Constraining the absolute motion of the Near-IR counterpart to Sagittarius A*

Constraints on the reflex motion of Sagittarius A* (Sgr A*) can be used to constrain the dynamical center of the Galaxy and whether Sgr A* has an intermediate-mass black hole companion. One promising way to measure this is using the near-infrared (NIR) counterpart of Sgr A*. Using Gaia, HST, and Keck Adaptive Optics observations, we present the first measurement of the NIR reflex motion of Sgr A* in an absolute reference frame. We place 25 years of Keck measurements of Sgr A*-IR into the Gaia ICRS reference frame using HST observations of Gaia sources at the Galactic Center. The NIR astrometric reference frame for the Galactic Center has historically been constructed relative to seven infrared-bright SiO masers that have extremely accurate radio positions, measured in the Sgr A*-radio component rest frame. Constraining the NIR motion of Sgr A* in the Gaia ICRS reference frame removes dependence of the measurements on the transformation accuracy between radio and NIR observations. This allows us to measure the reflex motion of Sgr A* that is independent from other methods such as the radio or through stellar orbits.