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, Onsala Space Observatory, Observation Support

Other publications Research

David Macmahon

University of California

Daniel P. Marrone

University of Arizona

Ivan Marti-Vidal

Chalmers, Space, Earth and Environment, Onsala Space Observatory, Onsala Space Observatory, Observation Support

Other publications Research

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 60

Subject Categories

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology

Other Physics Topics

DOI

10.3847/1538-4357/aabe2e

Publication data connected to DOI

More information

Latest update

6/19/2018

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