An ALMA beamformer for ultra-high resolution VLBI and phased array science

Alef, W.; Anderson, J. M.; Rottmann, Helge; Roy, A. L.; Crew, G.; Doeleman, S.; Hecht, M. H.; Ruszczyk, Chester A.; Fish, Vincent L.; Lonsdale, Colin J.; Hiriart, R.; Greenberg, Joe; Lacasse, Rich; Shillue, Bill; Amestica, Rodrigo; Honma, Mareki; Pradel, Nicolas; Inoue, Makoto; Nagar, Neil M.; Saez, Alejandro

doi:10.22323/1.178.0053

Cited by 5 publications

(5 citation statements)

References 6 publications

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“…Since at mm-wavelengths weather is a limiting factor, triggered VLBI observations in pre-allocated longer time blocks are very feasible and require only moderate logistical efforts at the individual stations. The addition of the phased ALMA, equivalent to a ∼ 85 m dish, to the existing VLBI arrays (at ν ≥ 43 GHz) will lower the detection limits for mm-VLBI by up to 2 orders of magnitude (see [1] for the ALMA Phasing Project (APP)). Global mm-VLBI with ALMA however will be only possible, if in parallel to the ongoing technical development also a strong scientific user community not only obtains interesting results using the existing mm-VLBI arrays, but also actively pushes ALMA to this new frontier.…”

Section: Future Perspectivementioning

confidence: 99%

Zooming towards the Event Horizon - mm-VLBI today and tomorrow

Krichbaum¹,

Roy²,

Wagner³

et al. 2016

Proceedings of 11th European VLBI Network Symposium &Amp; Users Meeting — PoS(11th EVN Symposium)

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Global VLBI imaging at millimeter and sub-millimeter wavelength overcomes the opacity barrier of synchrotron self-absorption in AGN and opens the direct view into sub-pc scale regions not accessible before. Since AGN variability is more pronounced at short millimeter wavelength, mm-VLBI can reveal structural changes in very early stages after outbursts. When combined with observations at longer wavelength, global 3 mm and 1 mm VLBI adds very detailed information on the source structure. This helps to determine fundamental physical properties at the jet base, and in the vicinity of super-massive black holes at the center of AGN. Here we present new results from multi-frequency mm-VLBI imaging of OJ 287 during a major outburst. We also report on a successful 1.3 mm VLBI experiment with the APEX telescope in Chile. This observation sets a new world record in angular resolution. It also opens the path towards future mm-VLBI with ALMA, which aims at the mapping of the black hole event horizon in nearby galaxies, and the study of the roots of jets in AGN.

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Section: Future Perspectivementioning

confidence: 99%

Zooming towards the Event Horizon - mm-VLBI today and tomorrow

Krichbaum¹,

Roy²,

Wagner³

et al. 2016

Proceedings of 11th European VLBI Network Symposium &Amp; Users Meeting — PoS(11th EVN Symposium)

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“…Several upgrades to improve the sensitivity of the array are underway. Most importantly, a multinational team is developing a phased array processor for the Atacama Large Millimeter/sub-Millimeter Array (ALMA) that will turn it into an extremely sensitive aperture for inclusion in VLBI arrays [10,11,12]. US EHT sites are upgrading their signal chains to match ALMA's bandwidth.…”

Section: Status Of the Ehtmentioning

confidence: 99%

New results from the Event Horizon Telescope

Fish¹

2016

Proceedings of 11th European VLBI Network Symposium &Amp; Users Meeting — PoS(11th EVN Symposium)

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The Event Horizon Telescope is a project to observe and eventually image the Schwarzschild radius-scale structure around nearby supermassive black holes using 1.3 mm VLBI. Observations in recent years have made use of telescopes in Hawaii, Arizona, and California, with telescopes in Chile and Europe likely to participate in future observing sessions as well. Sensitivity upgradesincluding an ongoing project to phase up the ALMA array-and increased baseline coverage will soon make imaging a reality. In the meantime, non-imaging observations have been successful in producing scientific results. This contribution reports on three recent results: the detection of Schwarzschild radius-structure in the 1.3 mm emission from the black hole in the center of M87, which strongly supports the existence of an accretion disk rotating in a prograde sense around a rotating black hole; the detection of nonzero closure phases in AGN sources such as 1924−292, which allow their submilliarcsecond structure to be modelled; and the detection of cross-polarized fringes, which hints at complicated linear polarization structure in at least one source.

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“…To combine two independent signals coherently, interferometry between two antennas of the array is first carried out with a radio continuum source such as a quasar to determine the delay among the antennas. Then, the delay, delay rate, and phase information are obtained from all combinations of each antenna pair by the least-squares method (Alef et al 2012) or the minimum spanning tree algorithm (Takeuchi et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Development of the Phase-up Technology of the Radio Telescopes: 6.7 GHz Methanol Maser Observations with Phased Hitachi 32 m and Takahagi 32 m Radio Telescopes

Takefuji

Sugiyama

Yonekura

et al. 2017

PASP

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For the sake of high-sensitivity 6.7 GHz methanol maser observations, we developed a new technology for coherently combining the two signals from the Hitachi 32 m radio telescope and the Takahagi 32 m radio telescope of the Japanese Very long baseline interferometer Network (JVN), where the two telescopes were separated by about 260 m. After the two telescopes were phased as a twofold larger single telescope, the mean signal-to-noise ratio (SNR) of the 6.7 GHz methanol masers observed by the phased telescopes was improved to 1.254-fold higher than that of the single dish, through a Very Long Baseline Interferometry (VLBI) experiment on the 50 km baseline of the Kashima 34 m telescope and the 1000 km baseline of the Yamaguchi 32 m telescope. Furthermore, we compared the SNRs of the 6.7 GHz maser spectra for two methods. One is a VLBI method and the other is the newly developed digital position switching, which is a similar technology to that used in noise-cancelling headphones. Finally, we confirmed that the mean SNR of method of the digital position switching (ON-OFF) was 1.597-fold higher than that of the VLBI method.

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An ALMA beamformer for ultra-high resolution VLBI and phased array science

Cited by 5 publications

References 6 publications

Zooming towards the Event Horizon - mm-VLBI today and tomorrow

Zooming towards the Event Horizon - mm-VLBI today and tomorrow

New results from the Event Horizon Telescope

Development of the Phase-up Technology of the Radio Telescopes: 6.7 GHz Methanol Maser Observations with Phased Hitachi 32 m and Takahagi 32 m Radio Telescopes

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