Publications

2020
J. Y. Kim et al. 2020. “Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution.” Astronomy and Astrophysics, 640, A69, Pp. 21. Publisher's VersionAbstract

3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique - global Very Long Baseline Interferometry (VLBI) at 1.3 mm (230 GHz) - to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable γ-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array (ALMA), at an angular resolution of ∼20 μas (at a redshift of z = 0.536 this corresponds to ∼0.13 pc ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M☉). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation. We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across different imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI "core". This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet. We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1.3 and ∼1.7 μas day-1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3 mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≲1010 K, a magnitude or more lower than typical values seen at ≥7 mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.

 

The data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/640/A69 and at http://https://eventhorizontelescope.org/for-astronomers/data
A. Broderick et al. 2020. “THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope.” The Astrophysical Journal, 897, 2, Pp. id. 139. Publisher's Version
R. Gold et al. 2020. “Verification of Radiative Transfer Schemes for the EHT.” The Astrophysical Journal, 897, 2, Pp. id. 148. Publisher's Version
2019
C. Goddi et al. 2019. “First M87 Event Horizon Telescope Results and the Role of ALMA,” 177, Pp. 25-35. Publisher's Version
L. Christensen et al. 2019. “An Unprecedented Global Communications Campaign for the Event Horizon Telescope First Black Hole Image.” CAPJ, 26, 11. Publisher's Version
C. Goddi et al. 2019. “Calibration of ALMA as a phased array: ALMA observations during the 2017 VLBI campaign.” PASP, 131, 1001, Pp. 075003. Publisher's Version
L. Blackburn et al. 2019. “EHT-HOPS pipeline for millimeter VLBI data reduction.” ApJ, 882, 23. Publisher's Version
O. Porth et al. 2019. “The Event Horizon General Relativistic Magnetohydrodynamic Code Comparison Project.” ApJS, 243, 26. Publisher's Version
The EHT Collaboration et al. 2019. “First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole.” ApJL, 875, Pp. 1. Publisher's Version
The EHT Collaboration et al. 2019. “First M87 Event Horizon Telescope Results. II. Array and Instrumentation.” ApJL, 875, Pp. 2. Publisher's Version
The EHT Collaboration et al. 2019. “First M87 Event Horizon Telescope Results. III. Data Processing and Calibration.” ApJL, 875, Pp. 3. Publisher's Version
The EHT Collaboration et al. 2019. “First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole.” ApJL, 875, Pp. 4. Publisher's Version
The EHT Collaboration et al. 2019. “First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring.” ApJL, 875, Pp. 5. Publisher's Version
The EHT Collaboration et al. 2019. “First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole.” ApJL, 875, Pp. 6. Publisher's Version
M. Janssen et al. 2019. “rPICARD: A CASA-based Calibration Pipeline for VLBI Data. Calibration and imaging of 7 mm VLBA observations of the AGN jet in M87.” A&A, 626, 75. Publisher's Version
F. Roelofs et al. 2019. “Simulations of imaging the event horizon of Sagittarius A* from space.” A&A, 625, 124. Publisher's Version
S. Issaoun et al. 2019. “The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA.” ApJ, 871, 1, Pp. 30. Publisher's Version
Z. Zhu et al. 2019. “Testing General Relativity with the Black Hole Shadow Size and Asymmetry of Sagittarius A*: Limitations from Interstellar Scattering.” ApJ, 870, 1, Pp. 6. Publisher's Version
2018
G. C. Bower et al. 2018. “ALMA Polarimetry of Sgr A*: Probing the Accretion Flow from the Event Horizon to the Bondi Radius.” ApJ, 868, 2, Pp. 101. Publisher's Version
L. Medeiros, C.-K. Chan, F. Özel, D. Psaltis, J. Kim, D. P. Marrone, and A. Sadowski. 2018. “GRMHD Simulations of Visibility Amplitude Variability for Event Horizon Telescope Images of Sgr A*.” ApJ, 856, 2, Pp. 13.

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