Global mm-VLBI array
The Global mm-VLBI Array (Global Millimeter VLBI Array, GMVA) is a worldwide network of radio telescopes to examine radio sources using Very Long Baseline Interferometry (VLBI) in the wavelength range of 3 millimeters (86 GHz). It has been operating since 2002 as the successor to the Coordinated Millimeter VLBI Array and enables regular observations in this wavelength range. Projects are only included in the observation plan according to criteria of the best science (scientific merit). The GMVA is therefore openly accessible to all observers (Open Sky Policy).
The GMVA is coordinated by the Max Planck Institute for Radio Astronomy in Bonn, which also correlates all data recorded on the telescopes. The assessment of the proposed projects is carried out by the participating observatories. Individual observatories reserve the right not to observe individual projects. This is particularly true of the IRAM telescopes and ALMA. The following telescopes regularly take part in the two observation campaigns per year:
- the IRAM telescope (30 m telescope on the Pico del Veleta , Plateau de Bure - currently (2019) only one telescope)
- the 100 m radio telescope Effelsberg of the MPI
- the 20 m telescope in Onsala in Sweden and the 14 m telescope in Metsähovi, Finland
- the 40 m telescope of the OAN (Observatorio Astronómico Nacional) in Yebes
- eight telescopes of the American Very Long Baseline Array (VLBA), which also operates independently at 3 mm wavelength
- the Green Bank Observatory (GBT), which, like the VLBA, will be operated by the NRAO
- the three telescopes of the Korean KVN
- the Atacama Large Millimeter / submillimeter Array (ALMA) has been monitoring specially selected projects with the GMVA about once a year since 2017.
- the Greenland Telescope (GLT) took part in observations on a test basis.
Projects are also accepted which, in addition to the observations at 3 mm, also require observations at 7 mm wavelength in the observation breaks with the antennas of the VLBA. These 7 mm observations are also supported by the 32 m radio telescope near Noto / Sicily.
A similar project, which operates at even shorter wavelengths (1.3 mm), is the Event Horizon Telescope (EHT) for observing black holes . However, the EHT 2019 was operating at the time of observation of a supermassive black hole in M87 is not on a regular basis, d. H. not yet open to all observers.
Typical resolutions of 50 to 70 micro-arcseconds allow the observation of active galactic nuclei ( accretion disks , jets , black holes, etc.), which are often hidden behind clouds of gas and dust.
With the GMVA a survey of ultra-compact extragalactic radio sources (active galactic nuclei, quasars , blazars ) was carried out in 2010/11 . The IRAM telescopes, Effelsberg, Onsala, Metsähovi, Yebes and eight VLBA telescopes were involved.
The GMVA was also used to observe the supermassive black hole Sagittarius A * in the center of the Milky Way. ALMA was also involved.
Web links
Individual evidence
- ↑ MPIfR, VLBI Research
- ↑ Global millimeter VLBI array survey of ultracompact extragalactic radio sources at 86 GHz , MPI Radioastronomie
- ↑ D. Nair, Thomas Krichbaum, Anton Zensus a . a .: Global millimeter VLBI array survey of ultracompact extragalactic radio sources at 86 GHz, Astronomy & Astrophysics, Volume 622, 2019, A92, Arxiv
- ↑ S. Issaoun, A. Zensus, H. Falcke, T. Krichbaum et al., The Size, Shape, and Scattering of Sagittarius A * at 86 GHz: First VLBI with ALMA , Astroph. J. 2019