Millimeter-VLBI

Project

The huge potential of VLBI at submm/mm wavelengths is that it enables the highest resolution imaging currently possible at any wavelength in astronomy. Using ALMA as a phased array to form part of a global VLBI network will offer unprecedented sensitivity at very high angular resolution, making one order of magnitude weaker sources accessible to μas-resolution studies and greatly improving image fidelity for the brighter objects. Moreover, it will allow the shadow of a black hole, a test of general relativity near black holes, investigate jet launch and collimation from AGN and microquasars, pulsar and magnetar emission processes, the chemical history of the universe and the evolution of fundamental constants across cosmic time, maser science, and astrometry.

Contacts: E. Liuzzo (liuzzo@ira.inaf.it), K. Rygl (kazi@ira.inaf.it), N. Marchili (n.marchili@ira.inaf.it), M. Massardi (massardi@ira.inaf.it)

Status

VLBI inherently requires many telescopes to operate together. Existing activities at 3 mm (the Very Long Baseline Array and the Global Millimeter VLBI Array) and at 1 mm (the Event Horizon Telescope project) have laid the groundwork for future coordinated observations. An international consortium is presently constructing a beamformer for the ALMA that will be available as a facility instrument providing substantial improvements to existing VLBI arrays in Bands 1 and 3 (7 and 3 mm).

Nov 2012: the Alma Phasing Project has successfully passed its preliminary design review;
2015: initial ALMA phasing tests;
2016: first ALMA phasing observations;
2019 April 10th: first image of M87 black hole with EHT (including ALMA);
2021 May 12th: first image of Sgr A* black hole with EHT

Italian ARC contribution

We start to get involved in mm-VLBI with ALMA in 2013, making use of our extensive in-house experience with (radio frequency) VLBI. Since January 2018, we are members of the BlackHoleCam and Event Horizon Telescope Consortium where we are contributing in

Calibration and Error working group developing an innovative CASA pipeline for the data reduction of EHT (and VLBI in general) observations;
Time Domain analysis working group to reveal possible periodicities in the data;

The 2019 April 10th we took part in the EHT press release of the first image of a black hole M87 and the 2021 May 12th we contributed to the EHT press release of the first image of SgrA* organizing national press conferences in Rome.

In the following months, in relation to both events, we were invited to several conferences and tv interviews to present the groundbreaking EHT results which direct confirm for the first time the validity of the general relativity theory in extreme gravitational field and for galaxies with different masses.

Work is now focusing on providing the first movie of a black hole, giving important information on how the material is falling into the central massive black hole.

Related publications

EHT related papers from ADS

White papers

High-Angular-Resolution and High-Sensitivity Science Enabled by Beamformed ALMA, Fish et al. 2013, arXiv:1309.3519.
Future mmVLBI Research with ALMA: A European vision, Tilanus et al. 2014

ESO Upgrade Proposal

Phased ALMA as an Element of the Global Millimetre VLBI Array, August 2013