The Size, Shape, and Scattering of Sagittarius A∗ at 86 GHz: First VLBI with ALMA
Artikel i vetenskaplig tidskrift, 2019

The Galactic center supermassive black hole Sagittarius A∗ (Sgr A∗) is one of the most promising targets to study the dynamics of black hole accretion and outflow via direct imaging with very long baseline interferometry (VLBI). At 3.5 mm (86 GHz), the emission from Sgr A∗ is resolvable with the Global Millimeter VLBI Array (GMVA). We present the first observations of Sgr A∗ with the phased Atacama Large Millimeter/submillimeter Array (ALMA) joining the GMVA. Our observations achieve an angular resolution of ∼87 μas, improving upon previous experiments by a factor of two. We reconstruct a first image of the unscattered source structure of Sgr A∗ at 3.5 mm, mitigating the effects of interstellar scattering. The unscattered source has a major-axis size of 120 ±34 μas (12 ±3.4 Schwarzschild radii) and a symmetrical morphology (axial ratio of ), which is further supported by closure phases consistent with zero within 3σ. We show that multiple disk-dominated models of Sgr A∗ match our observational constraints, while the two jet-dominated models considered are constrained to small viewing angles. Our long-baseline detections to ALMA also provide new constraints on the scattering of Sgr A∗, and we show that refractive scattering effects are likely to be weak for images of Sgr A∗ at 1.3 mm with the Event Horizon Telescope. Our results provide the most stringent constraints to date for the intrinsic morphology and refractive scattering of Sgr A∗, demonstrating the exceptional contribution of ALMA to millimeter VLBI.

galaxies: individual (Sgr A∗)

Galaxy: center

accretion, accretion disks

techniques: interferometric

Författare

S. Issaoun

Harvard-Smithsonian Center for Astrophysics

Radboud Universiteit

Michael D. Johnson

Harvard-Smithsonian Center for Astrophysics

Lindy Blackburn

Harvard-Smithsonian Center for Astrophysics

C. D. Brinkerink

Radboud Universiteit

M. Mościbrodzka

Radboud Universiteit

A. Chael

Harvard-Smithsonian Center for Astrophysics

C. Goddi

Radboud Universiteit

Universiteit Leiden

Ivan Marti-Vidal

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

Jan Wagner

Max Planck-institutet

S. Doeleman

Harvard-Smithsonian Center for Astrophysics

H.D. Falcke

Radboud Universiteit

T.P. Krichbaum

Max Planck-institutet

Kazunori Akiyama

National Radio Astronomy Observatory

Massachusetts Institute of Technology (MIT)

U. Bach

Max Planck-institutet

K. L. Bouman

Harvard-Smithsonian Center for Astrophysics

G. C. Bower

Academia Sinica

Avery E. Broderick

Perimeter Institute for Theoretical Physics

I. Cho

University of Science and Technology (UST)

Korea Astronomy and Space Science Institute

G. Crew

Massachusetts Institute of Technology (MIT)

Jason Dexter

Max Planck-institutet

V. Fish

Massachusetts Institute of Technology (MIT)

R. Gold

Perimeter Institute for Theoretical Physics

Johann Wolfgang Goethe Universität Frankfurt am Main

J. L. Gomez

CSIC - Instituto de Astrofísica de Andalucía (IAA)

K. Hada

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

A. Hernández-Gómez

Université de Toulouse

Universidad Nacional Autonoma de Mexico

M. Janßen

Radboud Universiteit

M. Kino

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

M. Kramer

Max Planck-institutet

L. Loinard

Universidad Nacional Autonoma de Mexico

R.S. Lu

Shanghai Astronomical Observatory

Max Planck-institutet

S. Markoff

Universiteit Van Amsterdam

D. P. Marrone

University of Arizona

L. D. Matthews

Massachusetts Institute of Technology (MIT)

J. M. Moran

Harvard-Smithsonian Center for Astrophysics

C. Müller

Radboud Universiteit

Max Planck-institutet

F. Roelofs

Radboud Universiteit

Eduardo Ros

Max Planck-institutet

H. Rottmann

Max Planck-institutet

S. Sanchez

Instituto de Radioastronomia Milimetrica

R. P. J. Tilanus

Radboud Universiteit

Universiteit Leiden

P. Vicente

Observatorio de Yebes (IGN)

M. Wielgus

Harvard-Smithsonian Center for Astrophysics

A.J. Zensus

Max Planck-institutet

G. Y. Zhao

Korea Astronomy and Space Science Institute

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 871 1 30

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.3847/1538-4357/aaf732

Mer information

Senast uppdaterat

2019-03-05