be determined with sub-milliarcsec accuracy using very long baseline interferometry (VLBI). The usually small apparent proper motion distant extragalactic targets allow us to realize the fundamental celestial reference frame VLBI observations. However, long-term astrometric monitoring may reveal extreme changes in some AGN positions. Using new observations 2018-2021, we show here that four radio sources (3C48, CTA21,...
Abstract Radio-loud quasars at high redshift ( z ≥ 4) are rare objects in the universe and rarely observed with Very Long Baseline Interferometry (VLBI). But some of them have flux density sufficiently for monitoring their apparent position. The instability astrometric positions could be linked to astrophysical process jetted active galactic nuclei early universe. Regular observations high-redshift used estimating proper motion over several years. We undertaken regular VLBI 2.3 GHz S band)...
ABSTRACT There is still a limited number of high-redshift (z &gt; 3) active galactic nuclei (AGNs) whose jet kinematics have been studied with very long baseline interferometry (VLBI). Without dedicated proper motion survey, regularly conducted astrometric VLBI observations bright radio-emitting AGN sensitive arrays can be utilized to follow changes in the jets, by means high-resolution imaging and brightness distribution modelling. Here, we present first-time kinematic study NVSS...
We present the results of spectroscopic observations optical counterparts 47 southern radio sources from candidate International Celestial Reference Catalogue (ICRC), as part a Very Long Baseline Interferometry (VLBI) program to strengthen celestial reference frame, especially in south. The were made with 3.58-meter European Southern Observatory New Technology Telescope (NTT). obtained redshifts for 30 quasars and one galaxy, further 7 objects being probable BL Lac featureless spectra. Of...
Continuing our program of spectroscopic observations International Celestial Reference Frame (ICRF) sources, we present redshifts for 120 quasars and radio galaxies. Data were obtained with five telescopes: the 3.58 m European Southern Observatory New Technology Telescope, two 8.2 Gemini telescopes, 2.5 Nordic Optical Telescope (NOT), 6.0 Big Azimuthal Special Astrophysical in Russia. The targets selected from VLBI Service Geodesy & Astrometry candidate Catalog which forms part an...
The gravitational attraction of the Galactic centre leads to centrifugal acceleration Solar system barycentre. It results in secular aberration drift which displaces position distant radio sources. effect should be accounted for high-precision astrometric reductions as well by corresponding update ICRS definition.
Context. Radio-loud active galactic nuclei in the early Universe are rare. The quasars J0906+6930 at redshift z=5.47 and J2102+6015 z=4.57 stand out from known sample with their compact emission on milliarcsecond (mas) angular scale high (0.1-Jy level) flux densities measured GHz radio frequencies. This makes them ideal targets for very long baseline interferometry (VLBI) observations. Aims. By means of VLBI imaging we can reveal inner structure model brightness distribution to better...
Context. The link of the Gaia frame in terms non-rotation with respect to International Celestial Reference System (ICRS), which is realized via very long baseline interferometry (VLBI) at radio wavelengths, has be conducted for wide range optical magnitudes spacecraft observes. There a sufficient number suitable counterparts between two measurement systems optically faint objects. However, common bright ( G ≤ 13 mag) objects sparse as most are frequencies, and only few astrometry have been...
Context. We highlight the capabilities of geodetic VLBI technique to test General relativity in classical astrometric style, i.e., measuring deflection light vicinity Sun. Aims. In previous studies, parameter was estimated by global analyses thousands sessions. Here we estimate from a single session where Sun has approached two strong reference radio sources 0229+131 and 0235+164 at an elongation angle 1-3 degrees. Methods. The AUA020 1 May 2017 designed obtain more than 1000 group delays...
We propose an alternative method to detect the secular aberration drift induced by solar system acceleration due attraction Galaxy centre. This is free of individual radio source proper motion caused intrinsic structure variation. developed a procedure estimate scale factor directly from very long baseline interferometry (VLBI) data analysis in source-wise mode within global solution. The estimated for each reference individually as function astrometric coordinates (right ascension and...