Persistent Non-Gaussian Structure in the Image of Sagittarius A* at 86 GHz

DOI: 
10.3847/1538-4357/ac00b0
Publication date: 
24/07/2021
Main author: 
Issaoun, S.
IAA authors: 
Gómez, J. L.
Authors: 
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.;Liuzzo, E.;Loinard, L.;Markoff, S.;Marrone, D. P.;Mizuno, Y.;Moran, J. M.;Pidopryhora, Y.;Ros, E.;Rygl, K.;Shen, Z. -Q.;Wagner, J.
Journal: 
The Astrophysical Journal
Publication type: 
Article
Volume: 
915
Pages: 
99
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*.
Database: 
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2021ApJ...915...99I/abstract
ADS Bibcode: 
2021ApJ...915...99I
Keywords: 
Black holes;Galactic center;Very long baseline interferometry;Radio interferometry;Interstellar medium;162;565;1769;1346;847;Astrophysics - Astrophysics of Galaxies;Astrophysics - High Energy Astrophysical Phenomena