Detection of Intrinsic Source Structure at similar to 3 Schwarzschild Radii with Millimeter-VLBI Observations of SAGITTARIUS A*
Journal article, 2018
We report results from very long baseline interferometric (VLBI) observations of the supermassive black hole in the Galactic center, Sgr A*, at 1.3 mm (230 GHz). The observations were performed in 2013 March using six VLBI stations in Hawaii, California, Arizona, and Chile. Compared to earlier observations, the addition of the APEX telescope in Chile almost doubles the longest baseline length in the array, provides additional uv coverage in the N-S direction, and leads to a spatial resolution of similar to 30 mu as (similar to 3 Schwarzschild radii) for Sgr A*. The source is detected even at the longest baselines with visibility amplitudes of similar to 4%-13% of the total flux density. We argue that such flux densities cannot result from interstellar refractive scattering alone, but indicate the presence of compact intrinsic source structure on scales of similar to 3 Schwarzschild radii. The measured nonzero closure phases rule out point-symmetric emission. We discuss our results in the context of simple geometric models that capture the basic characteristics and brightness distributions of disk-and jet-dominated models and show that both can reproduce the observed data. Common to these models are the brightness asymmetry, the orientation, and characteristic sizes, which are comparable to the expected size of the black hole shadow. Future 1.3 mm VLBI observations with an expanded array and better sensitivity will allow more detailed imaging of the horizon-scale structure and bear the potential for a deep insight into the physical processes at the black hole boundary.
Galaxy: center
techniques: interferometric
techniques: high angular resolution
submillimeter: general
Author
Ru-Sen Lu
Max Planck Society
Massachusetts Institute of Technology (MIT)
Thomas P. Krichbaum
Max Planck Society
Alan L. Roy
Max Planck Society
Vincent L. Fish
Massachusetts Institute of Technology (MIT)
Sheperd S. Doeleman
Harvard-Smithsonian Center for Astrophysics
Massachusetts Institute of Technology (MIT)
Michael D. Johnson
Harvard-Smithsonian Center for Astrophysics
Kazunori Akiyama
National Astronomical Observatory of Japan
University of Tokyo
Massachusetts Institute of Technology (MIT)
Dimitrios Psaltis
University of Arizona
Walter Alef
Max Planck Society
Keiichi Asada
Academia Sinica
Christopher Beaudoin
Massachusetts Institute of Technology (MIT)
Alessandra Bertarini
University of Bonn
Max Planck Society
Lindy Blackburn
Harvard-Smithsonian Center for Astrophysics
Ray Blundell
Harvard-Smithsonian Center for Astrophysics
Geoffrey C. Bower
Academia Sinica
Christiaan Brinkerink
Radboud University
Avery E. Broderick
University of Waterloo
Perimeter Institute for Theoretical Physics
Roger Cappallo
Massachusetts Institute of Technology (MIT)
Geoffrey B. Crew
Massachusetts Institute of Technology (MIT)
Jason Dexter
Max Planck Society
Matt Dexter
University of California
Heino Falcke
Radboud University
Max Planck Society
Netherlands Institute for Radio Astronomy (ASTRON)
Robert Freund
University of Arizona
Per Friberg
East Asian Observatory
Christopher H. Greer
University of Arizona
Mark A. Gurwell
Harvard-Smithsonian Center for Astrophysics
Paul T. P. Ho
Academia Sinica
Mareki Honma
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
Makoto Inoue
Academia Sinica
Junhan Kim
University of Arizona
James Lamb
California Institute of Technology (Caltech)
Michael Lindqvist
Chalmers, Space, Earth and Environment, Onsala Space Observatory
David Macmahon
University of California
Daniel P. Marrone
University of Arizona
Ivan Marti-Vidal
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Karl M. Menten
Max Planck Society
James M. Moran
Harvard-Smithsonian Center for Astrophysics
Neil M. Nagar
University of Concepcion
Richard L. Plambeck
University of California
Rurik A. Primiani
Harvard-Smithsonian Center for Astrophysics
Alan E. E. Rogers
Massachusetts Institute of Technology (MIT)
Eduardo Ros
Max Planck Society
Universitat de Valencia
Helge Rottmann
Max Planck Society
Jason SooHoo
Massachusetts Institute of Technology (MIT)
Justin Spilker
The University of Texas at Austin
University of Arizona
Jordan Stone
University of Arizona
Peter Strittmatter
University of Arizona
Remo P. J. Tilanus
Radboud University
Leiden University
Michael Titus
Massachusetts Institute of Technology (MIT)
Laura Vertatschitsch
Harvard-Smithsonian Center for Astrophysics
Jan Wagner
Korea Astronomy and Space Science Institute
Max Planck Society
Jonathan Weintroub
Harvard-Smithsonian Center for Astrophysics
Melvyn Wright
University of California
Ken H. Young
Harvard-Smithsonian Center for Astrophysics
J. Anton Zensus
Max Planck Society
Lucy M. Ziurys
University of Arizona
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 859 1 60Subject Categories
Meteorology and Atmospheric Sciences
Astronomy, Astrophysics and Cosmology
Other Physics Topics
DOI
10.3847/1538-4357/aabe2e