Avery Broderick (Perimeter Institute) and Avi Loeb (Harvard) have modeled SgrA* using Radiatively Inefficient Accretion Flows (RIAF), and then created images including full GR ray-tracing. We've collaborated with them to fit RIAF models to the 1.3mm VLBI data on SgrA* to estimate parameters of the SgrA* black hole and accretion disk.RIAF models are first constrained to fit the overall Spectral Energy Density of SgrA*, then fit to the 1.3mm VLBI data. Model parameters include black hole spin, accretion disk inclination, and black hole spin axis orientation on the sky. First modeling efforts with the April 2007 data set set limits on disk inclination, and when data from April 2009 are included, limits on black hole spin also become significant.


Broderick, Fish, Doeleman, Loeb, ApJ, v697, pp 45-54 (2009), "Estimating the Parameters of Sagittarius A*'s Accretion Flow Via Millimeter VLBI"

Broderick, Fish, Doeleman, Loeb, ApJ, v735, id 110 (2011), "Evidence for Low Black Hole Spin and Physically Motivated Accretion Models from Millimeter-VLBI Observations of Sagittarius A*"


Best fit models for SgrA*: (Left) Chi-squared map of RIAF models fit to 2007 and 2009 1.3mm VLBI data as a function of black hole spin and accretion disk inclination. The spin is less than 0.86 at 2-sigma significance, and the disk inclination is 68 degrees (+9, -28; 2-sigma). (Right) Image of the best fit RIAF model for SgrA*.

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Massachusetts Institute of Technology