Persistent Non-Gaussian Structure in the Image of Sagittarius A* at 86 GHz
Journal
Date Issued
2021
Author(s)
Issaoun, S.
•
Johnson, M. D.
•
Blackburn, L.
•
Broderick, A.
•
Tiede, P.
•
Wielgus, M.
•
Doeleman, S. S.
•
Falcke, H.
•
Akiyama, K.
•
Bower, G. C.
•
Brinkerink, C. D.
•
Chael, A.
•
Cho, I.
•
Gómez, J. L.
•
Hernández-Gómez, A.
•
Hughes, D.
•
Kino, M.
•
Krichbaum, T. P.
•
•
Loinard, L.
•
Markoff, S.
•
Marrone, D. P.
•
Mizuno, Y.
•
Moran, J. M.
•
Pidopryhora, Y.
•
Ros, E.
•
•
Shen, Z. -Q.
•
Wagner, J.
Abstract
Observations of the Galactic Center supermassive black hole Sagittarius A* (Sgr A*) with very long-baseline interferometry (VLBI) are affected by interstellar scattering along our line of sight. At long radio observing wavelengths (≲1 cm), the scattering heavily dominates image morphology. At 3.5 mm (86 GHz), the intrinsic source structure is no longer sub-dominant to scattering, and thus the intrinsic emission from Sgr A* is resolvable with the Global Millimeter VLBI Array (GMVA). Long-baseline detections to the phased Atacama Large Millimeter/submillimeter Array (ALMA) in 2017 provided new constraints on the intrinsic and scattering properties of Sgr A*, but the stochastic nature of the scattering Requires multiple observing epochs to reliably estimate its statistical properties. We present new observations with the GMVA+ALMA, taken in 2018, which confirm non-Gaussian structure in the scattered image seen in 2017. In particular, the ALMA-GBT baseline shows more flux density than expected for an anistropic Gaussian model, providing a tight constraint on the source size and an upper limit on the dissipation scale of interstellar turbulence. We find an intrinsic source extent along the minor axis of ~100 μas both via extrapolation of longer wavelength scattering constraints and direct modeling of the 3.5 mm observations. Simultaneously fitting for the scattering parameters, we find an at-most modestly asymmetrical (major-to-minor axis ratio of 1.5 ± 0.2) intrinsic source morphology for Sgr A*.
Volume
915
Issue
2
Start page
99
Issn Identifier
0004-637X
Ads BibCode
2021ApJ...915...99I
Rights
open.access
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