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

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...

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Detalles Bibliográficos
Autores: Issaoun, Sara, Johnson, M. D., Blackburn, Lindy, Broderick, Avery E., Tiede, Paul, Wielgus, Maciek, Doeleman, Sheperd S., Falcke, H., Akiyama, K., Bower, G. C., Brinkerink, C. D., Chael, A., Cho, I., Gómez Fernández, José L., Hernández-Gómez, A., Hughes, D., Kino, Motoki, Krichbaum, Thomas P., Liuzzo, Elisabetta, Loinard, Laurent, Markoff, S., Marrone, Daniel P., Mizuno, Y., Morán, J. M., Pidopryhora, Y., Ros, E., Rygl, K., Shen, Zhi-Qiang, Wagner, J.
Tipo de recurso: artículo
Estado:Versión aceptada para publicación
Fecha de publicación:2021
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/256621
Acceso en línea:http://hdl.handle.net/10261/256621
Access Level:acceso abierto
Palabra clave:Black holes
Galaxies: individual: Sgr A*
Galaxy: center
Techniques: interferometric
Descripción
Sumario: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∗. © 2021. The American Astronomical Society. All rights reserved.

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