Testing the no-hair theorem with event horizon telescope observations of Sagittarius A*

Journal Article · Thu Mar 20 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/784/1/7· OSTI ID:22351533

Broderick, Avery E.; Johannsen, Tim ^[1]; Loeb, Abraham ^[2]; Psaltis, Dimitrios ^[3]

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1. Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, ON N2L 2Y5 (Canada)
2. Institute for Theory and Computation, Harvard University, Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
3. Astronomy and Physics Departments, University of Arizona, 933 North Cherry Street, Tucson, AZ 85721 (United States)

The advent of the Event Horizon Telescope (EHT), a millimeter-wave very long baseline interferometric array, has enabled spatially resolved studies of the subhorizon-scale structure for a handful of supermassive black holes. Among these, the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), presents the largest angular cross section. Thus far, these studies have focused on measurements of the black hole spin and the validation of low-luminosity accretion models. However, a critical input in the analysis of EHT data is the structure of the black hole spacetime, and thus these observations provide the novel opportunity to test the applicability of the Kerr metric to astrophysical black holes. Here we present the first simulated images of a radiatively inefficient accretion flow (RIAF) around Sgr A* employing a quasi-Kerr metric that contains an independent quadrupole moment in addition to the mass and spin that fully characterize a black hole in general relativity. We show that these images can be significantly different from the images of an RIAF around a Kerr black hole with the same spin and demonstrate the feasibility of testing the no-hair theorem by constraining the quadrupolar deviation from the Kerr metric with existing EHT data. Equally important, we find that the disk inclination and spin orientation angles are robust to the inclusion of additional parameters, providing confidence in previous estimations assuming the Kerr metric based on EHT observations. However, at present, the limits on potential modifications of the Kerr metric remain weak.

• OSTI ID: 22351533
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 784; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
ASTROPHYSICS
BLACK HOLES
CROSS SECTIONS
GENERAL RELATIVITY THEORY
GRAVITATION
IMAGES
INCLINATION
INCLUSIONS
KERR METRIC
LUMINOSITY
MASS
MILKY WAY
MODIFICATIONS
QUADRUPOLE MOMENTS
SIMULATION
SPACE-TIME
SPIN
TELESCOPES
VALIDATION