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The alignment between the radio-based International Celestial Reference Frame (ICRF) and the optical Gaia Celestial Reference Frame (Gaia-CRF) is critical for multi-waveband astronomy, yet systematic offsets at the optical bright end (G<13)…

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…

Astrophysics · Physics 2008-12-31 A. B. Pushkarev , Y. Y. Kovalev , A. P. Lobanov

Very Long Baseline Interferometry (VLBI) offers unrivalled resolution in studies of celestial radio sources. The subjects of interest of the IAU Symposium No. 356, the Active Galactic Nuclei (AGN) of all types, constitute the major…

Instrumentation and Methods for Astrophysics · Physics 2021-02-03 Leonid I. Gurvits , Robert Beswick , Melvin Hoare , Ann Njeri , Jay Blanchard , Carla Sharpe , Adrian Tiplady , Aletha de Witt

The Gaia celestial reference frame (Gaia-CRF) will benefit from a close assessment with independent methods, such as Very Long Baseline Interferometry (VLBI) measurements of radio stars at bright magnitudes. However, obtaining full…

Instrumentation and Methods for Astrophysics · Physics 2024-03-27 Jingdong Zhang , Bo Zhang , Shuangjing Xu , Niu Liu , Wen Chen , Hao Ding , Pengfei Jiang , Yan Sun , Jinqing Wang , Lang Cui , Shiming Wen , Xiaofeng Mai , Jinling Li , Fengchun Shu , Yidan Huang

We have conducted a deep, very long baseline interferometry (VLBI) observation at 1.4 GHz of an area of sky located within the NOAO Bootes field, using the NRAO VLBA and 100-m Green Bank Telescope. Applying wide-field VLBI techniques, a…

Astrophysics · Physics 2009-11-10 M. A. Garrett , J. M. Wrobel , R. Morganti

We study the faint radio population using wide-field very long baseline interferometry (VLBI) observations of 2865 known radio sources in the Cosmic Evolution Survey (COSMOS) field. The main objective of the project was to determine where…

Vision foundation models have been shown to be effective at processing satellite imagery into representations fit for downstream tasks, however, creating models which operate over multiple spatial resolutions and modes is challenging. This…

Computer Vision and Pattern Recognition · Computer Science 2026-04-14 Patrick Kage , Pavlos Andreadis

Global VLBI observations at 5 GHz have been performed to study the source morphology in 10 compact steep-spectrum (CSS) sources selected from the Peacock & Wall catalogue with the aim of finding asymmetric structures produced by the…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 D. Dallacasa , M. Orienti , C. Fanti , R. Fanti , C. Stanghellini

The results of VLBI total intensity (I) and linear polarization (P) observations at 6cm are presented for ten radio bright BL Lacertae objects. These images complete first-epoch polarization observations for the 1-Jy sample of northern BL…

Astrophysics · Physics 2009-11-10 D. C. Gabuzda , A. B. Pushkarev , T. V. Cawthorne

We have studied Very Long Baseline Array (VLBA) polarimetric observations of 8 sources including quasars and BL Lacs at 12, 15, 22, 24 and 43 GHz and high frequency rotation measure ($RM$) maps are presented. We find typical values for the…

High Energy Astrophysical Phenomena · Physics 2015-06-12 J. C. Algaba

We demonstrate that at 1.4 GHz the combined response of sources detected serendipitously in deep, wide-field VLBI images is sufficient to permit self-calibration techniques to be employed. This technique of "full-beam" VLBI self-calibration…

Astrophysics · Physics 2007-05-23 M. A. Garrett , J. M. Wrobel , R. Morganti

We are in the process of obtaining VLBA polarisation data for the 135 MOJAVE-I Active Galactic Nuclei at four wavelengths in the 18-22cm band. These observations will enable studies of the evolution of the intensity and magnetic-field…

Cosmology and Nongalactic Astrophysics · Physics 2011-02-01 Colm Coughlan , Ronan Murphy , Kyle Mc Enery , Heather Patrick , Redmond Hallahan , Denise Gabuzda

The East-Asian VLBI Network (EAVN) is the international VLBI facility in East Asia and is conducted in collaboration with China, Japan, and Korea. The EAVN consists of VLBI arrays operated in each East Asian country, containing 21 radio…

We present the results of comparative study of amplitude calibrations for East-Asia VLBI Network (EAVN) at 22 and 43 GHz using two different methods of an "a-priori" and a "template spectrum", particularly on lower declination sources.…

Millimetre-VLBI is an important tool in AGN astrophysics, but it is limited by short atmospheric coherence times and poor receiver and antenna performance. We demonstrate a new kind of phase referencing for the VLBA, enabling us to increase…

Astrophysics · Physics 2007-05-23 E. Middelberg , A. L. Roy , R. C. Walker , H. Falcke , T. P. Krichbaum

At 147 GHz (2mm wavelength), we detected three prominent AGN (NRAO150, 3C279, 1633+382) with Very Long Baseline Interferometry (VLBI) with an angular resolution of only 18 micro-arcseconds on the baseline between two antennas in Arizona…

Very-long-baseline interferometry (VLBI) is a challenging observational technique, which requires in-depth knowledge about radio telescope instrumentation, interferometry, and the handling of noisy data. The reduction of the raw data is…

Instrumentation and Methods for Astrophysics · Physics 2022-09-14 Michael Janssen , Jack F. Radcliffe , Jan Wagner

Dual active galactic nuclei (DAGN) and supermassive black hole binaries (SMBHBs) at kpc and pc-scale separations, respectively, are expected during stages of galaxy merger and evolution. Their observational identification can address a…

Astrophysics of Galaxies · Physics 2018-10-10 Tao An , P. Mohan , Sandor Frey

Customized digital backends for Very Long Baseline Interferometry (VLBI) are critical components for radio astronomy observatories. There are several serialized products such as the Digital Baseband Converter (DBBC), Reconfigurable Open…

Instrumentation and Methods for Astrophysics · Physics 2025-02-24 Jiyun Li , Renjie Zhu , Shaoguang Guo , Ping Rui , Zhijun Xu

Aims. We have analysed VLBA 92cm archive data of 44 extragalactic sources in order to identify early targets and potential calibrator sources for the LOFAR radio telescope and the RadioAstron space VLBI mission. Some of these sources will…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 H. Rampadarath , M. A. Garrett , A. Polatidis