New results from the Event Horizon Telescope

Abstract

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.

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

“…Recent progress in the development of digital VLBI recording systems has led to larger observing bandwidth (& data rates) and higher sensitivities. The VLBI detection of ultra-compact emission regions in Sgr A* and M 87 at 230 GHz and with telescopes in the USA (SMTO, SMA, CARMA) is another important step towards global mm-/sub-mm VLBI, which aims at the ∼ 10 µas scale imaging of the event horizon in nearby black holes ( [4], Event Horizon Telescope: EHT).…”

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

“…VLBI observations at the highest frequencies of 86 GHz and above have the potential to probe deeper into the cores of active galactic nuclei (e.g. [1] and [2] this conference) where observations of nearby objects, in particular M87 and Sgr A*, could allow investigating the extreme physical conditions down to the central massive black holes in those objects.…”

“…Both the CARMA and SMA [4] arrays have also recently been phased for VLBI observations at 1.3mm wavelength (e.g. [2]).…”