scholarly journals VLBI in Australia ? A Review

1991 ◽  
Vol 44 (6) ◽  
pp. 785 ◽  
Author(s):  
DL Jauncey
Keyword(s):  
High Resolution ◽  
Very Long Baseline Interferometry ◽  
Research Field ◽  
Asia Pacific ◽  
Vital Function ◽  
Future Developments ◽  
Long Baseline ◽  
The Status ◽  
Formal Basis ◽  
Fruitful Research

After two decades of Australian VLBI (very long baseline interferometry), high-resolution radio astronomy continues to be an active and fruitful research field. The status of Australian VLBI programs in astrophysics, astrometry and geodesy is reviewed and likely future developments are outlined. In addition to research programs with the Australian VLBI network, a number of successful collaborative projects are underway with overseas VLBI observatories. The inception of the Asia-Pacific Telescope will provide an important formal basis for fostering and extending international VLBI experiments in the Australian hemisphere. The APT will also serve a vital function in coordinating ground-based observations when the Soviet and Japanese VLBI space missions, Radioastron and VSOP, are launched in the middle of this decade. However, continued viable Australian participation in VLBI into the nineties will require new wide-bandwidth recording systems and an Australian VLBI correlator.

scholarly journals Development of a Radio-Astrometric Catalog by Means of Very Long Baseline Interferometry Observations

1980 ◽  
Vol 56 ◽  
pp. 351-357
Author(s):  
J. L. Fanselow ◽  
O. J. Sovers ◽  
J. B. Thomas ◽  
F. R. Bletzacker ◽  
T. J. Kearns ◽  
...  
Keyword(s):  
Very Long Baseline Interferometry ◽  
Radio Sources ◽  
Radio Interferometry ◽  
Long Baseline ◽  
California Institute Of Technology ◽  
The Status ◽  
Institute Of Technology ◽  
Global Accuracy ◽  
Celestial Sphere ◽  
Interplanetary Navigation

AbstractThe Jet Propulsion Laboratory of the California Institute of Technology has been developing a radio-astrometric catalogue for use in the application of radio interferometry to interplanetary navigation and geodesy. The catalogue consists of approximately 100 compact extragalactic radio sources whose relative positions have formal uncertainties of the order of 0”.01. The sources cover nearly all of the celestial sphere above -40° declination. By using the optical counterparts of many of these radio sources, we have tied this radio reference frame to the FK4 optical system with a global accuracy of approximately 0”.01. This paper describes the status of this work.

scholarly journals Open our eyes to wider fields in VLBI surveys

2016 ◽  
Vol 12 (S324) ◽  
pp. 247-248
Author(s):  
Kristóf Rozgonyi ◽  
Sándor Frey
Keyword(s):  
High Resolution ◽  
Very Long Baseline Interferometry ◽  
Field Of View ◽  
Practical Reasons ◽  
Radio Sources ◽  
Long Baseline ◽  
Extended Radio ◽  
Automated Process ◽  
Computationally Intensive ◽  
New Phenomena

AbstractThe observation and imaging of hundreds or thousands of radio sources with the technique of very long baseline interferometry (VLBI) is a computationally intensive task. However, these surveys allow us to conduct statistical investigations of large source samples, and also to discover new phenomena or types of objects. The field of view of these high-resolution VLBI imaging observations is typically a few arcseconds at cm wavelengths. For practical reasons, often a much smaller fraction of the field, the central region is imaged only. With an automated process we imaged the ~1.5-arcsec radius fields around more than 1000 radio sources, and found a variety of extended radio structures. Some of them are yet unknown in the literature.

scholarly journals Very long baseline interferometry observation of the triple AGN candidate J0849+1114

2019 ◽  
Vol 630 ◽  
pp. L5 ◽  
Author(s):  
K. É. Gabányi ◽  
S. Frey ◽  
S. Satyapal ◽  
A. Constantin ◽  
R. W. Pfeifle
Keyword(s):  
High Resolution ◽  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Very Long Baseline Interferometry ◽  
Galactic Nuclei ◽  
Long Baseline ◽  
Continuum Observation ◽  
The Hierarchical Structure ◽  
Multi Wavelength ◽  
Interferometric Observation

Context. In the hierarchical structure formation model, galaxies grow through various merging events. Numerical simulations indicate that mergers can enhance the activity of central supermassive black holes in galaxies. Aims. A system of three interacting galaxies, called J0849+1114, has recently been identified and multi-wavelength evidence of all three galaxies containing active galactic nuclei has recently been found. The system has substantial radio emission; we aim to investigate the origin of this radio emission with a high-resolution radio interferometric observation and to discover whether it is related to star formation or to one or more of the active galactic nuclei in the system. Methods. We performed high-resolution continuum observation of J0849+1114 with the European Very Long Baseline Interferometry Network at 1.7 GHz. Results. We detected one compact radio emitting source at the position of the easternmost nucleus. Its high brightness temperature and radio power indicate that the radio emission originates from a radio-emitting active galactic nucleus. Additionally, we found that significant amount of flux density is contained in ∼100 milliarcsec-scale feature related to the active nucleus.

scholarly journals High-resolution radio astronomy: An outlook for Africa

2019 ◽  
Vol 15 (S356) ◽  
pp. 137-142
Author(s):  
Leonid I. Gurvits ◽  
Robert Beswick ◽  
Melvin Hoare ◽  
Ann Njeri ◽  
Jay Blanchard ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Structural Changes ◽  
Very Long Baseline Interferometry ◽  
Galactic Nuclei ◽  
High Sensitivity ◽  
Radio Sources ◽  
Long Baseline ◽  
The World ◽  
The Status ◽  
Near Term

AbstractVery Long Baseline Interferometry (VLBI) offers unrivalled resolution in studies of celestial radio sources. The subjects of interest of the current IAU Symposium, the Active Galactic Nuclei (AGN) of all types, constitute the major observing sample of modern VLBI networks. At present, the largest in the world in terms of the number of telescopes and geographical coverage is the European VLBI Network (EVN), which operates under the “open sky” policy via peer-reviewed observing proposals. Recent EVN observations cover a broad range of science themes from high-sensitivity monitoring of structural changes in inner AGN areas to observations of tidal eruptions in AGN cores and investigation of redshift-dependent properties of parsec-scale radio structures of AGN. All the topics above should be considered as potentially rewarding scientific activities of the prospective African VLBI Network (AVN), a natural “scientific ally” of EVN. This contribution briefly describe the status and near-term strategy for the AVN development as a southern extension of the EVN-AVN alliance and as an eventual bridge to the Square Kilometre Array (SKA) with its mid-frequency core in South Africa.

Masers as probes of the gas dynamics close to forming high-mass stars

2017 ◽  
Vol 13 (S336) ◽  
pp. 201-206 ◽  
Author(s):  
Luca Moscadelli ◽  
Alberto Sanna ◽  
Ciriaco Goddi
Keyword(s):  
Gas Dynamics ◽  
Very Long Baseline Interferometry ◽  
High Mass ◽  
Powerful Technique ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Massive Forming ◽  
Typical Distances ◽  
New Generation ◽  
Better Than

AbstractImaging the inner few 1000 AU around massive forming stars, at typical distances of several kpc, requires angular resolutions of better than 0″.1. Very Long Baseline Interferometry (VLBI) observations of interstellar molecular masers probe scales as small as a few AU, whereas (new-generation) centimeter and millimeter interferometers allow us to map scales of the order of a few 100 AU. Combining these informations all together, it presently provides the most powerful technique to trace the complex gas motions in the proto-stellar environment. In this work, we review a few compelling examples of this technique and summarize our findings.

scholarly journals A Tri-Band Cooled Receiver for Geodetic VLBI

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2662
Author(s):  
José A. López-Pérez ◽  
Félix Tercero-Martínez ◽  
José M. Serna-Puente ◽  
Beatriz Vaquero-Jiménez ◽  
María Patino-Esteban ◽  
...  
Keyword(s):  
Very Long Baseline Interferometry ◽  
Low Noise ◽  
Cryogenic Temperatures ◽  
Geospatial Information ◽  
Receiver Noise ◽  
Geodetic Vlbi ◽  
Long Baseline ◽  
Front End ◽  
X Band ◽  
Santa Maria

This paper shows a simultaneous tri-band (S: 2.2–2.7 GHz, X: 7.5–9 GHz and Ka: 28–33 GHz) low-noise cryogenic receiver for geodetic Very Long Baseline Interferometry (geo-VLBI) which has been developed at Yebes Observatory laboratories in Spain. A special feature is that the whole receiver front-end is fully coolable down to cryogenic temperatures to minimize receiver noise. It was installed in the first radio telescope of the Red Atlántica de Estaciones Geodinámicas y Espaciales (RAEGE) project, which is located in Yebes Observatory, in the frame of the VLBI Global Observing System (VGOS). After this, the receiver was borrowed by the Norwegian Mapping Autorithy (NMA) for the commissioning of two VGOS radiotelescopes in Svalbard (Norway). A second identical receiver was built for the Ishioka VGOS station of the Geospatial Information Authority (GSI) of Japan, and a third one for the second RAEGE VGOS station, located in Santa María (Açores Archipelago, Portugal). The average receiver noise temperatures are 21, 23, and 25 Kelvin and the measured antenna efficiencies are 70%, 75%, and 60% in S-band, X-band, and Ka-band, respectively.

scholarly journals Common Phase and Structure Misidentifications in High-Resolution TEM Characterization of Perovskite Materials

2020 ◽  
Vol 6 (1) ◽  
pp. 1
Author(s):  
Yu-Hao Deng
Keyword(s):  
High Resolution ◽  
Research Field ◽  
Structure Characterization ◽  
Phase Identification ◽  
Lead Iodide ◽  
Perovskite Materials ◽  
High Resolution Tem ◽  
Methylammonium Lead Iodide ◽  
Dose Imaging

High-resolution TEM (HRTEM) is a powerful tool for structure characterization. However, methylammonium lead iodide (MAPbI3) perovskite is highly sensitive to electron beams and easily decomposes into lead iodide (PbI2). Misidentifications, such as PbI2 being incorrectly labeled as perovskite, are widely present in HRTEM characterization and would negatively affect the development of perovskite research field. Here misidentifications in MAPbI3 perovskite are summarized, classified, and corrected based on low-dose imaging and electron diffraction (ED) simulations. Corresponding crystallographic parameters of intrinsic tetragonal MAPbI3 and the confusable hexagonal PbI2 are presented unambiguously. Finally, the method of proper phase identification and some strategies to control the radiation damage in HRTEM are provided. This warning paves the way to avoid future misinterpretations in HRTEM characterization of perovskite and other electron beam-sensitive materials.

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