Issaoun, S.S.IssaounJohnson, M. D.M. D.JohnsonBlackburn, L.L.BlackburnBroderick, A.A.BroderickTiede, P.P.TiedeWielgus, M.M.WielgusDoeleman, S. S.S. S.DoelemanFalcke, H.H.FalckeAkiyama, K.K.AkiyamaBower, G. C.G. C.BowerBrinkerink, C. D.C. D.BrinkerinkChael, A.A.ChaelCho, I.I.ChoGómez, J. L.J. L.GómezHernández-Gómez, A.A.Hernández-GómezHughes, D.D.HughesKino, M.M.KinoKrichbaum, T. P.T. P.KrichbaumLIUZZO, Elisabetta TeodorinaElisabetta TeodorinaLIUZZOLoinard, L.L.LoinardMarkoff, S.S.MarkoffMarrone, D. P.D. P.MarroneMizuno, Y.Y.MizunoMoran, J. M.J. M.MoranPidopryhora, Y.Y.PidopryhoraRos, E.E.RosRYGL, Kazi Lucie JessicaKazi Lucie JessicaRYGLShen, Z. -Q.Z. -Q.ShenWagner, J.J.Wagner2022-03-242022-03-2420210004-637Xhttp://hdl.handle.net/20.500.12386/31829Observations 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*.STAMPAenArticle10.3847/1538-4357/ac00b02-s2.0-85111100841https://iopscience.iop.org/article/10.3847/1538-4357/ac00b0https://api.elsevier.com/content/abstract/scopus_id/851111008412021ApJ...915...99IFIS/05 - ASTRONOMIA E ASTROFISICA