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The nature of the emission region around Sagittarius A* (Sgr A*), thesupermassive black hole at the Galactic Center, remains under debate. Aprediction of jet models is that a frequency-dependent shift in the position ofthe radio core (core-shift) of active galactic nucleii occurs when observingemission dominated by a highly collimated relativistic outflow. We usemillimeter Very Long Baseline Interferometry to study the frequency-dependentposition of Sgr A*'s radio core, estimate the core-shift for different emissionmodels, investigate the core-shift evolution as a function of viewing angle andorientation, and study its behaviour in the presence of interstellarscattering. We simulate images of the emission around Sgr A* for accretioninflow models (disks) and relativistic outflow models (jets). They are based onthree-dimensional general relativistic magnetohydrodynamic simulations. Wecreate flux density maps at 22, 43 and 86 GHz sampling different viewing anglesand orientations, and examine the effects of scattering. Jet-dominated modelsshow significantly larger core-shifts (in some cases by a factor of 16) thandisk-dominated models, intermediate viewing angles (i=30, 45 degrees) show thelargest core-shifts. Our jet models follow a power-law relation for thefrequency dependent position of Sgr A*'s core. Their core-shifts decrease asthe position angle increases from 0 to 90 degrees. Disk models do not fit wella power-law relation and their core-shifts are insensitive to changes inviewing angle. We place an upper limit of 241.65 +-1.93 microarcseconds per cmfor the core-shift of jet models including refractive scattering. Our jetmodels agree with earlier predictions of AGN with conical jets, and thecore-shift is retrievable even in the presence of interstellar scattering.

The Core-shift of Sagittarius A* as a Discriminant between Disk and Jet Emission Models with millimeter-VLBI