To obtain robust results, independent of assumptions made during the data calibration, we base our scientific analysis on two datasets, which we obtained from two independent calibration pipelines: rPICARD 9 and EHT-HOPS 10 (‘Data reduction pipelines’ in Methods).įigure 1 presents our reconstruction of the jet image structure derived from the EHT data using a regularized maximum likelihood method, next to the large-scale source morphology and the similarly edge-brightened morphology of the Messier 87 (M87) jet on comparable gravitational scales. The EHT, as a novel and heterogeneous high-frequency very-long-baseline interferometry (VLBI) array, poses unique calibration challenges. We have observed Cen A in a six-hour-long track on 10 April 2017. It has recently become possible to model these scales with sophisticated general relativistic magnetohydrodynamics (GRMHD) simulations 8, where jet ejection and their symbiotic relationship with accretion flows are simulated from first principles. 7), we are probing jet structures down to scales of ~200 gravitational radii r g ≈ 0.6 light days. Here we present the first image of Centaurus A (Cen A) obtained by the Event Horizon Telescope (EHT) with a nominal resolution of 25 microarcseconds (μas) at a wavelength ( λ) of 1.3 mm. This location further supports the universal scale invariance of black holes over a wide range of masses 5, 6. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow 4 should be visible at terahertz frequencies. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 r g scales remarkably well. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. Compared with previous observations 3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. Centaurus A is the closest radio-loud source to Earth 2. Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii ( r g ≡ G M/ c 2) scales in nearby sources 1.
Nature Astronomy volume 5, pages 1017–1028 ( 2021) Cite this article The Event Horizon Telescope Collaboration.Event Horizon Telescope observations of the jet launching and collimation in Centaurus A
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