Fig. 6: The effects of different model choices: magnetic field, rotation direction and orbital velocity.
From: Orbital polarimetric tomography of a flare near the Sagittarius A* supermassive black hole
Top: validation-χ2 under each model choice. Bottom: 3D reconstructions under various model assumptions. The red curve in all panels represents the fiducial model parameters: vertical magnetic field (Bz), CW rotation and Keplerian orbit (fK = 1.0). The global minimum for each curve is highlighted by a horizontal dashed line in the respective colour. Left: three different magnetic field configurations: vertical, radial and toroidal (subscripts z, r and ϕ, respectively). The recovered 3D under a radial magnetic field appears spread out rather than as a compact hotspot-like structure. That being said, consistent with the analysis of refs. 11,13, vertical magnetic fields, which do result in a compact hotspot-like structure, are favourable according to this metric, with lower validation-χ2 around θo = 12°. Centre: a comparison of CW and CCW angular velocity models. Consistent with the analysis of ref. 13, a CW rotation is preferred across all inclination angles. Right: a Keplerian orbit has the lowest validation-χ2 fit across three different fractions of sub-Keplerian orbit: fK = 1.0, 0.9 and 0.8. The recovery under fK = 0.9 (bottom right) is broadly consistent with the Keplerian model, with a tendency towards smaller radii (illustrated by the top-view panel).
