HIGH-ANGULAR-RESOLUTION AND HIGH-SENSITIVITY SCIENCE ENABLED BY BEAMFORMED ALMA

An international consortium is presently constructing a beamformer for the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile that will be available as a facility instrument. The beamformer will aggregate the entire collecting area of the array into a single, very large aperture. The extraordinary sensitivity of phased ALMA, combined with the extremely fine angular resolution available on baselines to the Northern Hemisphere, will enable transformational new very long baseline interferometry (VLBI) observations in Bands 6 and 7 (1.3 and 0.8 mm) and provide substantial improvements to existing VLBI arrays in Bands 1 and 3 (7 and 3 mm). The ALMA beamformer will have impact on a variety of scientific topics, including accretion and outflow processes around black holes in active galactic nuclei (AGN), tests of general relativity near black holes, 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. 1. PREAMBLE The science case for the ALMA beamformer reflects the broad scientific goals of the VLBI community. Astronomers were solicited for input at a variety of meetings including the 10th European VLBI Network (EVN) Symposium (Manchester 2010), the XXX URSI General Assembly (Istanbul 2011), Bringing Black Holes Into Focus: The Event Horizon Telescope (Tucson 2012), Outflows, Winds and Jets: From Young Stars to Supermassive Black Holes (Charlottesville 2012), From Stars to Black Holes: mm-VLBI with ALMA and Other Telescopes (Garching 2012), and the 11th EVN Symposium (Bordeaux 2012). This document includes input from scientists in all ALMA regions and is designed to be a living document, envisaged to evolve as new science areas are developed and existing areas refined by the community. The case for science with beamformed ALMA is broad, ranging from Galactic to extragalactic science and touching on questions of vital importance for fundamental physics.