The 1.4 mm Core of Centaurus A: First VLBI Results with the South Pole Telescope

Centaurus A (Cen A) is a bright radio source associated with the nearby galaxy NGC 5128 where high-resolution radio observations can probe the jet at scales of less than a light day. The South Pole Telescope (SPT) and the Atacama Pathfinder Experiment performed a single-baseline very-long-baseline interferometry (VLBI) observation of Cen A in 2015 January as part of VLBI receiver deployment for the SPT. We measure the correlated flux density of Cen A at a wavelength of 1.4 mm on a similar to 7000 km (5 G lambda) baseline. Ascribing this correlated flux density to the core, and with the use of a contemporaneous short-baseline flux density from a Submillimeter Array observation, we infer a core brightness temperature of 1.4 x 10(11) K. This is close to the equipartition brightness temperature, where the magnetic and relativistic particle energy densities are equal. Under the assumption of a circular Gaussian core component, we derive an upper limit to the core size phi = 34.0 +/- 1.8 mu as, corresponding to 120 Schwarzschild radii for a black hole mass of 5.5 x. 10(7) M-circle dot.NSF [AST-1207752, AST-1440254, AST-1207704, AST-1310896, AST-1207730, AST-1402161]; ERC Synergy Grant "BlackHoleCam: Imaging the Event Horizon of Black Holes" [610058]; MINECO [AYA-2012-38491-C02-01, AYA2015-63939-C2-2-P]; Generalitat Valenciana [PROMETEOII/2014/057]; National Science Foundation [PLR-1248097]; NSF Physics Frontier Center grant to the Kavli Institute of Cosmological Physics at the University of Chicago [PHY-0114422]; Kavli Foundation; Gordon and Betty Moore Foundation through Grant GBMF [947]; Smithsonian Institution; Academia SinicaThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu