The Intrinsic Two-Dimensional Size of Sagittarius A*

Abstract

We report the detection of the two-dimensional structure of the radio source associated with the Galactic Center black hole, Sagittarius A*, obtained from Very Long Baseline Array (VLBA) observations at a wavelength of 7mm. The intrinsic source is modeled as an elliptical Gaussian with major axis size 35.4 x 12.6 R_S in position angle 95 deg East of North. This morphology can be interpreted in the context of both jet and accretion disk models for the radio emission. There is supporting evidence in large angular-scale multi-wavelength observations for both source models for a preferred axis near 95 deg. We also place a maximum peak-to-peak change of 15% in the intrinsic major axis size over five different epochs. Three observations were triggered by detection of near infrared (NIR) flares and one was simultaneous with a large X-ray flare detected by NuSTAR. The absence of simultaneous and quasi-simultaneous flares indicates that not all high energy events produce variability at radio wavelengths. This supports the conclusion that NIR and X-ray flares are primarily due to electron excitation and not to an enhanced accretion rate onto the black hole.

accepted for publication in ApJ

References in corpus (8)

• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
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• A Magnetohydrodynamic Model for the Formation of Episodic Jets
• How to hide large scale outflows: size constraints on the jets of Sgr A*
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• Jet-lag in Sgr A*: What size and timing measurements tell us about the central black hole in the Milky Way
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• The Power of Imaging: Constraining the Plasma Properties of GRMHD Simulations using EHT Observations of Sgr A*
• The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA
• Simulations of imaging the event horizon of Sagittarius A* from space
• The Surprisingly Small Impact of Magnetic Fields On The Inner Accretion Flow of Sagittarius A* Fueled By Stellar Winds
• Discovery of Substructure in the Scatter-Broadened Image of Sgr A*
• Polarized light from Sgr A* in the near-infrared $K_s$-band
• The intrinsic structure of Sagittarius A* at 1.3 cm and 7 mm
• No asymmetric outflows from Sagittarius A* during the pericenter passage of the gas cloud G2
• Multi-wavelength torus-jet model for Sgr~A*
• A single HII region model of the strong interstellar scattering towards Sgr A*
• Confronting the jet model of Sgr A* with the Faraday rotation measure observations
• Trigonometric parallax and proper motion of Sagittarius A* measured by VERA using the new broad-band back-end system OCTAVE-DAS
• Monitoring the Size and Flux Density of Sgr A* during the Active State in 2019 with East Asian VLBI Network